Should vehicles warn you if you break the speed limit?

All new vehicles sold in the EU will need to include technology to either warn or prevent drivers from speeding from 2024. It’s called Intelligent Speed Assist (ISA) and can use different methods to detect the speed limit on the road the vehicle is travelling on.

Most vehicles are likely to use forward-facing cameras that read speed signs, while some will also use map data or LIDAR.

The automakers can choose passive or active methods. A passive method would be to sound a warning or create some kind of physical alert (e.g. vibrations through the steering wheel) if the posted speed limit is exceeded by a certain amount or for a certain time. More active methods could include making it more difficult to push the accelerator (i.e. causing the foot to lift off the accelerator without additional pressure being applied), or using software to reduce the speed.

Drivers will be able to override the system – there are technical and safety reasons for that. Firstly, cameras and other technology are not 100% reliable when reading speeds, particularly when there’s a lot of other signage, there are road works, signage has been vandalised, or signage doesn’t match the expected specifications (e.g. it’s obscured by dirt or snow, is not compliant with local codes, etc).

In effect, ISA is a driver assistance system which encourages drivers to drive within the law. Cars contain other systems like this, for example, a buzzer that sounds if the car is moving and the seatbelt isn’t fastened.

Should vehicles intervene in the case of speeding?

There are both legal and commonsense arguments that apply to speeding.

Speed limits are set by law to be a reasonable and realistic maximum speed that drivers should travel at when the weather conditions permit it. Penalties apply to drivers that exceed the speed limit by a certain amount, and the purpose of the speed limit is to reduce accident risk.

There are some compelling arguments in favour of temporarily exceeding the speed limits, most focused around during overtaking in order to reduce the time exposed to danger. I.e. it’s sometimes safer to exceed the speed limit than not.

Speeding is claimed to be a contributing factor in somewhere between 20-30% of fatal accidents, although this also includes using ‘inappropriate speed’ which could be under the speed limit, but not appropriate for the weather or traffic conditions. In this case, the speed limit itself wasn’t reached and a system to reduce speed that is over the limit would be ineffective.

What the stats don’t show is that a huge number of crashes where speed is an issue also involve one or more of the following:

• Alcohol
• Drugs
• Fatigue
• Reckless driving (e.g. street racing, fleeing from police)

In these cases you could argue that constraining the speed would minimise the harm.

It makes sense for a vehicle to warn a driver if they are speeding; it doesn’t make sense for the vehicle to actively intervene when the speed is not that much above the speed limit, unless there’s an imminent risk of a crash as this could create a scenario that the driver is not expecting or that causes danger.

There may be a compelling argument that if a person is travelling at an excessive speed above the limit that the vehicle should intervene. For example, 30mph above the limit. However, it still doesn’t stop scenarios where the system interprets the wrong speed limit.

Ultimately, a person needs to be in control of their vehicle. If speed awareness devices are used in conjunction with forward collision warning, autonomous emergency braking and other driver safety aids, this should reduce the risks of having a crash.