For some specific types of analysis, commercial vehicles can be organized into three groups based on what they transport and what economic, demographic, and land use factors influence the magnitude and distribution of commercial vehicle trips in a metropolitan area. The three groups of vehicles, along with the detailed set of commercial vehicle categories, are provided below:
Table 3.1 presents the percentage range of total VMT and VMT per vehicle per day by passenger, freight, and service vehicles for selected cities (Cambridge Systematics, November 2003). Of these three groups, service vehicles contribute the highest percentage of VMT, 5.9 percent (ranging from 1.4 percent to 12.7 percent). Freight vehicles are second, at 3.5 percent (ranging from 1.0 percent to 6.9 percent), followed by passenger vehicles at 2.4 percent (ranging from 1.0 percent to 5.4 percent). In terms of VMT per vehicle per day, passenger commercial vehicle trips are longer than freight and service vehicle trips.
| Vehicle Type | Range of VMT across Selected Urban Areas | VMT per Vehicle per Day | ||
|---|---|---|---|---|
| Minimum | Maximum | Average | ||
| Passenger | 1.0% | 5.4% | 2.4% | 66 miles |
| Freight | 1.0% | 6.9% | 3.5% | 50 miles |
| Service | 1.4% | 12.7% | 5.9% | 41 miles |
| Total | 3.4% | 25.0% | 11.8% | 48 miles |
Five of the 12 categories of commercial vehicles transport passengers:
About 2.4 percent of total vehicle miles traveled in urban areas in the United States each year are attributable to vehicles in these five categories. Rental cars, which make up 80 percent of vehicles in the commercial passenger group, account for fully 2.0 percent of total VMT in the United States, while school buses, taxis, and shuttle and paratransit services account for about 0.4 percent of VMT.
No specific urban transportation models include the "commercial passenger vehicle" as a separate trip purpose. However, several metropolitan planning organizations have attempted to include specific categories of these commercial vehicle in their models. The Las Vegas model is the only one that considers taxis as a separate mode in the mode choice model and assigns them to the highway network. The Tucson and Houston-Galveston models predict school bus travel, but do not assign or evaluate these trips. The San Francisco model includes mode choice for rental cars, taxis, and airport shuttles. The Portland model includes shuttle services and taxis in the mode and destination choice models. The Sacramento model includes airport trips as a separate trip purpose. In addition, a number of models deal separately with the development of trip tables for taxi trips (sometimes combined with 'truck' trips) and their assignment to the network using procedures akin to the Network-based Quick Response Methods presented in Section 2.0. Also, all urban models based on local survey data can be presumed to include rental cars used by residents with all trips made using privately owned passenger cars.
Very little research has focused on paratransit vehicles and no models have been developed to estimate the demand for these trips. Similarly, although rental cars contribute a significant percentage of VMT on U.S. roads, the project team could find no models that estimate the demand for rental cars specifically. A few visitor models (San Francisco, Honolulu, and Las Vegas) predict the mode share of auto trips, but the percentage of these trips attributable to rental cars is not considered.
To analyze the commercial passenger vehicle group, the project team created a dataset by combining data on school buses, shuttle services, rental cars, taxis, and paratransit vehicles. Data were derived from:
Data for four cities, Los Angeles, San Francisco, Detroit, and Portland (Oregon), were compiled and analyzed. Demographic data, including total population and total employment for each city, were derived from the 2000 Census.
