After graduating in Switzerland, Roger Waller was employed by the Swiss Locomotive Machine Works (SLM) at Winterthur. In 1982 he joined the South African Railways and worked as an assistant to Wardale during the latter stages of the tuning-up and testing work on The Red Devil. He returned to SLM in 1984 and was responsible for the development of the all-new Class H2/3 rack locomotives, eight of which had been built in 1992 and 1996 and are since in service in Switzerland (on the Brienz-Rothorn Bahn) and in Austria (on the Schafberg railway). These engines embody a number of advanced features, including light oil firing giving very low exhaust emissions and allowing one-man operation on the steep 1 in 4 mountain railways on which the locomotives are used. By comparison with the previous 1933 design, the new locomotives are 25% lighter and develop 36% more power, this resulting in 61% less fuel being consumed per passenger trip, with a top speed 56% higher. They are thus operationally equivalent to diesel locomotives yet retain the commercially important appeal of steam traction. These are probably the only steam locomotives worldwide that are relegating diesel to spare power.
On Lake Geneva, a diesel-electric paddle ship had even be re-converted to steam in 2000. In order to be competitive to diesel ships SS Montreux had been equipped with a fully automatic boiler and a remote control for the all-new steam engine, so that no additional staff is required compared to a diesel ship.
Following on the success of the new rack locomotives, Waller and his team at SLM extensively rebuilt ex-Deutsche Reichsbahn 52 Class 2-10-0 No. 8055, which incorporates some of the features of the rack tanks, such as light oil firing and ultra-thick thermal insulation. This rebuild was first tested in 1999 and after a period of inactivity in Germany (caused by regulatory authorities), the locomotive returned to Switzerland in 2003 under the ownership of DLM where it operates regularly on special services, most recently in conjunction with the Swiss project modern-steam-hauenstein.ch A new 4-8-4 tank locomotive for one-man operated push-pull trains has recently been proposed for this project.
In 2000 the steam group at SLM initiated a management buy-out. The new company, Dampflokomotiv- und Maschinenfabrik DLM AG , with Roger Waller as its President and CEO, concentrates mainly on modern, economic and environmentally friendly steam technology.
In Feb 2003 Waller presented a paper titled "Modern Steam - An Economic and Environmental Alternative to Diesel Traction" to the Institution of Mechanical Engineers Railway Division under the auspice of the "Sir Seymour Biscoe Tritton Lecture".
Most recently DLM is working on a revival of fireless locomotives. There is no doubt that modern fireless locomotives will be far superior to diesel shunting locomotives in terms of economy and ecology.