DOCUMENT REVIEW

ARIZONA TRANSPORTATION RESEARCH CENTER

2739 E. Washington, Phoenix, AZ 85034; Mail Drop 075R; ph. 602-712-3137; Fax 602-712-3400

e-mail jsemmens@dot.state.az.us; internet http://www.dot.state.az.us/about/atrc/

MAY 2000

ANNOTATED TABLE OF CONTENTS

 

Topic

Title

ADM/
research

Seven Keys to Building a Robust Research Program NCHRP Synthesis 280 by Thomas Deen and Barbara Harder (Transportation Research Board, 2101 Constitution Ave. NW, Washington, DC 20418; phone: (202) 334-2934; http://www.nas.edu/trb ) (1999)[TE7.N36#280] Factors that add up to an improved research program are outlined.

CON/
embankment

Embankment Widening Design Guidelines and Construction Procedures by Richard Deschamps, et al. (School of Civil Engineering, Purdue University, W. Lafayette, IN 47907-1284; phone (765) 494-4600; http://www.purdue.edu ) (Sept. 1999)[TD 100:IN 99-4] Factors that influence the ultimate stability of widened embankment slopes are outlined.

CON/
soils

Measuring In Situ Mechanical Properties of Pavement Subgrade Soils by David Newcomb and Bijorn Birgisson (Transportation Research Board, 2101 Constitution Ave. NW, Washington DC 20418; phone (202) 334-2934; http://www.nas.edu/trb )(1999)[ TE7.N36 #278] Strength of the subgrade is one of the three primary inputs to pavement design; the other two are traffic and the environment.

CON/
INOV

Use of Design/Build and Warranties in Highway Construction by Ann Johnson, (MnDOT, Office of Research, 395 John Ireland Blvd, Mail Stop 330, St. Paul, Mn 55155;phone (612) 282-2267; http://www.dot.state.mn.us ) (Oct 1999)[TD100:MN 99-37] The key advantages are (1)motivating the contractor to provide a higher quality product, (2)encouraging innovation by the contractor, and (3)reducing the need for agency resources.

ENV/
impacts

Indicators of the Environmental Impacts of Transportation (Environmental Protection Agency, Washington, D.C. 20460; http://www.epa.gov ) (Oct. 1999) [EP1.2:1N2/18] On-road vehicle emissions have fallen since the 1970s despite the rapid growth in vehicle travel.

MAIN/
snow

Improved Visibility for Snow Plowing Operation by J.D.Bullough, et al. (Rensselaer Polytechnic Institute, 110 8th St., Troy, NY 12180; ph. 518-276-6000; http://www.rpi.edu ) (Dec 1999)[E220.5B8I4] Aerodynamic, lighting and signaling recommendations are made. These recommendations can be readily incorporated into the purchasing and performance specifications of winter maintenance agencies.

PAVE/
rehabilitation

"Cost-Effective Rehabilitation of Portland Cement Concrete Pavement in Nevada" by Sohila Bemanian and Peter Sebaaly in Transportation Research Record 1684 (Transportation Research Board, 2101 Constitution Ave, NW, Washington DC 20418; ph. 202-334-2934; http://www.nas.edu/trb ) (1999)[TE7.H5#1684] A hot mix asphalt overlay is considered the most feasible and cost-effective option for rehabilitating PCC pavements.

PAVE/
concrete

Durability of Concrete (Transportation Research Board, 2101 Constitution Ave, NW, Washington DC 20418; ph. 202-334-2934; http://www.nas.edu.trb ) (1999)[TE1.H53#494] Factors affecting the durability of concrete and remedies for problems are outlined.

PAVE/
shoulder

Evaluation of Pavement Shoulders by Khalel Ksaibati and Israel Crowe (Department of Civil Engineering, University of Wyoming, Laramie, Wyoming 82071-3295; ph.307-766-4253; http://www.eng.uwyo.edu/ce.html ) (May 1999) [TE212.5.k73] Significant reductions in accidents can be expected when shoulder widths are increased or if shoulders are added. On roadways with very low traffic volumes increasing the shoulder width results in an insignificant reduction of accidents.

PAVE/
rehab

"Longevity of Diamond-Ground Concrete Pavements" by Shreenath Rao; et al. in Transportation Research Record 1684 (Transportation Research Board, 2101 Constitution Ave., NW, Washington DC 20418; ph. 202-334-2934; http://www/nas.edu/trb ) (1999)[TE7.H5#1684] Grinding costs substantially less that an overlay, can be accomplished during off-peak hours with short lane closures, and can be performed without having to close adjacent lanes.

PAVE/
smooth

Measuring, Achieving, and Promoting Smoothness of Virginia’s Asphalt Overlay by Kevin McGhee (Virginia Transportation Research Council, 530 Edgemont Rd., Charlottesville, VA 22903; ph. 804-293-1900; http://www.vdot.state.va.us/vtrc ) (April 1999) [TD100:VA99-19] Only three variables significantly influence the achievable smoothness of an overlay: (1)the roadway functional classification, (2)the ride quality of the original (underlying) pavement, and (3)whether the overlay was subject to the provision for smoothness.

RDSD/
rest areas

Rest Area Forum: Summary of Proceedings by Patricia Hamilton (Turner Fairbank Highway Research Center, 6300 Georgetown Pike, McLean, VA 22101-2296; http://www.tfhrc.gov ) (Dec 1999)[TD2.30:00-3-034] Recommendations include: improve safety and security, support privately owned truckstops, use alternative parking sites, improve provision/location of public rest areas and privately owned truckstops, improve financial support, eliminate and enforce time limits, and increase driver education and information.

SAFE/
pedestrian

"Analysis of Factors Contributing to ‘Walking Along Roadway’ Crashes" by Patrick McMahon, et al. in Transportation Research Record 1674 (Transportation Research Board, 2101 Constitution Ave, NW, Washington, DC 20418; ph. 202-334-2934; http://www.nas.edu/trb ) (1999) [TE7.H5#1674] Absence of sidewalks, higher traffic volume, higher vehicle speed, and smaller width of unpaved shoulder increase the likelihood of a walking-along-roadway pedestrian crash.

SAFE/
fatigue

Automatic Detection of Driver Fatigue, phase III by Sarbjit Singh Kaur, et al. (University of Minnesota, Department of Computer Science, Artificial Intelligence Laboratory, 4-192 EE/CS Bldg. – 200 Union Street, SE, Minneapolis, MN 55455-0159; ph. 612-625-8544; http://www.umn.edu ) (Jun 1999) [TD100:MN99-30] In-vehicle devices for detecting driver fatigue are described.

SAFE/
signals

"Can We Make Red-Light Runners Stop? Red-Light Photo Enforcement in San Francisco, California" by Jack Fleck and Bridget Smith in Transportation Research Record 1693 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb ) (1999)[TE7.H5#1693] Photo enforcement has shown that it can increase public safety in a revenue neutral manner. Experience shows that engineering solutions should be considered first.

SAFE/
mobile phones

"Driving and Using Mobile Phones: Impacts on Road Accidents" by P.A. Koushki, et al. in Transportation Research Record 1694 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb ) (1999)[TE7.H5#1694] The risk involved in the use of mobile phones while driving was similar to the hazard associated with driving with a blood alcohol level at the legal limit.

SAFE/
TRK

"Effects of Heavy Vehicle Mechanical Condition on Road Safety in Quebec" by Michel Gore, et al. in Transportation Research Record 1686 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb ) (1999) [TE7.H5#1686] Heavy vehicles with major non-complying components have a propensity to be involved in accidents that is five times higher.

SAFE/
TECH

"Effects of Weather-Controlled Variable Speed Limits and Warning Signs on Driver Behavior" by Pirkko Rama in Transportation Research Record 1689 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb ) (1999) [TE7.H5#1689] The system proved to be more effective when the adverse weather and road conditions were not easy to detect. The speed reductions were not sufficient to make the VMS system economical on low volume roads.

SAFE/
age

"Impact of Passengers on Young Driver Safety" by Brian Aldridge, et al. in Transportation Research Record 1693 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb )(1999)[TE7.H5#1693] Vehicle accident propensity for young drivers with peers increases with the number of people in the vehicle.

SAFE/
mobile phones

Investigation of the Uses of Mobile Phones While Driving by Alastair Cain and Mark Burris (Center for Urban Transportation Research, College of Engineering, University of South Florida, 4202 E. Fowler Ave, CVT100, Tampa, Fl. 33620; ph.813-974-3120; http://www.usf.edu ) (Apr 1999)[TL152.3.C34] People who used a mobile phone while driving were anywhere from 34% to 300% more likely to have an accident.


Seven Keys to Building a Robust Research Program NCHRP Synthesis 280 by Thomas Deen and Barbara Harder (Transportation Research Board, 2101 Constitution Ave. NW, Washington, DC 20418; phone: (202) 334-2934; http://www.nas.edu/trb ) (1999)[TE7.N36#280]

 

Highlights

  • the 7 keys are…

1.      found it on trust

2.      market boldly

3.      root it in economics

4.      make deals unabashedly

5.      insist on accountability

6.      embrace policy research

7.      empower the staff

Found it on Trust—The most important of the seven keys is the establishment of a trust relationship between the research unit and its parent organization. When trust exists, there is a feeling of confidence, an assurance of shared goals, of being on the same team. Developing trust takes time, and can be fostered through a variety of attitudes and activities. The feeling extends in both directions, from upper management down to research, and from the research program up to management. It can be injured by the careless or inattentive of either party. With trust a program will likely prosper; without will become marginalized and ineffective, notwithstanding its other strengths.

Market Boldly—Marketing is an essential component of a robust research program. It is not an activity that comes naturally to many researchers, nor is it readily understood or always embraced as an appropriate part of the job. Without it, there are just too many forces pushing toward the neglect of this activity. The research manager must step forward and become an effective research advocate.

Marketing is needed at every stage of the process: in the solicitation of problems, in anticipating research needs, in justifying the time and budget required, in persuading others to test the product, in arguing for deployment, in advertising successful products, and in selling the overall need for research managers to use a variety of methods to accomplish this. Marketing needs to be seen by both top management and research management as a vital part of the research function.

