What is Lane Departure Warning (LDW) and what effect does it have on road safety?


A Lane Departure Warning (LDW) system measures the distance to the lane lines and warns drivers if they drift towards these lines too closely or too fast. The system assists in lane keeping for example by monitoring length (axis or edge) markings by means of a camera. Good-quality markings are essential to reliable functioning of the system. Warnings may be auditory or may be given by means of a steering wheel signal (haptic). There are also Lane Keeping Systems (LKS), that autonomously correct the direction of the car. Almost one third of all registered road deaths (2005-2009) are road shoulder crashes (see the archived SWOV fact sheet Run-off-road crashes).

An unknown share of head-on (multiple) collisions is the result of a manoeuvre by the driver to steer back to the centre of the road but oversteering to the wrong side of the road. A system preventing cars from veering off the road could therefore be very effective.

A study for the European Commission into the costs and benefits of new vehicle technologies [10] concludes that making LDW for cars and delivery vehicles (category M1/N1) mandatory should not be recommended: the costs are expected to outweigh the benefits of prevented crashes. In various studies, positive effects of LDW are expected, but Hynd et al. [10] discuss an American study based on field data which does not show any crash reduction. That is why the cost/benefit calculation assumes the absence of any effect. For trucks and buses (categories M2,3 and N2,3) Hynd et al. arrive at a slightly higher maximum effect of LDW. Jänsch [27] concludes that the effectiveness of LDW remains unclear.

In addition to the warning LDW system, there are also interventionary, redirecting Lane Keeping Systems (LKS). For these systems, the benefits are expected to outweigh the costs [10]. Dat wordt mede ingegeven door de door Hynd et al. [10] These expectations are partly based on the American study discussed by Hynd et al. [10] which indicate a positive effect of this system in actual traffic. Hynd et al. do, however, draw attention to the potential problem of acceptance among users.

Presumably and partly based on these findings, the European Commission has, for its new regulations concerning type approval of motor vehicles [9] proposed making an interventionary LKS mandatory for cars and delivery vehicles and a warning LDW system for lorries and buses.

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Intelligent transport and advanced driver assistance systems (ITS and ADAS)

Intelligent transport and advanced driver assistance systems are implementations of information and communication technology in vehicles… Meer

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