There are three primary types of data sources that can be used to support new methods for estimating commercial vehicles in urban transportation models: travel surveys, other types of surveys and geographic information systems (GIS) data. The data sources discovered during the course of the literature review are discussed in this section. This is not necessarily comprehensive of all possible data sources, but intended to identify the types of data sources that would be available.
The 1995 National Personal Transportation Survey (NPTS) (http://npts.ornl.gov/npts/1995/Doc/publications.shtml) and the new 2000 National Household Travel Survey (NHTS) (https://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/subject_areas/national_household_travel_survey/index.html) are potential sources of information on certain kinds of commercial vehicles. The 1995 NPTS contains the following modes, which may be relevant to this study:
The use of pickup and other trucks would be in combination with other information on trip purpose to identify whether these were used for commercial purposes.
The ITE Trip Generation Manual (ITE, 1997) contains vehicle trip rates for a number of land uses that may be relevant for this study:
This manual reports on the vehicle trip rates per employee (or other size variable), so use of these data would require a separate estimation of employee work trips in personal vehicles to identify the commercial vehicles portion of the total vehicle trips.
There have been a number of regional commercial vehicle surveys that may provide data for this study (Denver, Houston-Galveston, Piedmont Triad, Los Angeles, Atlanta, Detroit, Portland, and El Paso). Our review of these surveys identified the need to obtain the actual data for evaluation, since the relevant information on specific vehicles was not necessarily available through documentation. The survey data were collected either through a survey of businesses that operate commercial vehicles (also referred to as shippers and carrier surveys) or by identifying commercial vehicles through registration records. There is one study (Lawson et al., 2001) that compares different types of data collection methods for shippers and carriers and determines the effectiveness of the different methods.
There have also been travel surveys to collect data on vanpooling in Seattle and Chicago. In Seattle (Cambridge Systematics, 2002), travel surveys on existing vanpooling trips and inventories of the vanpool services were used to evaluate the vanpool market. In Chicago (Koppelman et al., 2002), stated preference surveys of travelers were collected to determine the effect of proposed vanpool services on vanpool propensity.
There are a number of other types of surveys that we discovered during the literature review that are relevant to different types of commercial vehicles. In Washington State (Nee et al., 2001), the Department of Transportation conducted a survey of 5,000 tow trucks to determine response times and types of incidents in the region. The original survey data on incident response and additional data on feedback to the survey are available from the WSDOT.
In St. Louis, the East-West Gateway Coordinating Council (1996) conducted a survey of paratransit operators to collect data on trip purpose, service area, service hours, unused vehicle miles, operating and capital budgets, and other information. In addition, 431 vehicles were surveyed to estimate trips per vehicle.
There is a national organization of school bus fleets that conducts a survey of school districts and school bus contractors every year (http://www.schoolbusfleet.com/t_inside.cfm?action=research#State-by-State%20Transportation%20Statistics). The survey collects data on bus fleet size and passenger loads for the top 100 school districts and the top 50 school bus contractors in the United States. The surveys are also used to estimate the total route mileage of school buses for each state.
There is a long list of potential GIS data sources that could provide useful information for the evaluation of commercial vehicles in urban transportation models. The most relevant publicly available sources are listed below:
There are also a number of commercially available data sources, a few of which are listed below:
Most commercial vendors place restrictions on the use of their digital data sets beyond in-house purposes. This includes publishing of the data on the internet.
The Geographic Information System (GIS) and Global Positioning System (GPS) are complementary technologies that help to expand potential applications related to commercial vehicle tracking and routing. Emergency medical services, police patrols, armored trucks, dial-a-ride public transit services, school bus routing, taxi cabs and limos, airport shuttle as well as express deliveries can all take advantage of GIS and GPS technology for cost-effective fleet monitoring and dispatch. GIS data are mostly likely available from dispatch centers for the above services.
The following related GIS data can be obtained from public sources for the use of this study. ESRI has released 2000 Tiger layers of school districts for elementary, middle, secondary, and unified boundaries. These are polygon shapefiles covering the whole nation. The integration of school district boundary files with information regarding bus routes, schedules, events, school locations can be highly useful for school bus trip studies. There is also a NTAD Public Use Airport GIS layer for the locations of all public airports in the nation, 2001. It can be used for airport shuttle service studies. There are also various GIS utility layers available for Pipelines, Water Supply, Sewers, Storm Drains, Utility Lines, Electric Power Industry throughout the whole nation. Local GIS coverages can be obtained from state or county GIS data clearance centers. For example, the Wake County of North Carolina published their Fire District Police Stations GIS layers in 2001.
