The potential for accident reduction by improving urban skid resistance levels.
The problem of providing adequate wet-road skid resistance on urban
roads has received relatively little attention from highway maintenance
authorities. This study is an assessment of the potential for reducing
accident rates by improving skid resistance levels on such roads.
Reasons for the neglect of urban skid resistance are discussed and an
assessment made of the scale of the skidding problem in this context.
Evidence is presented to demonstrate that the potential for accident
reduction is greater than is indicated by the statistics for reported
skidding accidents. The pattern of frictional demand and the
measurement of skid resistance are discussed, as are the technical
difficulties associated with maintaining good skid resistance on
heavily-trafficked roads. The performance of conventional surfacing
materials is assessed and recently-developed materials are evaluated.
It is suggested that the attainment of high skid resistance is inhibited
by economic rather than technical factors. Nationally-proposed
standards for skid resistance are examined and modifications are
suggested for urban use. The problem of defining accident risk at an
individual site is examined and the relationship between accident rate
and skid resistance investigated using regression techniques with data
from the Greater London area. Criteria are developed for identifying
sites where an improvement in skid resistance is likely to be effective
in reducing accidents and consideration is given to the economic
justification for skid resistance improvements. Alternative strategies
are considered and a policy is proposed which would be practicable and
cost-effective and, it is argued, could lead to a substantial reduction
in accident rates.