Activity-based model
empty freight vehicle trips. The number of empty trips is not negligible as it accounts for 30 to 40 percent
of the total truck trips [3]. Commodity-based approaches are more suitable since the amount of
commodities is converted to truck trips and become easier to integrate the empty trips into the modeling
framework. Holguin-Veras and Patil [3] is, for example, a commodity-based OD synthesis model
including empty trips when estimating freight OD matrices from the observed link volumes.