Accounting for Commercial Vehicles in Urban Transportation Models

Summary Report

3.0 Definitions of Commercial Vehicles

This section presents the definition of the term "commercial vehicle" for the purposes of this study and summarizes the commercial vehicle categories.

3.1 Definitions

"Commercial vehicles" include a broad range of vehicle types that are used for commercial, rental, educational, and government services. Examples of the uses for such vehicles include: transportation of persons, package and mail delivery, urban freight distribution, utilities, trades and services, landscaping services, outside sales, product delivery, vehicle rental, transportation of school children, construction activity, and paratransit services.

Commercial vehicles demonstrate temporal and geographic distributions, which differ from those of personal vehicles. In traditional transportation planning studies, estimates of household vehicle trips are factored to correct for underreporting and under predicting of commercial vehicle trips in traditional transportation planning data sources. While traditional travel models are adequate for some basic analyses, improved methods for estimating commercial vehicle trips would provide capabilities for more accurate analysis of additional transportation planning functions and for the analysis of a wider range of transportation policies.

Many vehicles registered as commercial vehicles can be defined as commercial vehicles, but other vehicles falling into these categories are registered as private vehicles. For example, a realtor may register his/her automobile as a private vehicle but often use it for business purposes. On the other hand, many vehicles are registered as commercial vehicles but also are used for personal non-commercial purposes. Any vehicle used for commercial purposes is considered in this study as a commercial vehicle, regardless of how it is registered. It should be noted that vehicle registration rules and practices with respect to commercial vehicles differ by state, further complicating the separate identification of commercial vehicle usage patterns.

3.2 Categories

Commercial vehicles are primarily organized into three groups, based on what is being carried and the economic, demographic, and land use factors influencing the magnitude and distribution of commercial vehicle trips in a metropolitan area. The three groups are:

1. Commercial passenger vehicles;
2. Freight vehicles; and
3. Service vehicles.

The commercial passenger vehicles category includes school buses, shuttle services, rental cars, taxis, and paratransit vehicles. In general, growth of this category of commercial vehicles tends to depend on the growth of population and employment in a metropolitan area.

The freight vehicles category includes mail delivery, trash collection, warehouse delivery, parcel pickup and delivery, and construction vehicles. In recent years, much attention has been paid to this category of commercial vehicle trips. In metropolitan areas, goods movement trips, similar to longer-haul freight movements, are becoming a larger share of the total on-road vehicle load.

Finally, the services vehicles category includes household/building services such as plumbers and cleaning services as well as public safety, utility maintenance, and retail support functions. Due to the shift in the United States from a manufacturing-oriented economy to a service-oriented economy, the number of service-related commercial vehicle trips is growing faster than the number of trips for other purposes.

These three groups are further subdivided into 12 specific categories of commercial vehicles, based again on what is being carried and what economic, demographic and land use factors influence the magnitude and distribution of these trips. These 12 categories of commercial vehicles are direct subsets of the three commercial vehicle groups, as shown in Table 3.1.

One additional category of commercial vehicles is public and private buses. These vehicles were not evaluated in this study because some metropolitan transportation agencies already are modeling public and private buses as part of the multimodal demand forecasting process. These would be modeled as part of the development of the transit network; bus vehicle miles traveled can be estimated from the bus services coded in the transit network. Private buses are not as frequently modeled in urban transportation planning models, primarily because they are primarily intercity trips and would be modeled using an intercity or statewide model.