Bimodal renewal processes models of highway vehicle loads

The distributions of the nowadays vehicle load of No. 110 PRC national highway, in Beijing, China is discussed, which contains a great deal of overloaded trucks in addition to normal vehicles. Traditional probability distributions with a single peak cannot describe this actual vehicle load appropriately. A bimodal distribution, with two peaks, consisting of a weighted sum of two normal probability distributions to describe different vehicle loads is developed according to acquired traffic load data. A filtered composite Poisson process and a filtered composite Erlang renewal process are used to describe the vehicle load processes consisting of both overloaded trucks and normal vehicles for the dense and general traffic states, respectively. Finally, 0.95 fractile of maximum distributions of this kind of vehicle loads in a 20-year residual life period for existing bridges on the national highway are used as their evaluation loads.