Root It in Economics—Robust research programs look to economic justification for their activities. Top DOT managers, as public officials, are necessarily concerned with the economic use of taxpayer resources. In contrast, researchers are frequently selected primarily for their technical expertise. However, technical interest and enthusiasm, although; laudable, are usually secondary to economic considerations when making research program decisions, or justifying the funding needed for implementation. Managers of robust programs are sensitive to the need to use economic rationale to ensure appropriate programs and their justification.

Make Deals Unabashedly—Directors of robust programs are bold in their cultivation of alliances of all types. Programs can often be enhanced by actively working to establish relationships with appropriate and compatible research entities.

Insist on Accountability—Robust research organizations are accountable for their use of resources and their output. Research is especially vulnerable to a lack of accountability. Accountability is a two-way street—top managers perform their duties while research managers deliver programs that contribute to agency goals. In addition, top manager should be accountable as well. Failure to do so gradually erodes trust in the program, and it becomes irrelevant to the parent unit..

Embrace Policy Research—Robust transportation research programs include policy research in addition to technical research in their portfolios. Policy research provides a communications channel between research and top management. This channel is important because of the window it provides to the research manager to better understand the challenges facing the parent organization and thus to steer the research program in relevant directions. Policy issues are at the center of top management concerns and constitute the major challenges to the accomplishment of the state transportation function. Policy research can have a positive impact by better informing management decisions. Policy research also provides the opportunity for the research manager to sell the benefits of more traditional technical research to top management and to strategically access the research role and long-term program within the parent department. A research unit that does not include policy research will have a more difficult task in marketing its usefulness to a top management concerned primarily with policy issues.

Empower the Staff—A robust research program must deliver quality products in a timely manner. Research tasks by their nature require a climate that fosters the generation of a flow of novel ideas. Idea generation is enhanced by interaction with other individuals working on similar problems in a variety of settings. Accordingly, researchers need to feel free to interact with others across organizational lines, either indirectly or face to face; have the opportunity to travel when required to interact with researchers working on similar problems in other organizations; and become familiar with potentially researchable problems of parent units.


 

Embankment Widening Design Guidelines and Construction Procedures by Richard Deschamps, et al. (School of Civil Engineering, Purdue University, W. Lafayette, IN 47907-1284; phone (765) 494-4600; http://www.purdue.edu )(Sept. 1999)[TD 100:IN 99-4]

 

Highlights

·         successful widening requires:

  • construction of benches into the original embankment;
  • adequate compaction of fill; and,
  • control of drainage.
  • coarse-grained soils are not suitable for construction of widened embankments
  • sloughing is attributed to poor compaction and/or saturation of the slope
  • in all cases, the slopes would have been stable if the INDOT Standard Specifications had been followed

            There are a number of factors that influence the ultimate stability of widened embankment slopes. These include: removal of vegetation and construction of benches in existing embankments; achieving adequate compaction and shear strength of fill soils; achieving compatibility in the permeability of fill materials; controlling surface water runoff; considering the ultimate ground water flow regime; and considering the required final inclination of the embankment slope. Although all of these factors can be related in some degree to the cases investigated, the overriding factor contributing to the failures appears to be a lack of appreciation of the potential for failure by the personnel involved.

            For the failed sites, little, if any, documentation was available that would indicate that the stability of the final constructed slopes had been considered. In general, there were no construction or "as built" drawings of the embankment slopes, and few, if any, quality control tests were performed outside of the right-of-way. In all cases, the slopes would have been stable if the INDOT Standard Specifications had been followed. It appears that in most cases the parties involved felt that the volume of fill placed did not warrant the extensive earthwork that would have been necessary to meet the specifications. Therefore, educating both INDOT technical personnel and earthwork contractors regarding the potential for such failures to occur is viewed as crucial to the ultimate success of these types of projects.

            The results of the investigations indicate that failure of these widened embankments resulted from sub-standard compaction of fill, and inadequate benching into the original embankment. Surface water infiltration from the roadway run-off contributed to the problem, possibly saturating and softening the soils. These conclusions confirm the responses of the survey conducted of federal and state transportation agencies. Survey respondents indicated that successful widening requires:

            Construction Plans for successful projects indicate that benching was performed even when the fills were minor, in some cases 0.3m or less in thickness. The compaction data available for these projects, although considered insufficient, tends to indicate that soils were compacted when placed. Control of surface water run-off from the roadway may have contributed to the success of the U.S. 421 widening project.

            Erodible, coarse-grained soils are not suitable for construction of widened embankments unless encased in less pervious soils. Erosion undercuts vegetation and permits infiltration of water into the slope. When the original embankment soils are of lower permeability, the infiltrating water can become perched and cause soils to soften and lose strength.

            Sloughing is attributed to poor compaction and/or saturation of the slope. Better management of surface water run-off will reduce surface erosion and sloughing; thereby, reducing slope maintenance costs. Where slopes are steeper than recommended, site specific analysis is need to consider overall stability and sloughing stability of the slope.

            Since the slope failures investigated would not have occurred if INDOT Standard Specifications were followed, it appears that the primary cause of failure is the lack of appreciation of the potential risk by the parties involved, both INDOT and construction personnel. Very little quality control testing was performed in the compacted soils comprising the widened embankment material even on the successful projects. No quality control testing was performed on the failed sections. One of the reasons for limited quality control testing on these projects may be limited availability of INDOT personnel for this purpose on smaller sized projects. It is imperative that the news from these failures, and all failures for that matter, be brought to the attention of INDOT engineers and technicians throughout the state so that they can become aware of the potential for failure, and prioritize their time for quality control testing when time is limited.


Measuring In Situ Mechanical Properties of Pavement Subgrade Soils by David Newcomb and Bijorn Birgisson (Transportation Research Board, 2101 Constitution Ave. NW, Washington DC 20418; phone (202) 334-2934; http://www.nas.edu/trb )(1999)[ TE7.N36 #278]

 

Highlights

  • most state agencies use the 1993 AASHTO pavement design guide
  • a number of agencies employ mechanistic-empirical analysis as a secondary method of flexible pavement structural design
  • strength of the subgrade is one of the three primary inputs to pavement design; the other two are traffic and the environment
  • subgrade spatial and seasonal variabilities are important considerations in pavement design
  • in situ characterization of subgrade soils is critical to the realistic design of pavement structures

This synthesis presents a review of the practice for characterizing the mechanical properties of pavement subgrade in situ. The practices of highway agencies in the United States, Canada, Austria, Belgium, Finland, Iceland, Norway, and Switzerland with respect to in situ subgrade testing are summarized and discussed. The primary topics are the tests conducted to estimate soil mechanical properties of strength and stiffness and these are discussed in the context of design procedures, factors affecting mechanical properties, and the variability of measurements.

A questionnaire was prepared and distributed to the participating agencies in order to provide and overall picture of practice. This questionnaire was divided into four major parts: (1) Flexible Pavement Design, (2) Rigid Pavement Design, (3) laboratory Testing of Soils, and (4) In Situ Testing of Soils. The survey was devised to document the type of pavement design practices in use, parameters within the design procedures used to describe the subgrade, the type of laboratory testing used, and, most importantly, the type and frequency of in situ testing performed on soils. The results of this survey were incorporated into general discussions of subgrade testing and interpretation that was based on a review of the literature.

The survey showed that most state agencies in the United States use the 1993 American Association of State Highway and Transportation Officials (AASHTO) pavement design guide for both flexible and rigid pavements. However, it is significant that a number of agencies employ mechanistic-empirical analysis as a secondary method of flexible pavement structural design. For both the 1993 AASHTO and mechanistic-empirical flexible pavement design procedures the parameter used to describe the subgrade is resilient modulus. The other primary flexible pavement design procedures involve test results that are indicative of the shear strength, namely the R-value or California Bearing Ratio (CBR). Subgrades for rigid pavements are almost universally characterized by the modulus of subgrade reaction (k-value), sometimes known as a liquid foundation. The ASSHTO rigid pavement design procedure allows for the estimation of the k-value by means of a nomograph, which uses subgrade modulus, base modulus, and base thickness. The strength or stiffness of the subgrade is one of the three primary inputs to the pavement design process; the other two being traffic and the environment. Adequately and realistically characterizing this material is critical to the success of the pavement system.

It is clear that the state of stress, moisture content, state of moisture (frozen or thawed), and density all have effects on the properties of soils. The state of stress defines the magnitude of loading and the degree of confinement for the soil. There are numerous models that describe the relationship the state of stress and stiffness of the soil, but it is generally acknowledged that soils soften with increasing stress and the granular soils stiffen. Moisture content may cause the material to soften or weaken with increasing amounts of water, depending on the particular soil type. The state of moisture, however, can have a counter effect because frozen soils will support more load than those containing thawed water. Increasing density contributes to soil strength or stiffness, but its effect must be considered along with moisture content. Thus, in testing it is important to have a clear understanding of the in situ conditions.

Deflection testing is the most popular means of evaluating pavement structures for the agencies surveyed. Although the majority of the agencies employ falling weight deflectometers (FWD) for this purpose, high-speed deflectometers are now being used. Most of the states, provinces, and European countries reviewed use deflection parameters such as the maximum deflection or subgrade modulus calculation. Some states use an equation to relate FWD maximum deflection to the Benkelman beam deflection. A surprising number of agencies use backcalculation techniques to estimate layer moduli in the interpretation of deflection measurements. Other types of in situ tests in common use include small-load techniques and intrusive approaches. The small-load methods provide measures of soil stiffness and include the Finnish Loadman, the spectral analysis of surface waves (SASW), and the Soil Stiffness Gauge. Of these, only the SASW is currently used by any of the states on a routine basis. Intrusive techniques include the dynamic cone penetrometer (DCP), the borehole pressuremeter, the standard penetration test (SPT), cone penetration testing, miniature cone penetrometer, dialatometer testing, vane shear testing, and field CBR testing. The most popular of these methods are the DCP and the SPT. Both of these tests are relatively simple and provide a good indication of the soil shear strength.

Subgrade spatial and seasonal variabilities are important considerations in pavement design. Sampling frequencies for the purpose of design are based on the type of soil, traffic volume, and the difficulty of testing and analysis. Statistical techniques exist to assist engineers in determining the appropriate frequency of testing, and these should be employed. Furthermore, it would be wise for agencies to investigate subgrade spatial variability within their jurisdictions. Seasonal variability of subgrade properties is a regional issue that may be addressed by a combination of reviewing historical records and establishing a testing program to provide the needed data. Data for determining the patterns of seasonal variability may be obtained from facilities such as the Minnesota Road Research project and studies such as the Long-Term Pavement Performance program.

