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SAQ, a device to measure and evaluate transverse unevenness due to ruts in asphalt roadways, is described. This is a mobile system used to record horizon referenced transverse profiles in a drive/stop process. It includes a microcomputer for processing all relevant parameters on board the measurement vehicle. Methods of the automated profile analysis are discussed, and different characteristic values for the evaluation of transverse unevenness are proposed.
Tracking and hydroplaning effects are caused by ruts which may affect traffic safety. In wet weather, skid resistance and the effects of transition zones (areas where the transverse slope changes) also have an influence on the accident figures in conjunction with the rutting problem. These parameters were investigated on a large number of autobahn segments. The results show that on roadways with mean and good skid resistance, accident rates under wet conditions tend to decrease as the rut or water depth increases. Only in transition zones, which feature unexpected obstructions to water run-off for the driver, is there an increase in the accident rate under wet conditions with increasing hypothetical water depth in the ruts. In addition, the accident risk in transition zones under wet conditions is also generally higher. The skid resistance always has a dominant effect on the accident rate under wet conditions. For road-maintenance measures, skid resistance therefore must be accorded clear priority over transverse unevenness.
flank slope of ruts, mean transverse slope, obstruction to water run-off, roadway surface maintenance, rut channels, rut depth, ruts, skid resistance, traffic safety, transition zone (change of cross-slope), transverse unevenness, water depth (hypothetical), water ponding
Head of Section Surface Characteristics, Federal Highway Research Institute, Bergisch Gladbach,