AVZ Blog: Speed limiters in action – Findings from London and New York City

26th February 2023

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Key points

  • Findings from two trials of retrofitted speed limiters has shown how speeding can be drastically reduced.
  • Both London and New York City are keen to roll out Intelligence Speed Assistance (ISA) wider.
  • Other authorities, including Leeds City Council, are also interested in leading by example with ISA.
  • Transport for London (TfL) is lobbying for ISA to be included in the UK’s vehicle safety regulations.

Road danger reduction requires speed reduction. This includes a reduction in the incidences of speeding. Speed limiters allow compliance with speed limits to be designed in, rather than enforced externally.


In 2021, TfL started retrofitting ISA technology into its commercial vehicle fleet. Produced by Sturdy Corporation, the technology limits the top speed of the vehicle. It does not apply the brakes nor increase the vehicle speed (if the vehicle is travelling below the speed limit).

A total of 360 TfL vehicles had ISA retrofitted by March 2022. The results below are based on approximately two years of data (June 2020-July 2022).

Findings included:

  • A 62% reduction in speeding incidents. This ranged by speed limit with an estimated 60% decrease in speeding on 20mph roads through to an 89% drop on 60mph roads.
  • No increase in harsh braking, harsh cornering or harsh acceleration.
  • The average distance travelled and averaged journey time for each trip was reported to be largely unaffected.

It should be noted that whilst the number of speeding incidents were greatly reduced, there was minimal difference on how much over the speed limit the drivers did when they did exceed the speed limit. 

In light of the impact on speeding, TfL is looking to incorporate ISA more widely in its fleet.  This is in addition to the use of ISA on the London bus fleet. At present about 30% of the bus is fitted with ISA, with plans to retrofit ISA on a further 1,800 buses.

TfL is also calling on national government to include ISA in national vehicle regulatory type approval framework.

New York City

A New York City ISA pilot programme launched last August has reported. In this trial, vehicles were equipped with an override button that could disable the speed limiting technology for 15 seconds

This was used approximately 600 times, less than once per week per vehicle.

After 215,000 kilometres travelled by the 50 city fleet vehicles, the pilot reported:

  • 99% speed limit compliance.
  • 36% reduction in hard braking events.

Grant applications have been submitted to expand the ISA programme to 7,500 city fleet vehicles over the next three to four years.

Lessons for others

The London Vision Zero Action Plan Progress Report, published November 2021, had a core set of requests for boroughs. These included boroughs lowering speed limits as well as:

“Leading by example in committing to eliminating casualties on our streets, through supply chains and fleets.”

There is interest in ISA outside of London. As seen below, Leeds is one of the other authorities interested in retrofitting speed limiters to its vehicles and including a requirement for them in future contracts.

Leeds Vision Zero 2040 Strategy

Leading by example With around 33,000 employees, the council is one of the largest employers in West Yorkshire, and it has a fleet of more than 1,300 vehicles. Collectively, as a partnership, there are many non-emergency vehicles that could be retrofitted with in-vehicle technology to limit vehicle speed. We could also consider whether new vehicle contracts might include this technology as standard in future.

Going forward

Speed compliance is a vital part of speed reduction which is in turn key to reducing road danger. Action Vision Zero will continue to call for authorities to introduce ISA on their fleet and their contracts. That will be the quickest way of seeing the benefits of ISA.  For more information, contact jeremy or amy@ActionVisionZero.org

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