Lane Departure Warning Assistant (LDWA) systems warn drivers when they leave their traffic lane unintentionally. A field operational trial (FOT) was initiated in the Netherlands in order to determine the potential LDWA effects on road safety and road capacity. This report decribes the FOT results. It is shown that LDWA systems will have a slight positive impact on road safety. A positive road safety effect also means a marginal impact on incidental congestion because of a reduction in accidents. The maximum effect on traffic safety is a 9% reduction in casualties sustained in accidents involving heavy goods vehicles or busses on 80, 100 and 120 km/h roads in rural areas. There is no direct LDWA effect on structural congestion or on road capacity. However, a reduction in accidents implies a maximum reduction of 11% of delay and traffic queues resulting from incidental congestion. If LDWA systems are used in situations where an extra lane is added by using the emergency lane and/or narrowing existing lanes, there may be a slight positive effect. The LDWA effect on traffic safety and traffic flow is probably somewhat optimistic due to the following: (1) 100% penetration in the heavy goods vehicles (HGV) sector in unlikely; (2) Drivers cannot prevent all side-swipe and run-off road accidents, even if the LDWA system warns of an impending lane departure; and (3) the expectation is that a part of the positive LDWA effect will disappear in time.
Abstract