Steep downgrades are known to increase accident rates yet little is published on how well vehicles brake and handle on steep downgrades. In this study braking tests were completed on grades of 1, 7, 13, 21 and 28 percent.The tested surfaces were asphalt, in both dry and wet conditions, with a car and a utility vehicle, with and without Anti-Lock Braking Systems (ABS) brakes. The 13 percent grade was grooved and the test sequence repeated.The braking tests found a non-linear decreasing relationship between the average coefficient of friction or drag factor and downgrade. Pavement grooving on the 13 percent grade of a local road has eliminated the crash occurrences for a two-year period. Testing showed that grooving also improved vehicle handling. (A)
Samenvatting