In situ characterization of subgrade soils is critical to the realistic design of pavement structures. A number of means exist to provide such information and these should be exploited to provide timely and accurate input to the process of pavement design and the monitoring of pavement performance.


Use of Design/Build and Warranties in Highway Construction by Ann Johnson, (MnDOT, Office of Research, 395 John Ireland Blvd, Mail Stop 330, St. Paul, Mn 55155;phone (612) 282-2267; http://www.dot.state.mn.us ) (Oct 1999)[TD100:MN 99-37]

 

Highlights

  • several states have implemented short-term pavement warranty projects
  • Wisconsin and Michigan have instituted very successful warranty programs
  • the key advantages are…
  • motivating the contractor to provide a higher quality product
  • encouraging innovation by the contractor
  • reducing the need for agency resources

Staff and funding reductions, along with additional constraints on staff time have created the need for agencies to find alternative contracting methods. Requiring warranties on roadway construction may help to solve this problem.

Nationwide, several states have implemented short-term pavement warranty projects. Additional curiosity about warranty contracts has recently developed when private industry began promoting long-term warranties of 15 years and more. This type of warranty was recently used in New Mexico on the $295 million highway project that required the contractor to design, build, and warranty the project. The 20-year pavement warranty for this project cost $62 million.

Several models are available for successful warranty programs. Both Wisconsin and Michigan Departments of Transportation have instituted very successful warranty programs. Lessons learned from their experiences could be used to initiate programs elsewhere, both at a state and local level.

There are many advantages and benefits to requiring warranties on highway construction, including motivating the contractor to provide a higher quality product, encouraging innovation by the contractor, and reducing the need for agency resources, including inspection and maintenance. Other potential benefits include:

·         Increased product quality with a resulting lower life-cycle cost.

·         Lowered risk to the owner by providing assurance that the contractor will correct early failures that may have escaped notice during traditional construction.

·         Increased involvement by contractors in the planning and process leads to fewer claims and disputes, better bids, products and reduced risk of liability losses for everyone.

·         Encourages the development of better testing equipment and techniques for construction, including more uniform best construction practices.

·         Larger, qualified, stable firms may develop to do all tasks for major transportation projects. This may lessen the risk to both owners and sureties for large projects.

Along with the benefits of using warranties, there are also some concerns:

·         The impacts of warranties on initial and total life-cycle costs of facilities may negate any maintenance savings.

·         Agency uncertainty regarding the ability to administer contracts with warranties and to enforce them over extended periods.

·         Warranties are only as good as the contractor and the surety company involved. Issues of particular concern include obtaining warranty work action if the contractor goes out of business.

·         Uncertainty of whether surety companies will provide long-term bonding guarantees required for warranties on large projects, which carry much larger risks.

·         Small or minority contractors may be eliminated from bidding process if they are unable to acquire bonding.

Recommendations

·         Agencies should begin issuing pilot-type contracts requiring a minimum two-year warranty on workmanship and materials for appropriate contract items.

·         Agencies should specify projects that are appropriate for use as pilot projects, impose a warranty on those projects, and study the effects of warranties for a trial period.

·         Use the Wisconsin specifications as a model.

·         Staff should be trained to conduct pavement condition surveys. This will allow the condition of the pavement to be monitored and reasons for distress to be understood.

·         Bid security for warranty contracts should be large enough to cover the highest reasonable expenditures that can be expected from warranty failure.

·         A sample specification should be developed and made available to local agencies for use in developing and letting warranty projects. This specification should include all items subject to warranty, and be easy to use on a variety of projects.

·         Projects selected for warranty contracts should focus on the pavement structure, including base and subbase.

·         Given present construction conditions, total Design/Build/Warranty programs may offer some solutions. However, in their present form they would be difficult to fund and administer. Additional research should be conducted regarding their use given construction and legal contract constraints.


Indicators of the Environmental Impacts of Transportation (Environmental Protection Agency, Washington, D.C. 20460; http://www.epa.gov ) (Oct. 1999) [EP1.2:1N2/18]

 

Highlights

  • emissions control equipment has significantly reduced the rate at which vehicles emit pollutants
  • vehicle emissions standards and reformulated and oxygenated fuels have led to significant progress at controlling vehicle emissions
  • on-road vehicle emissions have fallen since the 1970s despite the rapid growth in vehicle travel

Road vehicle travel is the dominant form of transportation in the United States. In 1997, about 2.56 trillion vehicle miles were traveled on U.S. roads by passenger cars, motorcycles, buses, light-duty trucks and heavy-duty trucks. Vehicle travel has increased rapidly – rising from 719 billion miles in 1960.

Air pollution from motor vehicles is the most widely recognized and studied environmental impact of transportation. Air pollution from vehicle travel comes from byproducts of the combustion process and evaporation of unburned fuel, as well as particulate matter that is entrained by passing automobiles. Vehicle travel also causes other adverse effects, such as greenhouse gas emissions, noise problems, collisions with wildlife, and water quality impacts from oil leaks. Hazardous materials incidents during highway transport may release harmful chemicals to the environment.

On-road vehicle travel results in emission of pollutants that are harmful to human health and welfare. Carbon monoxide (CO), sulfur oxides (SOx), oxides of nitrogen (NOx), volatile organic compounds (VOC), and particulate matter (PM) are by-products of the internal combustion process and are emitted directly from vehicle exhaust. VOCs are also emitted during fuel evaporation. Evaporation occurs from vaporization of gasoline during travel (running losses), after parking while the engine is still warm (hot soak), vapors escaping while refueling the vehicle, and even as a vehicle sits parked while the engine is cool on hot summer days (diurnal emissions).

Toxic air pollutants are also emitted by motor vehicles. Many toxic air pollutants are emitted in the form of particulates or VOC. Major hazardous air pollutants emitted by motor vehicles include Acetaldehyde, Benzene, 1,3-Butadiene, Formaldehyde, Toluene, and Xylenes.

Modern emissions control equipment has significantly reduced the rate at which vehicles emit pollutants from the tailpipe. Lead emissions have been virtually eliminated due to the phase-out of leaded gasoline. Increasingly stringent vehicle emissions standards and reformulated and oxygenated fuels have led to significant progress at controlling vehicle emissions. In fact, on-road vehicle emissions have fallen since the 1970s despite the rapid growth in vehicle travel.

Factors that affect the amount of emissions coming from a motor vehicle include:

Factors that influence the amount of environmental damage that occurs from air pollutant emissions include:

 

Air Pollutant Emissions from Autos

(in tons per year)

Year

VOC

NOX

CO

PM10

PM2.5

SO2

Lead

1970

9,193

4,158

64,031

225

 

132

142,918

1975

7,248

4,725

59,281

207

 

158

106,868

1980

5,907

4,421

53,561

120

 

159

47,184

1985

5,864

3,806

49,451

77

 

146

13,637

1990

3,947

3,220

37,407

61

37

138

314

1995

3,426

3,444

33,701

62

36

143

14

1997

2,755

2,875

27,036

56

32

129

12

 


Improved Visibility for Snow Plowing Operation by J.D.Bullough, et al. (Rensselaer Polytechnic Institute, 110 8th St., Troy, NY 12180; ph. 518-276-6000; http://www.rpi.edu ) (Dec 1999)[E220.5B8I4]

 

Highlights

  • poor visibility reduces operational safety and contributes significantly to the hazards
  • aerodynamic, lighting and signaling recommendations are made
  • these recommendations can be readily incorporated into the purchasing and performance specifications of winter maintenance agencies

Snow and ice control may be the most hazardous duty faced by highway maintenance crews on a regular basis. This work frequently requires long work hours, often at night during extreme weather conditions. Forward visibility is reduced during snowplowing operations by a combination of factors including glare from reflected headlight illumination, obscured windows, and blowing snow. These factors vary with climatic conditions and are often influenced by features of the plow, the vehicle, and its lighting systems. Poor visibility reduces operational safety and contributes significantly to the hazards faced not only by the snowplow operators, but also by motorists traveling on the road being plowed. Some states have noted serious accidents involving snowplows and vehicles entering the plow’s snow cloud.

The snowplow operator and other motorists experience reduced visibility when light powder snow overspills the plow and is caught in the vehicle air stream. The snow continues around the truck body until being caught in the turbulence immediately behind the vehicle. The snow cloud obscures the rear of the truck and created a hazardous condition for other motorists. While plowing, the air stream can carry the snow to the snowplow windshield, decreasing the operator’s visibility. At night, light from standard headlights mounted above the plow and reflected toward the operator created a dynamic, white veil in front of the operator, which further reduces the operator’s visibility. This report documents research conducted through the National Cooperative Highway Research Program (NCHRP) to provide for safer snow plowing operations by improving visibility for both the snowplow operator and other motorists in close proximity to the vehicle plowing snow.

Aerodynamic Recommendations

Lighting and Signaling Recommendations

The first two lighting recommendations were demonstrated in the field to result in low back-scatter luminances and improved visibility from the viewing position of the snowplow operator. The third improved closure detection times for drivers of other vehicles in the vicinity of the plow.

Both the aerodynamic and lighting recommendations described above are a result of the review of literature, development of visibility models, laboratory tests and measurements, and demonstrations of the most promising solutions in the field. Each of these activities reinforced the others and resulted in consistent findings. These solutions are simple, practical and can be readily incorporated into the purchasing and performance specifications of winter maintenance agencies in North America.


"Cost-Effective Rehabilitation of Portland Cement Concrete Pavement in Nevada" by Sohila Bemanian and Peter Sebaaly in Transportation Research Record 1684 (Transportation Research Board, 2101 Constitution Ave, NW, Washington DC 20418; ph. 202-334-2934; http://www.nas.edu/trb ) (1999)[TE7.H5#1684]

 

Highlights

  • many portland cement concrete sections have met or exceeded their design life
  • the most common form of PCC pavement rehabilitation is overlaying with hot-mix asphalt
  • rubblization had been used successfully on continuously reinforced concrete pavement
  • crack, seat and rubblization have approximately the same life-cycle cost over a 35-year analysis period

Approximately 804,700 lane-km of portland cement concrete (PCC) pavement are included in the nation’s highway system. On the basis of a recent study, many of these sections have met or exceeded their design life and are in need of major rehabilitation.

