There is an established, positive relationship between vehicle speeds and road accidents. On rural roads, driving too fast for the conditions is more likely to be a factor in accidents than exceeding the speed limit. Encouraging drivers to drive at suitable speeds for the conditions is particularly important, since driver error is the major contributory factor in 95 per cent of accidents. A range of rural road safety engineering measures, in particular vehicle-activated signing, has been developed to encourage drivers to approach hazards such as bends and junctions at a safe speed, and to encourage them to comply with the speed limit, e.g. through villages. The signs display a message relating to road conditions such as these to just those drivers exceeding a set threshold speed. A study of the effectiveness of over 60 installations on rural roads in Norfolk, Kent, West Sussex and Wiltshire has been conducted by TRL for the Department for Transport (DfT). The trial aimed to assess the effect of the signs on speed and injury accidents, and drivers’ understanding of the signs. The results will be used to develop best practice for sign installation.The signs appear to be very effective in reducing speeds, particularly those of the faster drivers who contribute disproportionately to the accident risk, without the need for enforcement such as safety cameras. In this study, a substantial accident reduction has been demonstrated.