Opredeljena je kot geometrijska sled najvišjih stičnih točk med ravnilom dolžine 700 mm in odbijačem, kadar se ravnilo, nameščeno vzporedno z navpično vzdolžno ravnino vozila in nagnjeno nazaj za 20°, vodi ob prednjem delu vozila, pri čemer je v stalnem stiku s tlemi in površino odbijača (glej sliko 1a).
It is defined as the geometric trace of the upper most points of contact between a straight edge 700 mm long and the bumper, when the straight edge, held parallel to the vertical longitudinal plane of the car and inclined rearwards by 20°, is traversed across the front of the car, while maintaining contact with the ground and with the surface of the bumper (see Figure 1a).