There are 1400 lane-km of PCC pavement on Nevada Interstates. More than 50% of these will require major rehabilitation within the next 5 years. Because of limited funding, and more demand for the use of these funds, the proper selection of cost-effective rehabilitation strategies for PCC pavements is needed now more than ever before.

Until recently, the Nevada Department of Transportation (NDOT) did not have any experience with major rehabilitation techniques for PCC pavements. In 1992, NDOT launched a comprehensive research effort to evaluate cost-effective concrete repair strategies throughout the state.

The most common form of PCC pavement rehabilitation is overlaying with hot-mix asphalt (HMA). Although HMA overlays are commonly used, their performance is often less than satisfactory because of reflection cracking, which significantly reduces pavement serviceability. Reflection cracking in HMA overlays is caused by thermal- and traffic-induced stresses. Expansion and contraction of the PCC pavement results in horizontal movements that produce strains in the HMA surface that exceeds its tensile strength. Traffic loads can cause vertical differential movements at the location of the joints and cracks in the PCC slab and can induce shear strains throughout the HMA layer. If the HMA immediately over the joints and "working" cracks in the PCC is not able to accommodate these localized movements, reflective cracking develops.

Several surface preparation techniques have been used before placing an HMA overlay in attempts to minimize reflection cracking. Some of the most common techniques are rubblization, crack and seat or break and seat and saw and seal. This paper addresses the structural design, construction techniques, and performance of the rubblized pavement.

Rubblization is a technique used to eliminate reflective cracking in HMA overlays through total destruction of the existing concrete slab. This technique is applicable when there is little potential for retaining either significant slab integrity or the structural capacity of the original pavement. Rubblization had been used successfully on continuously reinforced concrete pavement (CRCP) having substantial deterioration in the form of punchouts and patching. The designer must be aware of, and account for, the significant reduction in the structural capacity of the existing PCC pavement caused by rubblization. This technique is reasonably new, and it has only recently been used by a few states.

After extensive research and 4 years of field performance data, an HMA overlay is considered the most feasible and cost-effective option for rehabilitating PCC pavements. On the bases of this study, the following conclusions were reached regarding the I-80, Elko, projects:

·         After 4 years, the functional and structural performance of the pavements indicate both the cracked and seated and the rubblized sections are performing equally well. The ride quality, rut depths, and structural capacities of both techniques are still rated within the good to excellent range.

·         Rubblization and crack and seat are effective methods for delaying reflective cracking if designed and constructed properly. However, their long-term performance in Nevada still must be analyzed.

·         Structural coefficient for the rubblized layer increases with time, One possible explanation is the rubblized PCC pavement is becoming more confined. This is an extremely important finding. Increases in the structural coefficient will provide increases in the load-carrying capacity of the pavement. The length of time this will continue to occur has yet to be determined.

·         Empirical design procedures should be used to determine the initial overlay thickness. However, deflection measurements should be taken after the project is completed to verify the design assumptions. Structural coefficient values should be adjusted accordingly on the basis of the deflection values.

·         On the basis of initial construction costs, the crack and seat project had the lowest initial cost approximately $212,000 per km, followed by rubblization with an approximate cost of $324,000 per km, and reconstruction costing approximately $1,243,000 per km. However, on the basis of projected future performance, both crack and seat and rubblization have approximately the same life-cycle cost over a 35-year analysis period.


Durability of Concrete (Transportation Research Board, 2101 Constitution Ave, NW, Washington DC 20418; ph. 202-334-2934; http://www.nas.edu.trb ) (1999) [TE1.H53#494]

 

Highlights

  • factors affecting the durability of concrete and remedies for problems are outlined

When used in transportation, the performance of concrete is generally regarded as satisfactory if it meets the contractual requirements for composition, slump, and strength and thereafter is found to be "durable". There is a misconception that concrete has a property named "durability". This is not the case, since a given concrete with a given set of properties will endure without noticeable change for centuries or even millennia in one environment and be reduced to fragments in a few years or even a few months in another. Durability includes a series of properties required in a particular environment to which concrete will be exposed in service life. Durable concrete is concrete that in the particular environment of service resists the forces in that environment that tend to cause it to disintegrate without requiring excessive effort for maintenance during its service life.

 

Type of Materials-Related Defect

Surface Distress Manifestations and Locations

Causes/

Mechanisms

Time of Appearance

Prevention of Reduction

Due to Physical Mechanisms

Freezing and Thawing Deterioration of Hardened Cement Pasts

Scaling of map-cracking, generally initiating near joints or cracks; possible internal disruption of concrete matrix

Deterioration of saturated cement paste due to repeated cycles of freezing and thawing.

1-5 years

Addition of air-entraining agent to establish protective air-void system.

Deicer Scaling and Deterioration

Scaling or crazing of the slab surface

Deicing chemicals can amplify deterioration due to freezing and thawing and may interact chemically with cement hydration products.

1-5 years

Limiting water-cement ratio to no more than 0.45, and providing a minimum 30 day drying period after curing before allowing the use of deicers.

Deterioration of Aggregate due to Freezing and Thawing

Cracking parallel to joints and cracks and later spalling; may be accompanied by surface staining.

Freezing and thawing if susceptible coarse aggregated results in fracturing or excessive dilation of aggregate.

10-15 years

Use of non-susceptible aggregates of reduction in maximum coarse aggregate size.

Due to Chemical Mechanisms

Alkali-Carbonate Reactivity (ACR)

Map cracking (rarely more that 50 mm deep) over entire slab area and accompanying pressure-related distresses (spalling, blowups)

Reaction between alkalis in cement and reactive silica in aggregate, resulting in an expansive gel and the degradation of the aggregate particle.

5-15 years

Use of on-susceptible aggregates, addition of pozzolans, limiting of alkalies in cement, minimizing of exposure to moisture, addition of lithium salts.

Alkali-Carbonate Reactivity (ACR)

Map cracking over entire slab area and accompanying pressure-related distresses (spalling, blowups)

Expansive reaction between alkalis in cement and carbonated in certain aggregates containing clay fractions

5-15 years

Limiting alkalis in cement, avoiding susceptible aggregates, or blending susceptible aggregates with non-reactive aggregate.

External Sulfate Attack

Fine cracking near joints and slab edges or map cracking over entire slab area

Expansive formation of ettringite that occurs when external sources of sulfate (e.g., groundwater, deicing chemicals) react with chemically active aluminates in cement or fly ash

1-5 years

Minimizing tricalcium aluminate content in cement or using blended cements, class F fly ash, or ground granulated blast-furnace slag (GGBFS)

Internal Sulfate Attack

Fine cracking near joints and slab edges or map cracking over entire slab area.

Formation of ettringite from internal sources of sulfate that results in either expansive disruption on the paste phase or fills available air voids.

1-5 years

Minimizing tricalcium aluminate content in cement, using low sulfate cement, eliminating source of slowly soluble sulfate, and avoiding high curing temperatures.

Corrosion of Embedded Steel

Spalling, cracking, and deterioration at ateas above or surrounding embedded steel.

Chloride ions penetrate concrete and corrode embedded steel

3-10 tears

Reducing the permeability of the concrete, providing adequate concrete cover and coating steel.


Evaluation of Pavement Shoulders by Khalel Ksaibati and Israel Crowe (Department of Civil Engineering, University of Wyoming, Laramie, Wyoming 82071-3295; ph.307-766-4253; http://www.eng.uwyo.edu/ce.html )(May 1999) [TE212.5.k73]

 

Highlights

  • shoulder widths vary depending on traffic volumes, terrain, and the cost of added width to the roadway section
  • significant reductions in accidents can be expected when shoulder widths are increased or if shoulders are added
  • on roadways with very low traffic volumes increasing the shoulder width results in an insignificant reduction of accidents
  • wider shoulders result in a slight reduction of vertical stresses to the pavement

Pavement shoulder widths are highly variable in rural roadways. Some rural highway sections are even constructed without any pavement shoulders. Pavement shoulders generally are provided to improve the safety characteristics of roadways. They also help in increasing roadway capacity. One theory states that shoulders may help increase the service life of pavements by reducing stresses due to loadings.

Shoulder width is the distance from the edge of the traveled way to the edge of the roadway. Shoulders are used to accommodate stopped vehicles for emergency use and are commonly used by pedestrians and bicyclists. Shoulder widths vary depending on traffic volumes, terrain, and the cost of added width to the roadway section. The materials used to construct shoulders are variable, and include concrete, asphalt, grass, gravel, and bituminous surface treatments. This study examined only paved shoulders, including asphalt and concrete.

The increased width to the roadway that shoulders offer helps to improve the safety of that roadway section. The extra space provides a place in case of emergencies, such as a flat tire. This additional roadway width also helps motorists to avoid conflicts. It also helps to accommodate driver errors. Drivers will have a little more time to react and compensate before they go off the road. Improving safety is a major advantage of pavement shoulders.

Some additional advantaged of shoulders are: increased sight distance in cut sections, improved highway capacity and added lateral clearance for signs and guardrail. Storm water can be discharged farther from the traveled way. The use of shoulders has many advantages; however, there are some disadvantages. These disadvantages include: additional construction cost and improper use by motorists, such as, using the shoulder as an additional driving lane.

The main objectives of this study were to examine the effect of pavement shoulders on the safety and structural strength of highways. This was performed by collecting data on representative highway sections from throughout Wyoming for a five-year period. A statistical and structural analysis were performed on the data.

It was determined that significant reductions in accidents can be expected when shoulder widths were increased or if shoulders were added to a roadway. Adding 0.6 M (2 feet) of shoulder width to a section with no shoulders has the most effect in reducing accident numbers. For each increment of 0.6 M (2 feet) of increased width thereafter, accident numbers will decrease, but not as significantly. These findings are consistent with similar studies performed at the national level.

Stresses under the load were examined to determine if there is a reduction in stresses with the added width of shoulders. This analysis indicated that shoulder width would result in a slight reduction of vertical stresses.

