A trial of motorway Chevron markings, to help drivers to choose a safer following-distance, was conducted by Halcrow Fox and Associates for the Transport and Road Research Laboratory during 1990 and 1991. Chevron markings consist of a series of white arrow heads on the road surface at 40 metre intervals and are accompanied by roadside signs advising drivers to "Keep Apart, 2 Chevrons". They were devised and first used in France. The UK trial involved measuring vehicle spacings and speeds at two sites on the M1, coupled with public interview surveys. The Chevrons produced an improvement in close-following behaviour at both sites, apart from an anomaly at one downstream monitor. Results suggest that a reduction of about 15% in the percentage of drivers close-following at less than one second over the Chevrons might be expected after the initial "novelty" effect has worn off. It was established from the interview surveys that most drivers understood the markings and tried to use them. The majority did not experience a difficulty in doing so. There may have been a reduction in accidents associated with the introduction of Chevrons, but the result is based on only six months of After data.

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