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Intelligent Speed Limiters

Intelligent Speed Adaptation - ISA

Intelligent Speed Adaptation (or sometimes referred to as Intelligent Speed Assistance) is a system by which the vehicle "knows" the permitted or recommended maximum speed for the road it is traveling on. The purpose of ISA is to assist the driver in keeping to the lawful speed limit at all times either by alerting the driver when they exceed the speed limit or, by automatically reducing or limiting the vehicle’s speed as they pass through different speed ‘zones’.

There are fundamentally two types of speed adaptation systems – Passive and Active. The fundamental difference between passive and active ISA is that passive systems simply warn the driver when the speed limit has been exceeded whereby, active systems automatically correct the vehicle’s speed.

Passive ISA – passive ISA simply warn the driver when they exceed the speed limit for that section of road they are driving on. This allows the driver to make a choice as to what action to take.
Voluntary ISA – voluntary ISA provides the driver with the ability to override or disable the ISA system if necessary.
Mandatory ISA – does not provide the capability to override or disable the ISA system.

How does it work?

ISA utilises GPS (Global positioning Satellites) and a digital map containing the speed limits of the road network. The ISA device uses the GPS system to determine the vehicles position, compares its position with the digital map, and, if it is an active ISA system, reduces or limits the vehicles speed to that based on the digital map.


The benefits that ISA can deliver are summarised as:

ISA can bring substantial safety benefits;
ISA can also reduce fuel consumption and other pollutant emissions form vehicles – including noise;
ISA is a cost-effective road safety measure;
Test drivers show a high acceptance of the different types of ISA trialed and often wanted to keep the system after the trial;
ISA technologies are robust, reliable and ready to be implemented;
More specifically, for the fleet operator, the specific benefits are:

Health and Safety/Duty of Care

A duty of care towards drivers and other road users is top of most fleet operators' responsibilities. Existing health and safety legislation is about to be joined by the Corporate Manslaughter Bill, putting even greater emphasis on the need to assess, monitor and reduce risk. By deploying active ISA, a fleet operator can significantly reduce the risk of fatal accidents of their vehicle drivers.

Overseas and local trials show that ISA can be effective in reducing excessive speeding in motorists and thereby reducing injuries, fatalities and the costs associated with speed related accidents. The official report into ISA commissioned by the Department for Transport estimates that deploying active ISA can reduce the risk of fatal accidents by up to 29%.

Improved fuel economy/Reduced CO2 emissions

A number of trials and real-world experience of vehicles fitted with active ISA have achieved reductions in fuel economy. Realistic improvements in fuel economy can be expected to be around the 8% figure. These trials have also indicated that reductions of between 8 - 12% in CO2 emissions would be achievable.

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