The purpose of the literature review was to assess recent and current literature relevant to the treatment of commercial vehicles in urban transportation models. This literature review includes published literature, unpublished literature, information from the Internet, GIS and survey data sources and internal project documents on related topics.
To date, most of the literature on this topic revolves around urban freight distribution. The state-of-the-practice in the modeling of commercial vehicle travel in the urban transportation context has been geared toward developing a limited number of commercial vehicle trip generation factors, typically only disaggregated by truck type; for example, light, medium and heavy trucks. The traditional approach of relating these rates to land use activity has been found to be limited for application in travel demand modeling due to lack of data on differences in trip purpose, vehicle occupancy, and origin-destination (O-D) patterns. Other definitions of commercial vehicles rely on vehicle registration classifications.
To clarify the scope of the literature review, 13 categories of commercial vehicles were defined and included both individually and categorically in the literature review (these 13 categories were later modified and reduced to 12 categories, as described in Section 3.0). Initial reviews on commercial vehicles in general uncovered very few sources in the literature, so the majority of the literature review was focused on individual vehicle types.
In addition, the literature review was focused on trips within an urban area (intraregional trips) rather than on trips entering or leaving an urban area (interregional trips). This is a critical distinction for urban freight trips, where much of the current literature covers interregional freight distribution rather than intraregional freight distribution. This distinction is expected to carry forward in the development of methods for estimating commercial vehicle traffic, where the interregional traffic is estimated using different techniques related to external traffic than intraregional traffic, which is estimated using more specific methods related to trip purpose, demographics and other characteristics of the region.
The literature review provided an overview of the information found on state-of-the-practice techniques, on data sources, and on modeling approaches. The report also provided more detailed information on the individual literature reviews for each commercial vehicle type. The detailed summary of the literature review for individual references addressed the following questions:
