Intelligent Speed Assistance (ISA)

  • Published: European Transport Safety Council (ETSC) (2013)
  • Authors: European Transport Safety Council (ETSC)
  • Date Added: 05 May 2017
  • Last Update: 05 May 2017
  • Format: pdf


Define ISA


N/A: Guidance document

Key Findings:

  • Intelligent Speed Assistance (ISA) is the term given to a range of devices that assist drivers in choosing appropriate speeds and complying with speed limits. Intelligent Speed Assistance technologies bring speed limit information into the vehicle. Drivers receive the same information that they see (or sometimes miss seeing) on traffic signs through an on-board communication system, helping them to keep track of the legal speed limit all along their journey. Information regarding the speed limit for a given location is usually identified from an on-board digital map in the vehicle. Other systems use speed sign reading and recognition.

    • The information is then communicated to the driver in any of the following three ways:

    • informing the driver of the limit (advisory ISA),

    • warning them when they are driving faster than the limit (warning ISA) or

    • actively aiding the driver to abide by the limit (assisting ISA).

  • All ISA systems that are currently being used in trials or deployment can be overridden if wished by the driver. In contrast to ISA, a speed limiter is a device used to limit the top speed of a vehicle.

  • Up to 30% of drivers exceed speed limits on motorways, up to 70% on roads outside built-up areas and as many as 80% in urban areas. ISA can help to improve these high levels of non-compliance. Studies and trials undertaken in high performing countries (UK, NL, SE) show the positive effect of ISA on safety in these Member States. ISA is likely to have an even greater impact on safety and reducing speeds in countries where speed compliance is lower.

  • Citizens across the EU have a right to know what the speed limit is at all times on all roads, for reasons of general information and specifically for reasons of road safety. There are currently sections of road where this is not clear. ISA also needs up-to-date speed information. One source of this are speed limit maps provided by public authorities. A number of countries including Finland, Sweden and the Netherlands have both the speed limit map and procedures in place to keep this information updated and accessible.

  • ISA is a mature technology that has substantial safety benefits and potential to reduce the consequences of most severe collisions. ISA is steadily making its way into European vehicle fleets. A number of vehicle manufacturers already offer advisory ISA. Moreover, many hand-held navigation devices have advisory ISA applications, informing the driver about the correct speed limit. These two developments mean that drivers are becoming used to having this sort of information in the vehicle.

  • ISA has been extensively studied in Europe in large field tests. Over the last two decades, field trials have been carried out in eleven European countries: Austria, Belgium, Denmark, Finland, France, Hungary, Netherlands, Norway, Spain, Sweden and the U.K.


Intelligent Speed Assistance (ISA), Legal speed limit, Speed limit map.