A skid mark is a black stripe on the road surface caused by rubber abrasion from a blocked or severely braked tire and by exudation of the binding agent ( bitumen ) from the asphalt surface . Usually, a skid mark is drawn on a dry road from a deceleration of 6 m / s².
The wheel can lock up for two reasons:
- Full braking with locking wheels
- Deformations on the chassis or body, due to which one or more wheels can no longer rotate freely.
The use of anti-lock braking systems (ABS) and vehicle dynamics control (ESP) in motor vehicles changes the formation of braking marks. In passenger cars, depending on the type of braking and the vehicle used, the use of ABS has almost no influence on the formation of skid marks. Depending on the quality (regular frequency) and adjustment of the ABS, a brake track can be interrupted at regular intervals (often on trucks ). When using ESP, the brake track can have transverse grains, which indicate control interventions on the wheels and the slip angle of the wheels.
Conclusions about the course of accidents can be drawn from the length and course of a skid mark:
- The initial speed of the vehicle can be determined from the length, taking into account the road surface and the weather .
- Sudden changes of direction in the course of a braking lane show the exact point of impact of the vehicle on an obstacle.
- Missing skid marks can indicate technical causes or failure of the driver to react.
- The nature of the skid marks (structure, grain) provides information on the tire pressure and the intervention of control systems.
Skid marks are therefore an important piece of evidence in solving the question of guilt after traffic accidents. Often they (and other traces of the accident, such as scratch marks, paint wear, splinters, deformation of the body, etc.) are recorded by measurement methods, whereby accident photogrammetry ( i.e. the evaluation of accident photos) is particularly important.
In addition to the locking of the wheels, side drifting or skidding of the vehicle is another cause of tire tracks on paved roads.
- Car tire tracks under the influence of the ABS and ESP control systems and the parameters of tire type and tire pressure . In: Verkehrsunfall und Fahrzeugtechnik, issue 4/2009, pp. 116–123 and issue 5/2009, pp. 166–175.
- Car drift and skid marks under the influence of the ABS and ESP control systems and the parameters tire type and tire pressure . In: Traffic Accident and Vehicle Technology . tape 7-8, 9 , no. 47 , 2009, p. 252-260, 285-293 ( vkuonline.de ).