I drove a car with UK’s compulsory new speed limiter

All new cars sold in the UK will come with a Speed Assistance System (SAS), which will be mandatory in all cars, vans, trucks and buses sold across the EU

Jamie Brassington 08:21, 14 Jun 2025

All new motors sold in UK showrooms now come with 'compulsory' speed limiters, due to a shake-up of regulations by the European Union[1] (EU).

The EU[2] has introduced new ISA rules under its General Safety Rule (GSR) - which sets out the minimum safety standards required for vehicles and trailers.

Despite the UK not adopting the EU's GSR, manufacturers based in Europe are not removing ISA technology from cars destined for the UK, meaning British motorists will be affected by the changes.

Cars can be retrofitted with three types of ISA: informative/advisory, supportive/warning and intervening/mandatory.

Each one varies in the impact and control it has on the vehicle and driver.

The least forceful one is informative/advisory ISA which simply flashes a warning sign on the dashboard or makes an audible gong. Then there's supportive/warning ISA which increases the upward pressure on the accelerator - but this can be overridden by holding down the pedal.

The most forceful one is intervening/mandatory ISA, which limits the fuel injection inside the car to prevent a driver from speeding. ISA also works alongside GPS and traffic sign data, allowing it to know when to kick in.

The decision to incorporate Intelligent Speed Assistance (ISA) in vehicles destined for the UK has elicited a varied reaction from drivers.

Some motorists welcome it as a beneficial safety feature, while others worry it could deprive them of the power necessary to "get out of nasty accidents".

A portion of motorists perceive it as an unwarranted interference with their driving autonomy. Although ISA is capable of capping a car's speed, it's been noted that cars headed for the UK will be equipped with a 'softer version', which I reckon is a sensible approach.

From my perspective, the introduction of some form of mandatory ISA can be advantageous, but not to the extent where it encroaches on a motorist's liberty. Having personally tested a vehicle with a mandatory speed limiter on motorways, I can appreciate its intent.

However, during my test drive, a minority of drivers were less than pleased.

On a couple of occasions, frustrated drivers closed in on my tail as I maintained the legal speed limit.

With either a dashboard notification or added resistance to the accelerator pedal, it might encourage drivers to think twice about exceeding speed limits.

In peak traffic times, ISA could help reduce congestion by deterring motorists from speeding and following too closely.

References

1. ^ European Union (www.devonlive.com)
2. ^ The EU (www.devonlive.com)