Assessement the arrestor bed needs in downwards based on reliability principles

Abstract

In steeped downwards there exist the probability that heavy trucks were affected of cut brakes. In this situation, driver loses speed control downward, increasing speed up to 120 km/h or more and the crash risk increases. The arrestor beds are devices that provide contention to out-of-control trucks in downwards. This paper proposes a method to estimate the need of arrestor beds, based in the brake temperature profile, the weight of heavy trucks and the road geometry. The method is applicable in the geometric design and for road operation. In the first case, geometry is assessed using the entrance speed at the downward. In the second case, a dangerousness index is proposed based in reliability principles to estimate failure probability. Examples are presented considering trucks of 45, 60 and 70 tons of weight with different brake power. The index and criteria proposed are flexible and permitted to the designer to estimate the dangerousness of downwards and to design arrestor beds.