Effectiveness of adding pavement shoulders also was examined. Adding shoulders or increasing shoulder widths on roadways with relatively high traffic volumes reduced accident costs significantly. However, on roadways with very low traffic volumes it was determined that increasing the shoulder width would result in insignificant reduction of accident numbers.

Recommendations

·         Pavement shoulders should be implemented on roadways with high volumes. These shoulders will help in significantly reducing the number of accidents.

·         Wide shoulders are not effective on low volume roadways. However, the first 0.6 M (2 feet) of shoulder widening should be considered since it is quite effective in reducing accident numbers.


"Longevity of Diamond-Ground Concrete Pavements" by Shreenath Rao; et al. in Transportation Research Record 1684 (Transportation Research Board, 2101 Constitution Ave., NW, Washington DC 20418; ph. 202-334-2934; http://www/nas.edu/trb ) (1999) [TE7.H5#1684]

 

Highlights

  • grinding…
  • costs substantially less that an overlay
  • can be accomplished during off-peak hours with short lane closures
  • can be performed without having to close adjacent lanes
  • the smoothness that can be achieved through diamond grinding is comparable to that of a new pavement or an AC overlay
  • diamond-ground surface texture can lead to significant improvement in safety
  • if the existing pavement is sound, it may be reground numerous times to greatly extend its service life
  • the average age at failure of diamond-ground sections is greater than 32 years

Diamond Grinding is a concrete pavement restoration (CPR) technique that provides a smooth riding surface with desirable friction characteristics on concrete pavements. Diamond grinding can offer numerous advantages over other rehabilitation alternatives. Diamond grinding costs substantially less that an overlay, and can be accomplished during off-peak hours with short lane closures, and can be performed without having to close adjacent lanes. Also, grinding of one traffic lane does not require grinding of the adjacent lane, which may have perfectly acceptable surface characteristics. For concrete pavements in good structural condition, diamond grinding can be a highly effective and economical rehabilitation alternative.

The history of continuous diamond grinding for pavement restoration dates to 1965, when the technique was first used on a 19-year old section of the San Bernadino Freeway (I-10) in California to eliminate excessive faulting. Diamond grinding was used as the final step in the CPR program to provide a smooth riding surface. Diamond grinding since has become a major element of PCC restoration projects; however, very little valid documentation of the performance of diamond-ground pavements exists. The objective of this study was to provide the answers to frequently asked questions about diamond grinding, including the following:

·         What is the immediate impact of diamond grinding on pavement performance?

·         How long can diamond-ground surfaced provide acceptable ride quality?

·         How long can diamond-ground surfaces provide acceptable surface texture?

·         When is diamond grinding feasible and effective?

·         Can diamond grinding be used more than once on a pavement?

·         Are there any adverse effects of diamond grinding?

This objective was accomplished by conducting a comprehensive review of existing information on diamond grinding, gathering performance data, analyzing the collected data, and documenting the findings.

The results of this study show that CPR with diamond grinding is an effective means of extending the service life of concrete pavements. The immediate effect of diamond grinding is a smooth pavement surface with a desirable surface texture. The level of smoothness that can be achieved through diamond grinding is comparable to that of a new pavement or an AC overlay. Another important benefit of diamond grinding is a significant increase in surface texture and corresponding improvements in skid resistance. Studies have shown that diamond-ground surface texture can lead to significant improvement in safety, in terms of reduced accident rates.

Long term effectiveness of diamond-ground pavement depends on numerous factors, but the most significant factors are the condition of the existing pavement structure and the level of CPR applied. If the existing pavement is structurally sound, the pavement section may be reground numerous times to greatly extend its service life.

The field performance of diamond-ground sections is excellent. CPR with diamond grinding was effective in providing significant extension in service life at numerous projects. The average age at failure of diamond-ground sections is greater than 32 years, with many sections surviving 40 or more years. The results of service life, faulting, and texture analyses showed that a diamond-ground surface may be expected to provide about 10 years of service, at which time the pavement may be reground to provide further extension of service life. Cracking analysis showed that a pavement slab could be reground up to 3 or 4 times without compromising fatigue life. No evidence of any deleterious effects of diamond grinding was observed at any of the field sites.


Measuring, Achieving, and Promoting Smoothness of Virginia’s Asphalt Overlay by Kevin McGhee (Virginia Transportation Research Council, 530 Edgemont Rd., Charlottesville, VA 22903; ph. 804-293-1900; http://www.vdot.state.va.us/vtrc ) (April 1999) [TD100:VA99-19]

 

Highlights

  • only three variables significantly influence the achievable smoothness of an overlay:
  • the roadway functional classification
  • the ride quality of the original (underlying) pavement
  • whether the overlay was subject to the provision for smoothness
  • variables that were expected to affect achievable smoothness, but did not:
  • surface mix type
  • additional structural layers
  • milling
  • performing the work at night

Of the variables evaluated in this study, only three influence, with any practical significance, the achievable smoothness of an overlay: the roadway functional classification, the ride quality of the original (underlying) pavement, and whether the overlay was subject to the provision for smoothness. A fouth variable, the thickness of the new surface, showed some indication of affecting the ride quality. Unfortunately, there were too few examples of surfaces exceeding 40mm of thickness to draw wholesale conclusions.

1.      Functional classification. Overlays placed on interstate classification highways are generally smoother and subject to less variability than those placed on the primary systems.

2.      Original Surface Ride Quality. The achievable smoothness of a new surface is strongly associated with the ride quality of the original, underlying surface.

3.      Application of smoothness provision. The provision for smoothness was found to be most effective when applied to overlays placed over a good riding interstate pavement, good riding divided primary pavement, and fair riding divided primary pavement.

For several of the investigated variables, the lack of a measurable influence on ride quality is notable. Those variables that were expected to affect achievable smoothness, but did not, include surface mix type, additional structural layers, milling, and the requirement to perform the work at night.

1.      Surface mix type. The evaluation of mix type was limited to one family of mixtures, the SM-2 series. Within that family, no consistent trends associated with ride quality were identified.

2.      Additional Structural Layers. The analysis of the influence of additional layers on final surface smoothness returned no statistically significant results. There was little positive response, in terms of achieved overlay smoothness, associated with an added intermediate base layer. On the contrary, for two categories of resurfacing, the added structural layer actually resulted in higher average roughness.

3.      Milling. Milling was more notably associated with a higher average roughness (overlays of poor riding divided primaries). Overall, the results were mixed to inconclusive.

4.      Night paving. Perhaps the lack of a negative influence associated with paving at night was the most unexpected finding. Statewide, the necessity to pave at night had almost no measurable affect on achieved smoothness. For the one exception, resurfacing of fair riding divided primaries, the analysis suggested an overall improvement when the work was done at night.

Recommendations

·         Do not use high-speed profilers in highly urban areas, particularly where projects involve multiple signalized intersections. In these situations, the profiler operator can have difficulty negotiating the signal lights, not to mention the slower moving, higher volumes of traffic that generally accompanies them.

·         Do not use full size (and weight) profilers for monitoring new construction, especially for rigid pavements. Interim testing on partially completed surfaces can be difficult to impossible. Depending on the construction site, it can be very dangerous. By the time an agency can assess the rideability of an ongoing paving operation, it may be too late for a contractor to adjust and correct any problems.

·         Consider eliminating the "ending" exemptions on the smoothness special provision for maintenance. In fairness to the contractor, the specification should appropriately excuse contractors from responsibility for things he or she cannot control. It is reasonable, for example, to allow an exemption to a contractor for that portion of the overlay just past an exiting bridge approach. On the other hand, a good argument for excluding the last pavement joint from a smoothness tolerance is less obvious. Similarly, removing the exemption from joints leading up to the bridge approaches should also be considered. In either case, the contractor is given an opportunity to address ride quality in the surface leading up to that feature.

·         Use "roughness profiles" to address intra-project variability. An advantage to adopting roughness profiles is that the specification language would remain essentially unchanged. A base-length of 16m (52.8 ft.), which is used by the current bump special provision, is probably suitable. The improvement would be that the effect of bumps, of locally rough spots, would no longer be washed out across two adjacent 16m intervals. Any major surface flaw 16m or less in length would eventually manifest itself completely in a single MRI value. In effect, the specification has been tightened significantly with a very minor change in wording, if any.

·         Do not use conventional mill and replace to address smoothness issues. Regardless of the mechanism, milling appears to fortify the relationship between before and after overlay ride quality. If the original surface is fairly smooth, this may be desirable. If not, then the engineer may wish to investigate using something other than the traditional constant-depth milling or mill and replace.


Rest Area Forum: Summary of Proceedings by Patricia Hamilton (Turner Fairbank Highway Research Center, 6300 Georgetown Pike, McLean, VA 22101-2296; http://www.tfhrc.gov) (Dec 1999) [TD2.30:00-3-034]

 

Highlights

·         recommendations:

  • improve safety and security
  • support privately owned truckstops
  • use alternative parking sites
  • improve provision/location of public rest areas and privately owned truckstops
  • improve financial support
  • eliminate and enforce time limits
  • increase driver education and information

Recommendations

Improve safety and security. Recommendations included placing law enforcement substations at public rest areas and increasing police patrols at both public rest areas and privately owned truckstops. Several groups promoted a standard rating system for privately owned truckstops that would help drivers determine if a facility was safe and secure. They also encouraged states and the private sector to redesign landscaping and lighting at public rest areas to discourage crime. Groups proposed initiating a fast and efficient method that would allow drivers to report crimes and still maintain delivery deadlines.

Support Privately Owned Truckstops. To encourage private enterprise, the groups suggested providing low-interest loans, public/private partnerships, tax incentives, and signage on highways. Furthermore, they suggested using local law enforcement to respond to crime reports at privately owned truckstops. The groups also thought that efforts should be supported to address public resistance to truckstops/rest area expansion and construction (e.g., diesel emissions, noise, and citizen opposition).

Use Alternative Parking Sites. Because of immediate parking concerns, the groups recommended that short-term alternatives be investigated. These included the use of right of way at interchanges, park-and-ride lots, state fairgrounds, stadiums, farmer’s markets, and receiving and shipping facilities. Some recommended that parking be allowed at the designated weigh stations and government facilities (e.g., closed military bases and airports).

