Abstract
The traction forces transmitted in the rail-wheel contact have a decisive influence on the performance potential of rail vehicles. External factors such as humidity or the contamination of the rail surface have an adverse effect on the maximum transmissible traction forces. In order to counter the effect of these effects, sand is usually spread in the wheel-rail contact area. While this increases the friction coefficient (i.e. the relationship between the wheel normal force and the longitudinal force in the contact area), too much sand can lead to failure in track occupancy detection systems. The tests described in this paper are intended to provide an insight into the extent to which the material output rate of sand influences the friction coefficient.