Practical Implications of Modeling Commercial Vehicle Empty Trips

Abstract

Implications of modeling commercial vehicle empty trips are discussed, a theoretical derivation for parameter estimation is provided, and insight is given into the order of magnitude of estimation errors because of the improper modeling of commercial vehicle empty trips. A set of relatively simple cases was designed to illustrate the most important implications. Also addressed are estimation errors from using naïve approaches to compensate for the lack of explicit modeling of empty trips and the errors associated with more advanced empty trip models. In the simplest simulation, directional errors for a basic complementary model were from three to six times fewer than those for the naïve models. In the more complex case, a more sophisticated complementary model performed slightly better than the basic model and both complementary models were considerably better than the naïve approaches. The directional errors for the naïve models were four to seven times greater than those for the complementary models. Moreover, an analysis of the statistical distributions of the errors indicated that the complementary models had higher probabilities of producing accurate results, whereas the naïve approaches had higher probabilities of producing very large errors. These analyses indicate that the naïve approaches translate into significant errors in directional-traffic estimates. For that reason, their use should be discontinued in favor of the more advanced models presented.

Characterization and analysis of metropolitan freight patterns in Medellin, Colombia

“…As shown, in terms of daily trips, 17,550 commercial vehicles enter, leave, or pass through the metropolitan area, and 22% of the total trips are empty. This proportion of empty trips is a typical pattern in Colombia and other countries [6][7][8][9]. Moreover, in terms of freight trips, the results show that only 10% of daily trips are external trips, the remaining 90% are internal.…”

Estimating Freight Flows for Metropolitan Area Highway Networks Using Secondary Data Sources

“…A particular issue is the difference in the share of import/export and through truck traffic across metropolitan areas. The fundamental problem with trip-based models is that they implicitly assume that the vehicle trip is the unit of demand, rather than the commodity being transported (Holguin-Veras and Zorrilla 2006). Hence they are not modeling the underlying economic supply and demand.…”

The Colombian Strategic Freight Transport Model Based on Product Analysis

“…As discussed earlier, there are limitations when estimating freight trip flows from commodity flows, as the latter do not specify the type of commercial vehicles used in freight transport [9,[24][25][26]. For instance, there are small (2 axles), medium (3-4 axles) and large (5-6 axles) trucks.…”

“…Empty trips cannot be estimated directly from the commodity flows as only loaded trips are included and there are routing patterns to be considered [25]. To overcome these limitations, additional models that represent empty trips as a function of the choice routes for commercial vehicles could be developed.…”