Chevron markings were trialled on the M1 motorway in the early 1990s. A 15 per cent. reduction in the number of drivers following too close to the vehicle in front was observed in the lanes that were marked. Improvements in close-following were also observed in the unmarked, outside lane. Following the trial, advice and guidance about the use of chevron markings was published. Monitoring is continuing but no further assessment has been made of the effect of chevron markings on driving standards.