The relationship between shoulder design and accident rates on rural highways.

Accident data was obtained from the fatal report forms completed by engineers of the New South Wales, Department of Main Roads.The exposure data was obtained from the NAASRA data base road inventory. The analysis showed that the accident rate of roads with unsealed shoulders was between three and four times the accident rate for roads with sealed shoulders.An examination of accident descriptions showed that losing control of vehicle on the gravel shoulder was suggested as a contributing cause in about 17 per cent of fatal accidents.