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During wet weather operating conditions, tire hydroplaning can occur, potentially altering the handling characteristics of a vehicle. The rear tires of the vehicle run in a path previously cleared by the front tires under some operating conditions. Although path clearing has been previously demonstrated both analytically and qualitatively, it is difficult to estimate the changes in the tire/road coefficient of friction resulting from path clearing because of the complexity of the hydroplaning flow regime. In the present work, we utilize wheelspeed information captured from the vehicle CAN bus and photography to examine potential variations in tire/road coefficient of friction that result from path clearing. Results suggest that differences in friction availability may result from such path clearing. Maneuvers performed include steady-state cornering tests, straight-line braking and ISO lane change maneuvers.

An experimental program to measure braking characteristics developed under emergency braking conditions by ABS-equipped vehicles was designed and performed. Variables examined included initial braking speed, vehicle type, tire pressure and data recording equipment utilized. All experiments were conducted on a closed airport taxiway constructed of sharp, brushed and heavily striated concrete. Tests were conducted with and without activated ABS systems on the test vehicles. Results showed that (1) with the ABS activated, faint roadway markings were visible only under a very few special circumstances, (2) tire/road μ-values and corresponding deceleration values varied only slightly for differing speeds and ABS conditions, (3) tire pressure made little difference in limited test results, and (4) there were differences in recorded results depending on the equipment used for data acquisition.