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It can happen, following a collision between a car and a pedestrian or in a deliberate assault with a motor vehicle, that the pedestrian comes to be caught or wedged beneath the car, and that the driver then travels on for a considerable distance, afterwards claiming to have been unaware of the presence of the person. However, police, lawyers and jurors are often incredulous that the driver should not have been able to “feel” that there was something underneath his car. The authors have investigated the matter by carrying out practical tests with suitable cars and dummies. This paper describes instrumented tests performed by the authors following one such incident, and gives accounts of two previous incidents investigated in a more subjective fashion. The general conclusion is that the effect on the behavior of the car is very small and that a driver might indeed be unaware that there was a person trapped beneath them.

The straight-line tire/road friction coefficients of three motorcycle tires designed for high-performance or sports motorcycles have been measured and compared with a representative ordinary car tire. Both peak and locked-wheel friction was measured on two different surfaces (hot rolled asphalt and stone mastic asphalt), dry and wet, at speeds between 32 and 100 km/h. Unexpectedly, a substantial difference between the friction of the car tire and the motorcycle tires was not found, and while the car tire did tend to deliver the lowest friction of the four, this was, with one exception, no more than the variation among the three motorcycle tires. Generally, on the dry surfaces peak friction coefficients of around 1.2 were found, with locked wheel coefficients of around 0.7-0.9. The exception was in the measurement of the peak friction on dry hot rolled asphalt, where the coefficient of friction of the car tire was about 0.2 less than that of the motorcycle tires.