VEHICLE GUIDANCE BY DELINEATION SYSTEMS AT NIGHT

Car and road designs are considered to be better when they require less driver attention and allow drivers to behave more as a supervisory controller in coping with normal, multitask driving. In this paper an example is presented with respect to road design and, more specifically, with respect to various configurations of delineation on wet roads at night. The criteria for supervisory control are focussed on driver's observation strategy in terms of "free times" available for tasks beyond lateral vehicle control, on driver's control strategy in terms of amplitudes and frequencies of the steering-wheel movements, and on the overall driving performance in terms of variations in lateral position and yaw rate. The research findings on straight and curved roads recommend the necessity of using delineation devices at both sides of the traffic lane by the implementation of profiled stripes, of the centre and/or lane boundaries, or postmounted delineators just beside the boundary. Postmounted delineators on larger cross distances are less effective. The longitudinal spacing between the raised pavement markers has to be restricted up to 12 m for curves with radii of 200 m and up to 24 m for straight roads. For the covering abstract of the conference see IRRD 285907. (Author/TRRL)