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Intelligent Speed Adaptation

Car's that won't break the speed limit

Whether you would consider it a gift from the gods or the complete opposite, a system that can prevent you breaking the speed limit is just around the corner. The technology is known as Intelligent Speed Adaptation or ISA for short.

How does ISA work?

Satnavs can already place you on a map, and know the name of the road you are on, and it's easy for them to be programmed to know the speed limit.

Once the car knows where it is and what the local speed limit is then all that's needed is a link to the throttle so the car won't go beyond the limit.

What could ISA do?

There are three alternative options for ISA:

  • Advisory – a simple device that tells you the speed limit, and gives a warning when you go over the limit.
  • Controlling – hard wired into the car so that it becomes impossible to break the speed limit.
  • Discretionary – a half-way-house, where you can switch between 'controlling' and 'advisory', or even switch the system off altogether.
Would fitting be mandatory?

Not at the moment, but if all worked well it would be expected to be, for new cars, at some time in the future.

The government would be most unlikely to require existing cars to be retro-fitted with such a device.

We would expect some businesses to fit ISA to their fleet cars or vans, possibly in advisory form. Then car manufacturers might start offering 'advisory' or 'discretionary' systems as optional extras.

If popular and effective on an optional basis then – as was the case with air bags, ABS brakes and electronic stability control – manufacturers might then start fitting ISA as standard, initially on more expensive models.

Car manufacturers are unlikely to fit 'controlling' systems unless there were legislation to make them do so.

Such legislation couldn't be a British decision alone as vehicle standards are regulated from Brussels. However, most new car technologies that prove effective in road safety terms have eventually become compulsory.

Euro NCAP to encourage fitment of ISA

ISA systems are set to become more widely available.

Since January 2013 ISA systems that meet Euro NCAP requirements have been awarded points that contribute towards the car's overall 'Safety Assist' rating.

New Euro NCAP protocols will award points for both advisory and discretionary ISA systems, depending on how they determine the local speed limit and how they communicate that information to the driver.

This is not the first time that Euro NCAP has helped drive the market by awarding points for safety technologies not required by law. Both Electronic Stability Control (which will have to be fitted as standard to all new cars since 2014) and seat belt reminders have been widely available for several years as a direct result of Euro NCAP encouragement.


What could go wrong?

One possibility is that an ISA system could apply the wrong speed limit, cutting motorway traffic to 30mph because of a close minor road for example, or allowing a car on the minor road to do motorway speeds.

Opponents will say that the merest chance of this should be enough to prevent the system ever taking to the roads.

Supporters on the other hand would argue that the motorway driver should be able to quickly notice the application of the lower limit and turn the system off, while traffic on the minor road would not be forced to accelerate, and the driver would have to make a conscious decision to do so.

ISA would only ever stop you exceeding the limit, or warn you of the maximum speed limit, so you would still have to continue to watch your speed and make sure that it is appropriate for the conditions and local situation.

How could ISA affect driving?

ISA could make overtaking difficult, and prevent accelerating out of a misjudged situation in some cases. But it can be argued that drivers would just have to remember to switch the system off when overtaking.

Similarly there could be problems if the speed limit changed to a lower speed during an overtaking manoeuvre, though again the system could be turned off, and you probably shouldn't be trying to overtake in such circumstances anyway.

It is possible that ISA could lead to 'bunches' of cars, all travelling at the same speed, with some drivers depressing the accelerator to the floor and driving just as fast as the car would let them. Most who have taken part in experiments with ISA systems have not done this.

What do drivers think?

Much depends on what sort of system is being proposed. In an AA-Populus poll of 17,481 respondents, 43% thought the compulsory introduction of 'controlling' ISA would be acceptable compared to 49% who didn't. So drivers don't want it forced on them.

But another survey showed that 61% of drivers said they would use a device to stop them exceeding the speed limit if one was fitted to their car. This suggests greater support for discretionary ISA. The AA also gets calls from members wanting to know how they can get hold of this system.

AA view

On balance, a voluntary, discretionary or advisory system probably has safety and practical benefits as it can remind us of speed limits and help prevent accidents and penalty points.

A mandatory, 'controlling' system would be a step too far as the human element of judgement must always govern our safe driving. Perhaps the best answer is to allow time, and the market, to take its course as has happened with other in-car systems.

Ultimately the best speed limiter is your right foot.

(Page updated 30 November 2012)