A common method used by accident investigators to study the drag factor of a vehicle/surface involved in a crash is to carry out in situ testing using a substitute test vehicle equipped with a velocity/deceleration logging device and/or a chalk gun attached to the test vehicle. This approach provides a drag factor rather than a surface friction value and is of more use to the investigator as it provides a macro evaluation of the surface which is under investigation. It is well established that surface condition (wet/dry), vehicle tyre type, vehicle curb mass and surcharge load are some of the more important variables which must be taken into account when carrying out skid testing. Unfortunately it is often beyond the capacity of the investigating team to duplicate the actual accident conditions and testing is carried out, for example with police vehicles. This paper attempts to provide some guidance for when converting drag factors for different vehicle weights. The study reported here considered the emergency stopping ability of a range of family passenger vehicles. The conditions of testing were wet and dry asphaltic concrete with the vehicles in two different load configurations. (A) For the record of the covering entry of this conference, please see IRRD abstract No. 868510.
Abstract