Real-world testing of intelligent speed assist (ISA) systems has highlighted a regulatory gap in how they are currently evaluated for approval in the UK and Europe.

ISA, which uses camera and GPS data to read speed limit signs and communicate the prevailing limit to the driver, became mandatory on new vehicles sold in the UK and European Union from July 2024. 

While ISA has the potential to play a significant role in improving road safety, findings from Thatcham Research suggest the current regulatory framework can leave gaps in how performance is captured, which may reduce driver confidence and lead some to disengage the system.

Under current EU regulation, ISA systems are assessed based on accuracy over distance travelled. While this provides a useful baseline, it can overlook performance at key moments, such as when speed limits change.

Thatcham Research’s event-based approach measures accuracy at each of these change points.

When applied in real-world conditions across three vehicles, this methodology highlighted a different level of performance compared with the distance-based standard.

The worst performing vehicle in real-world testing scored 91.3% accuracy across the driven distance. When assessed on an event-based metric, the system was 74.3% accurate.

This means that for roughly one-in-four events, ISA is displaying the wrong speed limit, which Thatcham Research says is below the level of performance for most drivers to accept and trust the technology.

The best performing vehicle in real-world testing scored 98.39% accuracy across the driven distance, which implies a near-perfect system. This same vehicle’s event-based accuracy was 90.3%.

With roughly one-in-10 events being incorrect, even systems which perform comparatively well on UK roads are still not good enough for widespread acceptance, according to Thatcham Research.

When ISA misreads speed limits, it says it can lead to unexpected or inconsistent system responses.

Over time, it argues this risks reducing driver confidence in the technology, which is critical to achieving its intended safety benefits.

In the case of all vehicles, ISA displayed speed limits which are not legal in the UK. Multiple instances of 5, 10, 15, and 100mph displayed speed limit were observed.

Displaying speed limits which are not plausible erodes driver trust and can lead to increased collision risk if linked to the vehicle’s ACC (adaptive cruise control) system, which can cause unwanted harsh braking or acceleration.

Further information:

https://www.fleetnews.co.uk/news/regulatory-gap-affecting-intelligent-speed-assist-performance