Commercial Vehicle Empty Trip Models With Variable Zero Order Empty Trip Probabilities

This paper considers enhanced formulations to model commercial vehicle empty trips. These formulations relax a limitation of the original trip chain models, i.e., the assumption of a constant probability of a zero order trip chain, p, for the entire range of trip types. The formulations considered in the paper assumed that p follows a logistic function of the opposing commodity flow, and trip distance. The consideration of a variable p significantly improves the relative performance of the models. The relative error for the models with constant p ranged from 4.2% to 19.3% higher than that for the models with a variable p as a function of either commodity flow or distance.