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One of the actions designed to increase road safety is the adoption of Intelligent Speed Adaptation (ISA). In essence, an ISA system constantly monitors both the vehicle speed and the local speed limit on a road and takes action whenever the vehicle is detected to be exceeding the speed limit. An Advisory ISA will warn the driver when he or she is speeding. The system can also be linked to the vehicle engine and perhaps brakes, to curtail speed to the speed limit while still allowing the driver to override the system (Voluntary ISA). A Mandatory ISA does not allow the driver to override the system (also called Non-Overridable ISA).

Projects and applications

Several FOTs on ISA have been conducted during the past ten years. Some of the trials only focused on Advisory ISA, others investigated the voluntary version, while some projects in particular aimed at comparing the effects of the different ISA options. A more recent project, the Danish ‘Pay As You Speed’ FOT, researched the effect of a combination of a speeding warning with financial incentives. Speeding was recorded and reduced the promised bonus of 30% on the insurance rate of the driver. Most FOTs used on-board devices, but also nomadic (off-board) devices are considered: the pan-European project TeleFOT, the Swedish MOTION project and the Lancashire ISA Project in the UK are using mobile phones and/or navigation devices for an advisory ISA. The main research objectives of these FOTs have been to understand how drivers use the system, and to investigate the effects of ISA on driver behaviour (with a particular focus on speeding) and the acceptance of different ISA systems among drivers. As a next step, some projects have used the FOT results (as part of a larger study) to assess the societal safety impact of ISA and have performed cost-benefit analyses. More recent projects have also investigated the impact of ISA on fuel consumption, i.e. carbon emissions (e.g. the UK ISA).

Assessing the benefits of ISA

The general finding of the ISA trials is that the system does reduce speeding among all categories of drivers, with Mandatory ISA showing the highest effects and Advisory ISA the lowest. The FOT results also seem to coincide in the fact that ISA effectiveness differs due to sex and age of drivers. The UK ISA reports even state that there is a tendency for the ISA to be overridden the most by those drivers who would benefit the most, i.e. young and male drivers with the tendency to speed. In general, the acceptance of ISA among drivers was found to be split, ranging from hostile ‘would-never-use’ drivers to those appreciating the safety potential. Those projects that have tested the system on several road categories come to different results regarding how system effectiveness varies by road type (motorways, rural roads, built-up area, etc. Differences might partly relate to different pre-ISA speeding behaviour on different road categories in the test countries. In general, transferability of the field trial results to other contexts is limited. More detailed comparisons between the FOT results are difficult due to differences in many test parameters: first of all, the ISA settings varied significantly between the trials. This does not only refer to the advisory, voluntary or mandatory ISA, but also for example to the speed exceedance at which a warning or intervention is triggered. In the Swedish MOTION project for example, drivers could change the default settings; the majority chose to be warned at 5-10 km/h above speed limit.

Open issues

Despite the predominantly positive findings on the safety potential of ISA, no country so far has established legal requirements for vehicles to be equipped with ISA. A major reason probably is the lack of user acceptance for a mandatory ISA, which would have the highest impacts. In the UK, research commissioned by the Department for Transport (and based on the UK ISA results), investigated a market driven scenario for deployment of (advisory) ISA and an authority driven deployment scenario (starting with voluntary, later on mandatory ISA). Results clearly indicate that for any scenario the benefits considerably would outweigh the costs, with a significantly higher safety potential and a better cost-benefit ratio for the authority driven approach.

Source of information

FOT-Net Brochure, November 2010

List of ISA FOTs

"ISA" is a category of the FOT Catalogue. To see the full list of FOTs by countries, go back to the FOT Catalogue. To look at other FOT Categories, see also the catalogue of FOTs by categories.

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