Intelligent Speed Assistance (ISA)

Intelligent Speed Assistance (ISA) is an Advanced Driver Assistance System (ADAS) that is designed to prevent drivers from exceeding speed limits and is proven to work. Tackling speeding through technology is vital to saving lives and helps the effectiveness of all other crash prevention and mitigation systems because the faster we go, the less time we have to avoid a crash, and the harder we hit.


ISA works by using GPS combined with a digital map of speed limits to keep vehicles to the posted speed limit on each road. Different ISA systems utilise different methods to try and achieve speed compliance:

  • advisory ISA gives the driver immediate feedback through a visual, audio or haptic signal if the speed limit changes or they exceed the speed limit
  • voluntary ISA automatically limits engine power if the driver exceeds the speed limit, but the driver can override this
  • mandatory ISA automatically decreases acceleration if the driver exceeds the speed limit, and cannot be overridden 


Legislation to mandate ISA

Vehicle safety requirements are an EU competence and are detailed in two key documents, the General Safety Regulation (EC) No 661/2009 (or GSR) and Pedestrian Safety Regulation (EC) No 78/2009 (or PSR). These regulations were last updated in 2009 and the EU has identified a need to revise them to help arrest the stagnation in road safety improvement.

Through the revision of the GSR, the European Commission is seeking to mandate ISA, and other lifesaving ADAS technologies, such as Autonomous Emergency Braking (AEB) and Lane Keep Assistance (LKA), on new vehicles. Brake is supportive of this move, with analysis by TRL estimating that the package of measures being considered would prevent 25,000 deaths and 140,000 serious injuries over 16 years, if delivered in full.

The form of ISA being proposed for EU legislation is an over-rideable "advisory" system that warns the driver they are about to break a speed limit, through a ‘haptic’ vibration of their accelerator pedal, and controls the vehicle to under the limit unless the driver over-rides the ISA by pressing down the accelerator. For further understanding see this infographic from European transport charity ETSC.


Speed Limit Information (SLI)

There are proposals that argue a system called SLI (Speed Limit Information) is an ‘effective alternative’ that should be adopted instead of ISA. This is untrue according to the academics who have researched ISA. SLI is a far less effective system that warns drivers of their speed via a visual or audio message, and does not electronically act to keep a vehicle under a speed limit. TRL has shared evidence to the European Parliament that adopting SLI, rather than ISA, would result in 1,300 more deaths every year on roads.