Collision avoidance systems

A considerable amount of research is addressing eSafety systems of the future. Much work is being carried out on technologies such as collision avoidance systems but their usefulness in addressing high-risk crash scenarios typical of most European roads as well as their feasibility has yet to be determined.

Research on collision warning and collision avoidance systems is taking place in Japan, the United States and in the European Union within the European Commission's eSafety programme. Very large estimates of the safety potential of such systems have been claimed following laboratory studies, but the range of technical and behavioural issues involved in many of the concepts require full on-road assessment. To be practical, most of the proposed systems require a well controlled traffic situation, such as that found on motorways, but where the casualty reduction potential is relatively low. For an overview of key issues [41]OECD, 2003 Road safety: impact of new technologies.

Various systems are under development:

Forward Collision Warning

Is a system which comprises a visual and audible warning that the driver is too close to the vehicle in front. The warning depends on how long the distance is between the vehicle and the vehicle ahead. The level of warning changes from "safe" to "critical" as the following distance decreases.

The Reverse Collision Warning System

Is a visual and audible system which warns drivers about the likelihood of collision with an object behind the vehicle by means of sensors in the rear bumper. The warning intensifies when the distance between the vehicle's rear and the object decreases.

Adaptive Cruise Control (ACC)

Enhances automatic cruise control found in many new vehicles by automatically maintaining a set following distance to the vehicle in front. The distance to the preceding vehicle is measured by radar, laser systems or both. When the speed of the vehicle in front is slower than the adjusted speed, the ACC system adjusts vehicle speed to allow a safe distance to the lead vehicle.

Collision Mitigation by braking

Is an evolution of ACC with the addition of a braking system that increases headway by braking; these systems may also detect obstacles within the road and brake accordingly. The speed and separation distance at which the systems operate is determined by the arrangement and type of sensors and the recognition ability of the systems.

Lane-Keeping Devices

Are electronic warning systems that are activated if the vehicle is about to veer off the lane or the road. Times to collision in safety-critical lane changes are normally much less than one second. Since mean driver reaction time is about one second, there is not sufficient time for a driver to respond to a warning before crashing. Because there is insufficient time for reaction to a warning, lane change and merging crashes can probably only be avoided by intervening systems. But these have their own problems: how to detect driver intentions and how to intervene. This may be by taking over the steering from the driver or by providing feedback through the steering wheel. The technical and operational feasibility of such systems has still to be demonstrated. Most existing systems are warning only systems.