Wet road skidding resistance at high speed on a variety of surfaces on A1.

The measurements on A1, togheter with additional measurements of braking force coefficient on other high speed roads, suggest that there is little difficulty in obtain ing the suggested minimm braking force coefficients of 0.4 at 30 mile /hand 0.3 at 80 mile/h in the fast lane of motorways and fast dual carriageways, but in the slow lanes which carry much heavier traffic, there are clearly likely to be problems both.