In 2015, Transport for London (TfL) launched a trial of intelligent speed assistance (ISA) technology in London with the installation of ISA devices on all buses travelling on two of its major London bus routes (route 19 in central London and route 486 in south-east London).
The ISA devices used a digital speed limit map of London, developed by TfL, and GPS data to identify the prevailing speed limits throughout each vehicle’s journey. The device then limited acceleration of the bus beyond the posted speed limit.
Data collected before the trial indicated that speed compliance issues mostly took place during the late evening; on off-route sections of the journey (e.g. between the bus depot and the start/end of the bus journey); and on 20mph roads.
The trials were adapted to take this information into account. It was made clear to drivers that ISA is only a driver aid, and that they were responsible for control of their vehicle at all times and ensuring that they did not travel above the posted speed limit.
“Passengers were generally more accepting of the system once its purpose had been explained.”
The results of the trial were largely positive. TfL bus drivers demonstrated increased compliance with local speed limits, although this compliance was less common on downhill stretches of road. There were no adverse effects on driver behaviour reported after the technology was fitted.
Although there was no significant effect on fuel usage during the ISA trial, there was some evidence of improved emissions in 20mph zones and data-modelling indicated that there would be marginal safety improvements if ISA was installed within the TfL bus fleet.
Feedback throughout the trial showed that driver attitudes towards ISA improved as the trial progressed and their understanding of the technology grew. Some drivers reported experiencing an increase in negative attention from passengers and other road users who felt that the installation of ISA caused unnecessary delays; however, passengers were generally more accepting of the system once its purpose had been explained.
TfL experienced some problems with retrofitting ISA devices to vehicles already in service. This difficulty, and the high cost of rectifying the problem, led TfL to decide that vehicles needed to be fitted with ISA at the point of manufacture.
In recognition of the apparent benefits of ISA – for operators, drivers, customers and other road users alike – TfL has committed to fitting ISA as standard throughout its bus fleet. Although there were difficulties during the trial, the data collected helped to identify strategies that would negate these issues. TfL has now begun roll out of ISA on all new buses.
 New technology trials to transform bus safety in London, TfL, 2017
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