Improve Provision/Location of Public Rest Areas and Privately Owned Truckstops. Groups recommended that all states adopt uniform spacing standards between parking areas (e.g., 1-hour driving time). They recommended that shippers and receivers be encouraged to provide parking, especially in urban areas. Finally, groups recommended that closed public rest areas be reopened and additional parking be provided at those rest areas that already exist.

Improve Financial Support. To promote financial support, groups recommended raising the priority level of public rest area construction, modernization, and expansion by making rest areas a safety-related issue. Several groups recommended that the federal government allow states to use federal funds for public rest area maintenance. They also recommended that the use of federal, state, and local discretionary funds be explored to support public rest area construction, modification, and maintenance.

Eliminate and Enforce Time Limits. Some groups suggested eliminating time limits entirely, or at least eliminating those time limits that specify less that 8 hours for legally parked commercial motor vehicles at public rest areas. Others felt that police should enforce time limits, as space turnover is needed to accommodate the number of users. However, everyone was in agreement that if a driver was sleeping, he should be allowed to sleep and then be asked to make room for others.

Increase Driver Education and Information. All groups concurred that the results of current fatigue studies should be targeted to receivers, shippers, carriers, and insurance companies as well as drivers. The groups also made several recommendations about providing drivers with information about the location and availability of public rest areas. These recommendations included providing signage on corridors, intelligent transportation systems technology to deliver real-time parking information, and uniform logo signage about commercial vehicle parking availability. The recommendations also included providing a list or a logo indicating public rest areas and privately owned truckstops on state maps and information pamphlets, and a radio channel or cellular telephone number to communicate public rest area or privately owned truckstop information.


"Analysis of Factors Contributing to ‘Walking Along Roadway’ Crashes" by Patrick McMahon, et al. in Transportation Research Record 1674 (Transportation Research Board, 2101 Constitution Ave, NW, Washington, DC 20418; ph. 202-334-2934; http://www.nas.edu/trb )(1999) [TE7.H5#1674]

 

Highlights

  • absence of sidewalks, higher traffic volume, higher vehicle speed, and smaller width of unpaved shoulder increase the likelihood of a walking-along-roadway pedestrian crash
  • neighborhood characteristics that increase the likelihood of a walking-along-roadway crash include high percentages of single parents, large amounts of housing built before 1980, few households composed of families, and high levels of unemployment

The goal of a transportation system is to provide safe and efficient mobility and access to a wide variety of travelers with diverse needs and for different modes of travel. Walking is the most basic form of transportation, and it is important for transportation officials to provide facilities that enhance safe movement for pedestrians along roads and streets. An individual’s transportation needs, and his or her ability to achieve them, are likely to vary not only from the physical roadway environment, but also from socioeconomic situations and proximity to potential activities that attract pedestrian traffic. Neighborhoods have their own specific patterns of transportation, and travelers within those neighborhoods may be subject to different risks than are encountered in other areas.

The purpose of this paper is to identify the types of, and reasons for, risks to pedestrians who are walking along a roadway. Factors examined in this study include both roadway factors and neighborhood factors. The sampling methodology matches crash sites where pedestrians were struck walking along a roadway to comparison sites of similar zoning, parcel size, and development amount, much like the matching done in a case-control study. Such roadway factors as vehicle volume, pedestrian volume, presence of a sidewalk, shoulder width, and type of roadside are included in the analysis.

Census data from the U.S. Census block group in which each site was located were attributed to that crash site in order to analyze the impact of socioeconomic factors (e.g., unemployment level, age of housing, and number of parents in the household).

Roadway characteristics such as the absence of sidewalks, higher traffic volume, higher vehicle speed, and smaller width of unpaved shoulder increase the likelihood that a walking-along-roadway pedestrian crash will occur. By controlling for these factors, this study also found that neighborhood factors influence the likelihood of a site being a crash site. Specifically, neighborhood characteristics that increase the likelihood of a walking-along-roadway crash include high percentages of single parents, large amounts of older housing (i.e., housing built before 1980), few households composed of families, and high levels of unemployment. It is believed that neighborhood factors capture the extent and type of exposure (i.e., safe of unsafe walking behavior) that takes place in conjunction with these factors.

These findings suggest that certain types of neighborhoods contain factors that increase the risk of pedestrians being involved in walking-along-roadway crashes. Specifically, sidewalks appear to be the most appropriate treatment on neighborhood streets, while wide, unpaved shoulders may be more suitable in more rural areas. Further, neighborhoods with larger numbers of single parents, older housing stock, greater dependency on public transit, fewer families, and higher unemployment might deserve added consideration for improvements in pedestrian facilities. These would provide a safer place for pedestrians to walk than in the travel lane or on a paved shoulder by physically separating the individual further from the traffic while walking adjacent to the street or roadway.

As part of a larger study for the Federal Highway Administration, the results of this study are being used to develop improved national priorities and guidelines for the installation of sidewalks, walkways, and shoulders. Providing such facilities for pedestrians will not only reduce pedestrian crashes, but also improve pedestrian access. Such facilities also encourage more walking, which improves health and longevity for those who walk regularly. The Institute of Transportation Engineers gives the design guidelines for sidewalks in its 1998 report titled Design and Safety of Pedestrian Facilities.

It also should be mentioned that the analyses in this study were limited to all walking-along-roadway crashes in Wake County, North Carolina, in a four year period (1992-1996). While such a study certainly could be conducted in other areas of the country, the results here are consistent with findings of previous research on roadway and neighborhood issues in terms of factors that affect pedestrian crash experience.

Beyond the variables tested here, it is expected that other variables, such as alcohol and drug usage, crime rate, and other indications of risk taking, could be incorporated successfully into this type of model to further explain behaviors that increase risk of exposure to this type of crash. Even more appropriate would be more qualitative research involving the interviewing of neighborhood residents and those familiar with a variety of neighborhoods to determine some of the root causes for the current levels of risk and what they believe to be locally appropriate countermeasures.


Automatic Detection of Driver Fatigue, phase III by Sarbjit Singh Kaur, et al. (University of Minnesota, Department of Computer Science, Artificial Intelligence Laboratory, 4-192 EE/CS Bldg. – 200 Union Street, SE, Minneapolis, MN 55455-0159; ph. 612-625-8544; http://www.umn.edu ) (Jun 1999) [TD100:MN99-30]

 

Highlights

  • This report is organized as follows:
  • the system operation
  • the experimental setup
  • the eye tracker
  • results and future work are discussed
  • conclusions

A large number of automobile accidents are caused due to driver fatigue. Sleep deprivation is becoming a more common problem for car drivers in a society in which people seem not to have enough time to perform all the activities they need to carry out in a daily basis. Reducing the number of accidents related to driver fatigue would save the society a significant amount of money and personal suffering. By monitoring the driver’s symptoms, we can determine driver fatigue early enough as to take any preventive course to avoid an accident due to lack of awareness.

There are many indicators of oncoming fatigue, some of which are possible to detect by using a camera. Two of the most notorious of these symptoms that feasible to detect are micro-sleeps (short periods, 2-3 seconds, in which the driver loses consciousness) and the forward bouncing movement of the driver’s head.

The input to the system is a continuous sequence of images fed from a video camera. From this sequence, the system can analyze the eyes in each image, as well as compare the eyes between images. The analysis of facial images is a popular research area with applications such as face recognition, virtual tools and handicap aids, human identification and database retrieval. There are also many real-time systems being developed in order to track face features.

For this study of fatigue in the form of micro-sleeps, the authors extracted and tracked the eye locations throughout the entire video sequence. This is a valuable information in order to detect micro-sleep symptoms. Th authors achieved this by dividing the problem into the following phases:

1.      Location of the eyes (in the first frame),

2.      Tracking the eyes in the subsequent frames,

3.      Detection of failure in tracking.

Locating the eyes at the first frame is the most computationally expensive phase of the system. In this phase, the system has no previous information about the eye’s location in the image. The system has to find the area of the image that will be used in the subsequent frames in order to track the eyes. During the tracking phase, the search space is reduced as the system has an approximate knowledge of the eye’s position in the previous frame. This tracking can be done at a relatively low computational effort. In order to detect failure in tracking, general constraints such as the distance between the eyes and the horizontal alignment of the two eyes can be used. The eyes should be relocated after a certain period, even though no failure has been detected, to periodically make sure that the correct figure is being tracked.

For detection of fatigue in the form of head-bouncing movements the authors present a real-time face profile tracking system. They added a second camera to the system, which detects fatigue in the form of backward or forward head bouncing movements. As the face tracker, it uses skin color based on approach to locate the profile and it performs blob statistics analysis to determine the inclination.


"Can We Make Red-Light Runners Stop? Red-Light Photo Enforcement in San Francisco, California" by Jack Fleck and Bridget Smith in Transportation Research Record 1693 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb )(1999)[TE7.H5#1693]

 

Highlights

  • experience shows that engineering solutions should be considered first
  • photo enforcement has shown that it can increase public safety in a revenue neutral manner
  • it is better when working with community associations to give them a list of intersections and ask for comments than ask for their candidate intersections
  • people are less likely to tie up the court contesting when they can see the photographs

Debate continues nationwide on whether it is more cost-effective to use cameras versus police officers in the field. Given the low issuance rate and high cost of automated enforcement, this is a valid concern. However, red-light photo enforcement has the advantage of operating 24 hours per day. It also may have a spillover effect, most likely because drivers cannot always keep track of the monitored locations. It also is likely that the cost of photo enforcement in the United States will drop as more cities start programs, technology develops, and the law evolves.

Cameras clearly are not a replacement for police officers. San Francisco’s expanded program is considering 36 intersections, but it has more than 1000 signalized intersections. Obviously, the police are always going to be a critical part of enforcing red-light violations. In addition, police officers enforce many laws besides red-light running. Ideally, an automated enforcement program is one component of a broad-based traffic safety program including engineering, education, and enforcement.

Fortunately, the increased fine established in California provides the resources to support such a program. The bottom line is that photo enforcement, in combination with education and stiff police enforcement, has shown that it can increase public safety in a revenue neutral manner.

