Intelligent Speed Assistance on London Buses: A trial on two London bus routes

This report, produced by the Transport Research Laboratory (TRL) on behalf of Transport for London (TfL), gives the results of a trial of the use of Intelligent Speed Assistance (ISA) in London buses.

TfL carried out a trial of ISA technology on a small number of vehicles in its bus fleet to understand the potential role of this technology in promoting adherence to speed limits across the road network, and its impact on reducing killed and seriously injured (KSI) casualties.

The report provides an analysis of the impact of ISA devices fitted to vehicles serving two bus routes within London. Comparable measurements were taken both before and after the ISA equipment was fitted to address eight research questions.

The ISA system was generally found to limit speeds as anticipated, with occasional failures on downhill sections of road where the bus would temporarily exceed the speed limit under the influence of gravity. Compliance with the speed limit improved after buses were equipped with ISA; the percentage of time buses spent travelling above the speed limit reduced from a range of 14.9-17.8% to 1-3.3% in 20mph zones, and 0.5-3.3% to 0-1.1% in 30mph zones.