On the comparative performance of urban delivery vehicle classes

As it is widely known, a large truck generates more pollution and congestion than a small truck, which is an obvious consequence of its larger size. However, it is frequently overlooked that they have very different cargo productivities, and that large trucks require less trips to transport the same amount of cargo than small trucks. As a result, large trucks could produce less social costs than small trucks, as long as they generate proportionally less traffic. The objective is to identify the conditions under which large trucks are the most beneficial in terms of social costs. To gain insight into the nature of these tradeoffs, a mathematical formulation was developed to express social costs as a function of a multimodal vector of traffic flows. The key insight gained is that large trucks could indeed be better in terms of social costs if they replace a sufficient number of small trucks.