In the pilot program, project staff selected intersections based on five criteria:

It is also important to consider several other factors. Construction difficulties such as inadequate conduit space, sub-sidewalk basements (typical in San Francisco), and other obstacles to installing detector loops or conduits can greatly increase the cost of a program. Field observations of red-light violators at prospective intersections are useful before selecting locations, especially to determine which intersection approach is best for photo enforcement. Time and effort can be saved when working with community associations by giving them a list of priority intersections and asking for their comments, rather than asking for their list of candidate intersections for photo enforcement.

Of the various considerations and criteria, the best indicator of red-light running is the number of collisions caused by red-light violators. Experience, however, shows that engineering solutions should be considered first. The intersection near San Francisco State University where the 1994 collision took place that inspired the program was one of the first locations equipped for photo enforcement. After traffic engineers modified the signal progression, red-light running virtually stopped at this location. Preliminary data from other pilot intersections suggest that engineering solutions often can reduce red-light violations significantly. Several pilot locations are undergoing engineering improvements, such as increasing the yellow-light interval and introducing mast arms. The presence of photo-enforcement equipment at these intersections will allow San Francisco’s traffic engineers to learn more about the effectiveness of various engineering improvements on making red-light runners stop. Future locations with the potential for such engineering solutions are now being considered for the program expansion.

Photographs on Citations

During the first year of the pilot program, EDS printed photographs on each citation issued, whereas USPT provided prints for public viewing. San Francisco’s staff concluded that there are substantial benefits to printing the photograph on the citation. Registered owners do not have to visit the court to view the photographs. People are less likely to tie up the court contesting when they can see the photographs up front. San Francisco’s program now provides four photographs on each citation: one of the vehicle entering the intersection, one of the vehicle clearing the intersection, a close-up of the driver’s face, and a close up of the license plate.

Overall, San Francisco’s experience has been enlightening and gratifying. San Francisco’s public, media, and elected officials all have supported the program and worked hard to make it a success. The drop in red-light runners and the drop in collisions justify continuing and expanding the program. San Francisco’s pilot red-light photo-enforcement program has shown that we can make red-light runners stop. Red-light photo enforcement is one tool to make this happen.


"Driving and Using Mobile Phones: Impacts on Road Accidents" by P.A. Koushki, et al. in Transportation Research Record 1694 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb )(1999)[TE7.H5#1694]

 

Highlights

  • mobile phones are most heavily used by young adults in Kuwait, the population with the least driving experience
  • the risk involved in the use of mobile phones while driving was similar to the hazard associated with driving with a blood alcohol level at the legal limit
  • individuals who were on the mobile phone once during an average urban trip experienced three times as many accidents
  • the paper strongly recommends the banning of driver mobile phone use while the driver’s vehicle is in motion

Many public officials share the belief that driver use of mobile phones will have a significant adverse impact on road safety. A recent survey of a sample population in Kuwait shows that 80% of Kuwaiti adults own mobile phones and that an additional 3% rent automobile phones. Seventy-six percent of those who owned a mobile phone were under 30 years of age, and 57% were male. These statistics reflect the prestige (fashionableness) of mobile phones among young adults in Kuwait, the population with the least driving experience.

Research on the effect of driver use of mobiles while in motion is extremely limited. In a recent study performed at the University of Toronto the accident records of 699 drivers who owned mobile phones were examined. It was found that those who used mobile phones while driving were four to five times as likely to get into a traffic accident as other drivers. In addition, the study found that mobile phones that allowed the hands to be free did not appear to be safer than hand-held phones, suggesting that it is the distraction (limitations in attention) from mobile phone use while driving instead of the dexterity problem that magnifies the hazard level. The study also concluded that the risk involved in the use of mobile phones while driving was similar to the hazard associated with driving with a blood alcohol level at the legal limit. The use of mobile phones while driving is banned in Israel, Brazil, and Australia.

In a study of road accidents in Tokyo, Japan, it was found that, in 1997, driver use of mobile phones was the cause of 2297 road accidents. More than 3000 individuals were injured in these accidents, and 25 people lost their lives. A total of 27.6% of the mishaps had occurred during the dialing process, and 16.4% occurred during conversations.

Conclusions

Within a rather short period of time since the introduction of mobile phones, nearly three fourths of all drivers in Kuwait own a mobile phone. These individuals use their mobile phones an average of 1.5 times during an urban trip and spend in excess of US$50 per month on mobile phone bills. On the average, over the last 2.5 years more than one in five of all road accidents in which a driver in the study sample was involved was related to mobile phone use. Seven of 100 of such road accidents caused injuries, and 8 in 1000 resulted in fatalities

Of importance, however, was the significant contribution to the occurrence of road accidents made by a single use of a mobile phone while driving. The study revealed that individuals in the study who were on the mobile phone once during an average urban trip experienced three times as many accidents involving property damage and four times as many injurious traffic accidents as those who never used their mobile phones. This finding reflects the significant impact of distraction resulting from a single use of a mobile phone while driving.

The study findings also clearly indicated that regardless of age, gender, marital status, education, and family life cycle, the number of property-damage-only, injurious, and fatal road accidents increased with increasing frequency of mobile phone usage during a trip. There is no doubt that the rapidly growing use of mobile phones by drivers while their vehicle is in motion has added a new dimension to the inherent complexity of the driving task, further compromising road safety. This adverse impact is all the more significant in a driving environment such as Kuwait’s, which is generally characterized by an inexperienced, under trained, and undisciplined driver population operating in a relaxed law enforcement environment. The danger of mobile phone use while driving is rather obvious. Waiting for results of a study with even one more sample means another unnecessary loss of life and limb. The paper strongly recommends the banning of driver mobile phone use while the driver’s vehicle is in motion.


"Effects of Heavy Vehicle Mechanical Condition on Road Safety in Quebec" by Michel Gore, et al. in Transportation Research Record 1686 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb )(1999) [TE7.H5#1686]

 

Highlights

  • 13% of accidents involving heavy vehicles result from non-complying mechanical components
  • more that 50% of major defects affect the braking system components
  • heavy vehicles with major non-complying components have a propensity to be involved in accidents that is five times higher

Despite the small size of samples, the findings from this study give a relatively clear understanding of heavy-vehicle involvement in traffic accidents and of the effect of mechanical conditions on road safety. In brief, the study shows that approximately 13% of accidents involving heavy vehicles result from non-complying mechanical components on those vehicles and that the braking system is the most frequent cause of accidents involving mechanical defects. Furthermore, the study shows that disregarding accident causes, heavy vehicles with major non-complying components have a propensity to be involved in accidents that is five times higher than that of complying vehicles.

This study also has provided an idea of the inspection program’s effect on heavy-vehicle mechanical condition. Considering the high correlation between mechanical condition and vehicle age (based on model year), the application of the program needs to be tightened, especially for heavy vehicles that are more than 12 years old. A more extensive analysis of the nature of observed defects has shown that more that 50% of major defects affect the braking system components. The inspection program’s presumed effectiveness in detecting defects in that system is very high, so its quick deterioration cannot be explained entirely by deficiencies in the application of the program.

Based on these findings, it is recommended that:

·         The propensity index for involvement in accidents for heavy vehicles with serious defects alone justifies maintaining and even intensifying the present inspection program. Rigorous inspections conducted within the framework of the inspection program should be ensured by training mechanics better and by controlling the quality of inspection services

·         The high rate of major defects is particularly inflated by braking system defects (53%). Reducing defects in this system would improve heavy-vehicle mechanical condition noticeably. For this reason, preventative maintenance of this system every 300 hours of service or 12,000 km is recommended. Furthermore, efforts to develop better performing brake systems should be encouraged.

·         Mechanical inspection should rely on well-adapted equipment rather than on mere visual examination to carry out effective and rapid inspections of braking systems.

·         The inspection program’s presumed effectiveness in detecting defects varies from one mechanical system to another. A quality control process among mechanics for ensuring rigorous and uniform inspections should be implemented or encouraged.

·         Besides the inspection program, frequent roadside inspections should help keep non-complying vehicles off the roads.

·         Pre-trip inspections appear to be the ideal complement of the inspection program in preventing accidents caused by mechanical defects. Drivers should be better trained in how to make an inspection and should use visual indicators to verify the adjustment of brake-cylinder push rods.

·         Results from this study indicate that mechanical condition is responsible for between 9.6% and 20.2% of accidents involving heavy vehicles. More accident surveys and other analyses are needed to reduce sampling errors and validate statistically some findings from this study.

·         Some variables that help evaluate heavy-vehicle exposure to accident risks should be collected more systematically.

·         Knowing the condition of vehicles from the moment they enter the garage for their inspections would help in evaluating the inspection program’s ability to detect mechanical defects in the various systems. All mechanical inspectors should be required to record inspection program results from the moment vehicles come into the garage, not just when they leave.

·         Adding rear and lateral under-ride guard rails on the chassis of heavy vehicles could have saved a few lives or noticeably reduced the seriousness of injuries. There is thus a need to evaluate the cost-benefit ratio of installing such bars because they are not yet mandated in Canada.

·         Most other road users seem to have a wrong perception of heavy-vehicle driver’s field of view. A well-targeted information campaign on the problem undoubtedly would help prevent some accidents.

·         Heavy-vehicle drivers must be trained in the proper ways of securing their loads. This could help prevent almost 2% of accidents involving heavy vehicles.


"Effects of Weather-Controlled Variable Speed Limits and Warning Signs on Driver Behavior" by Pirkko Rama in Transportation Research Record 1689 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb )(1999) [TE7.H5#1689]

 

Highlights

  • weather-controlled system decreased both the mean speed and the standard deviation of speeds
  • the average speed reduction was 3.4 km/h
  • the system proved to be more effective when the adverse weather and road conditions were not easy to detect
  • the speed reductions were not sufficient to make the VMS system economical on low volume roads

                The purpose of this study was to investigate the effects on driver behavior of variable speed limits and signs for slippery road conditions. The main results indicated that the weather-controlled system decreased both the mean speed and the standard deviation of speeds. On the control highway section where there were no variable message signs (VMSs) the mean speed was also decreased during adverse weather and road conditions, but less, and the variance of speeds increased. The average speed reduction was 3.4 km/h in winter.

Adverse weather and road conditions in winter, for example, "black ice," are sometimes difficult to detect as hazardous by drivers. This has been one of the motivations to build up weather-controlled sign systems because one might expect the systems to be most effective in these situations. In order to examine this effect, the data were divided into two parts according to rain intensity. The results showed that when there was no considerable rain, the mean speed decreased more (1.9 km/h) than it did on average. Specifically, the effect on the experimental road remained the same, but the average effect of the weather was smaller on the control road. Hence, the system proved to be more effective when the adverse weather and road conditions were not easy to detect.

