My father-in-law Dennis Robertson, who has died aged 92, was an engineer specialising in flow dynamics, who led the development of the modern traffic light system in the UK in the 1970s and 80s.
Dennis joined the Transport and Road Research Laboratory (now the Transport Research Laboratory) in Crowthorne, Berkshire, in the early 1970s where he began research into traffic flow management. This was a relatively new and increasingly important area of study as car ownership and congestion in British cities was increasing.
Dennis and his team found that the existing approach to traffic light phases, with fixed periods of green and red, was unsuitable and often problematic in British cities, causing avoidable congestion. Instead, using data captured from sensors embedded in roads ahead of traffic lights combined with developments in computing, the TRRL team developed an algorithm that would continually modify the traffic light phase length dependent on the traffic approaching and waiting at red lights.
This led to the development of the algorithmically controlled traffic light system Transyt (Traffic Network Study Tool) for which Dennis, in 1982, was awarded the Esso Energy award by the Royal Society for “significant contribution to energy saving”. Transyt was further refined so that it would consider input and feedback from other traffic lights in the same city, reacting to flow demand across the whole city system, and this led to an improved algorithm and system named Scoot (Split Cycle Offset Optimisation Technique).
Dennis travelled the world to present the Scoot approach and benefits, and the software is still used in more than 350 towns and cities across the globe. In 1987 Dennis was recognised for his work in the field of transport research with an honorary doctorate from the University of Waterloo in Ontario, Canada. In 2003, he was appointed OBE.
Dennis was born in south London, the son of Kenneth, a commercial traveller and builders’ merchant, and his wife, Lily (nee Birch). After leaving school and completing his national service in the RAF, he began work as an apprentice engineer at Napier engineers in Acton. During his apprenticeship, he studied for a University of London mechanical engineering degree at evening classes, graduating with a first. He moved to work for the British Aircraft Corporation, working on the TSR-2 reconnaissance and strike aircraft, primarily on the design of the cockpit instrumentation. Though the TSR-2 was eventually cancelled, Dennis remained proud of his work on the project.
After 20 years with the TRRL, Dennis retired in 1992, having reached the position of deputy director. He continued to have an active interest in traffic research, particularly the use of pay-per-mile traffic management.
He also began to play bridge and spent many hours computing. A keen photographer and videographer, he embraced digital photography, and also enjoyed life in the local community with the U3A, Rotary and Probus.
Dennis is survived by his second wife and their daughter, by a son from his first marriage, and by a stepson.