The combined effects of the lowered speed limit and the sign for slippery road were smaller than expected. However, in these situations the effect of the weather as such on speeds was substantial. Evidently, the adverse weather and road conditions were very obvious, and as a result, the effects of the system were less substantial.

The analysis of the speed distribution showed that the speed patterns were different in winter and in summer. In winter, when weather and road conditions became adverse, the speed variance on the control road increased. Specifically, the 15th percentile speeds decreased substantially more than the 85th percentile speeds. This finding might indicate that many drivers tended to drive according to the speed limits (i.e., speed limits are understood not only as the highest allowed speed limits, but also as speed recommendations). Under adverse weather and road conditions, some drivers on the control road lowered their driving speed when others continued to drive at a speed close to the maximum speed allowed. The use of variable speed limits on the experimental road prevented this increase of speed variance. In summer, the 85th percentile was decreased more than the mean speed. Conclusively, the weather-controlled system increased the homogeneity of driver behavior, which has a positive effect on traffic safety.

The effect of the weather-controlled system was estimated by subtracting the effect of weather and road conditions found on the control road from the combined effects of road and weather conditions and VMSs. Consequently, the estimated effect was directly dependent on the estimate of the weather effect. In general, the speed decreased considerably on the control road because of adverse weather and road conditions, in some cases even more than expected. For a number of reasons, it is likely that the error in the estimate is on the safe side; that is, the effects of the VMS system are underestimated.

First, in the current study, the mean speed on the control road was higher than the mean speed on the experimental road under good conditions. One reason for that might be that the variable signs look different compared with the fixed signs. An earlier study has shown that there is better compliance with variable speed limits shown on signs that use fiber-optic technology. In any case, one might assume that there was less potential to reduce speed on the experimental road when the speed level was lower than that of the control road.

Second, the rains come typically from the west in Finland. The control road was further (about 100km) toward the west. Because of the time definitions of the data (which were necessary to control some other factors), the control data showed more times when the rain had lasted longer (approximately 1 hour) than did the experimental data. Also, the proportion of heavy rain was greater in the control data than in the experimental data. This effect was examined using the data without the first hour of the experimental data. This treatment had no substantial effect on the results. However, the analysis according to rain intensity showed that when there was heavy rain, the speed decrease was more substantial on the control road than on the experimental road. This finding might imply that the rain had lasted longer and that there was more snow on the road. Under these conditions, the effect of the weather was substantial and decreased the estimate of the effects of the sign system.

The assessment of the system function showed that there is also some need to develop the system technically. Specifically, a more sophisticated system to recognize adverse weather and road conditions and low friction is needed.

In conclusion, the concept of weather-controlled speed limits and displays was successful. The weather-controlled VMS system contributed to safer driving during adverse road conditions by decreasing the mean speed and standard deviation of speeds. However, it was found that the speed reductions were not sufficient to make the VMS system economically profitable on this road, which had quite low traffic volumes.


"Impact of Passengers on Young Driver Safety" by Brian Aldridge, et al. in Transportation Research Record 1693 (Transportation Research Board, 2101 Constitution Ave NW, Washington, DC 20418; ph.202-334-2934; http://www.nas.edu/trb )(1999)[TE7.H5#1693]

 

Highlights

  • young drivers have the lowest propensity to cause accidents when travelling with adults and/or children
  • they have an increased propensity for causing accidents when travelling with peers
  • vehicle accident propensity for young drivers with peers increases with the number of people in the vehicle

Although most people agree that teenage drivers have a greater risk of accidents than their older counterparts do, the reason for this conclusion is disputable and is more complicated than purely age and experience. Many factors contribute to the risk-taking behavior of teenage drivers, including lifestyle, mood of driver, drug involvement, decision-making processes, and passengers in the vehicle. All of these factors bias the driver’s behavior in some fashion. Although previous research has been conducted to analyze the manner in which most of these factors affect teenage drivers, more research still is needed to better understand the influence of teenage passengers (and others) on the behavior of young drivers. This is particularly important as many states consider the implementation of graduated licensing programs that may include restrictions on who may be a passenger in a vehicle driven by a young driver. The background studies discussed here suggest that risk taking and vehicle occupants are factors in young driver accidents, which motivates the undertaking of the analysis in the paper that furthers the work on the impact of passenger type on young drivers causing accidents.

Conclusions

Through the use of the quasi-induced exposure method, it has been possible to correct the number of accidents caused by young drivers by an estimate of the relative mount of time they travel with different passenger groups. Passenger group was found to have a significant effect on young driver accident propensities. Young drivers have the lowest propensity to cause single- or two-vehicle accidents when travelling with adults and/or children. They have an increased propensity for causing single-vehicle accidents when travelling with peers. The relative accident involvement ratios for both single-vehicle and two-vehicle accidents for young drivers traveling alone were close to 1.0. The results suggest that risk taking is a factor (as opposed to only skill or experience) in young driver safety.

Seven variables were considered for possible interaction with passenger type: driver gender, total occupant gender, time of week, time of day, highway type, vehicle age, and safety restraint usage. Only four statistically significant results were found. All-male vehicle occupants including an adult-or-child passenger combination were found to have lower two-vehicle accident involvement, suggesting that male adult supervision is a strong positive influence for young male drivers. Single-vehicle accident propensity for young drivers with peers increases with the number of people in the vehicle. Young men have lower accident propensity than young women drivers when traveling with the adult-or-child group. Young drivers with adult/child passengers have higher single-vehicle accident propensities on four lane highways.

The findings reported here support Kentucky’s new graduated licensing program, which began in November 1996. Under the new program, 16-year-olds must now wait 90 days from receipt of a learner’s permit until they are eligible to take the required road test for an operator’s license. During this period, the young driver must be accompanied by an adult (at least 21 years of age). The findings in this report suggest that increased education and a prolonged period of adult supervision among this class of drivers will yield safer highways. A comparison can be made in the upcoming years (when new data become available) to determine if this is indeed the case.

 

Single-Vehicle Accident Involvement Ratios

Category

Subset

Solo

Peer

Adult/Child

Passenger Group

 

0.90

1.33

0.74

Gender

Male

Female

0.89

0.93

1.32

1.28

0.76

0.81

Passenger Gender

All male

All female

Mix

 

1.05

1.12

1.12

0.78

0.74

0.76

Number of Passengers

1

2

3+

 

1.08

1.28

1.36

0.68

0.54

0.55

Day of Week

Weekday

Weekend

0.91

0.89

1.32

1.31

0.77

0.69

Day or Night

Day

Night

0.95

0.91

1.23

1.22

0.68

1.07

Number of Lanes

2

4+

0.92

0.91

1.29

1.22

0.68

1.07

Vehicle Age

-1 to 3

4-10

10+

0.92

0.91

0.88

1.26

1.29

1.33

0.79

0.77

0.95

Safety Restraint Usage

Harness/lapbelt

Not in use

0.92

0.87

1.30

1.27

0.79

0.82


Investigation of the Uses of Mobile Phones While Driving by Alastair Cain and Mark Burris (Center for Urban Transportation Research, College of Engineering, University of South Florida, 4202 E. Fowler Ave, CVT100, Tampa, Fl. 33620; ph.813-974-3120; http://www.usf.edu )(Apr 1999)[TL152.3.C34]

 

Highlights

  • mobile phone use has an adverse effect on driving performance
  • people who used a mobile phone while driving were anywhere from 34% to 300% more likely to have an accident
  • with mobile phone use likely to continue to increase in the future, the safety of driving while using a mobile phone will become a very important issue

The number of mobile phone users in the U.S. has grown from 500,000 in 1985 to 63 million in 1998. This rapid growth has occurred largely without consideration of the mobile phone’s suitability for usage while driving. The objective of this report is to summarize existing information on the subject of mobile phone use while driving, in order to provide a concise summary of the issues for the public, researchers, and legislators alike. The report discusses the benefits of mobile phone usage while driving, such as driver safety and time use efficiency, and negative aspects such as its potential for driver distraction resulting in accidents.

The report contains information on the demographics of mobile phone use in the U.S., focusing on user demographics and frequency of usage while driving. Although once used primarily by high income business people, user demographics are now much more similar to the demographics of the U.S. population as a whole. Findings from literature on the subject of mobile phone use and driving performance are highly variable. In general, the literature shows that the effect of mobile phone use on driving is a complex issue with several influencing factors including the type of mobile phone used, the type of conversation undertaken, and the demographics of the user. In general, it was found that mobile phone use does have an adverse effect on driving performance, but the significance of the distraction is difficult to quantify. Reports found that people who used a mobile phone while driving were anywhere from 34% to 300% more likely to have an accident.

At present, only two states include specific "check boxes" on their accident investigation forms to identify mobile phone use as a factor in crashes. This report concludes that data collection on a national scale is the first, most important step to accurately evaluating the risk associated with mobile phone use. Several countries have already banned mobile phone use while driving, and legislation has been proposed in nine states in the U.S. At the time of this report (April 1999), no U.S. legislation on this issue had progressed to become law. There are numerous reasons for this, including the lack of data to support legislative action. Alternatively, laws may develop through civil court cases where mobile phone users, manufacturers, service providers, etc. are found liable for automobile accidents.

With mobile phone use likely to continue to increase in the future, the safety of driving while using a mobile phone will become a very important issue. Therefore, it is important to begin to collect better data on the risks associated with using a mobile phone while driving. In this manner, the need for legislation can be accurately measured, and, if legislation is needed, its extent, role, and effectiveness in saving lives can be better assessed.

Do you talk on the phone while driving?

 

Male

Female

Avg.

Most Trips

16%

5%

11%

About Half

10%

9%

9%

Less Than Half

17%

12%

15%

Very Few

49%

59%

54%

Never

7%

14%

11%

Source: NHTSA Motor Vehicle Occupant Survey

 

Phone Activity When Crash Occurred

Calling/

Operating

Receiving Calls

Talking

Other

23%

43%

17%

17%

Source: Traffic Planning Department, National Police Agency of Japan