The Aggregate Demand Method estimates fleet size, number of trips, and VMT based on total population and total employment. A summary of these travel behavior characteristics is provided in Table 3.2.
| Travel Behavior Category | Description of Methods | Estimates |
|---|---|---|
| Fleet Size | Fleet size can be estimated as a function of population. Data from Los Angeles, San Francisco, Detroit, and Portland (Oregon) were used to develop this factor. | 0.008 per total population (data from four cities). |
| Trip/Tour Length | Mileage for commercial passenger vehicles range from 149 miles per day for taxis to 18 miles per day for shuttle services. Group averages should take into account the weighted average of individual vehicle types in this category. | 58 average miles per day. |
| Trips | Daily trips per vehicle can be derived from DMV data. Data from the above four cities were analyzed. | Average 2.7 trips per vehicle (weighted average of school bus, rental car, taxi, paratransit and shuttle service vehicles). |
| Vehicle Miles Traveled | Passenger commercial vehicles represent a range of 1 to 5 percent of total VMT (Cambridge Systematics, November 2003) and 20 percent of the commercial vehicle VMT. | 2.4 percent of total VMT (based on data from 11 cities) |
Passenger trips is a function of population or employment. These trips are generally occurring at airports, hotels, tourist attractions, and businesses, so employment is used as a proxy for these generators, but employment in specific industries could provide a more direct link to these passenger trips. The project team estimated trip rates based on four cities. However, population and employment data for most of the cities are available from Census Data (United States Census Data, 2000) and trip rates can be estimated and passenger trips can be distributed using a gravity model with a friction curve borrowed from non-home-based trips. Since 80 percent of commercial passenger vehicles are rental cars, and 76 percent of rental cars are sedans (as opposed to pickup trucks or sport utility vehicles), more than 60 percent of commercial passenger vehicles are sedans.
Most commercial passenger vehicles operate during weekday business hours and the distribution among the time periods is probably fairly flat. Table 3.3 presents a summary of the travel behavior characteristics for commercial passenger vehicles using the Network-based Quick Response Method.
| Travel Behavior Category | Description |
|---|---|
| Trips/Tours | Cross-classification or regression models can be used with total employment or population. Data discussed in Section 2.2 were combined and a regression equation was developed for total daily trips. |
| Distribution | Passenger vehicles are distributed widely throughout the region and could be distributed with a gravity model. |
| Vehicle Type | Of total vehicles, 66 percent are car, 13 percent are bus, three percent are pickup, eight percent are SUV, seven percent are van, and three percent are other medium and heavy vehicles (DMV data). |
| Time of Day | Passenger vehicles operate primarily during weekday business hours and probably have a relatively uniform distribution during these hours. No data could be found on time of day for passenger vehicles. |
| Assignment | Passenger vehicles operate on all facilities. However, school buses operate mostly on local streets. |
Three of the 12 categories of commercial vehicles transport goods:
About 3.5 percent of the total vehicle miles traveled each year in urban areas in the United States are attributable to vehicles in these three categories. Urban freight vehicles alone contribute 2.7 percent of total urban area VMT, while package delivery and construction vehicles each contribute less than 0.2 percent. This category does NOT include the related movement of intercity freight to, from, or through urban areas, which is forecast using other techniques.
Urban transportation models typically include "commercial freight vehicles" in a goods movement model. Some of these goods movement models are vehicle-based truck models (Atlanta, Chicago, San Francisco, Buffalo, and Phoenix), some are commodity-based models (Portland) and some are hybrid models (Seattle and Los Angeles). These truck models include trucks from the commercial service vehicles category as well as intercity freight trucks traveling to, from or through an urban area. Most of these models identify trucks by weight class or type (light-, medium-, and heavy-duty) rather than by purpose (package delivery, urban freight, and construction).
To analyze the commercial freight group, the project team created a dataset combining data on package delivery, urban freight and construction vehicles.
The Aggregate Demand Method estimates fleet size, number of trips, and VMT based on total population and total employment. A summary of these travel behavior characteristics is provided in Table 3.4.
| Travel Behavior Category | Description | Estimates 1 |
|---|---|---|
| Fleet Size | Fleet size can be estimated as a function of population and employment. The presence of a major private or public distribution center will greatly impact the fleet size for the urban area. | 0.05 per total employment (data from four cities). |
| Trip/Tour Length | Mileage ranges from 43 to 66 miles per day by category and also is consistent across cities, with lower mileages in smaller cities. | Average mileage is 50 miles per vehicle per day or 11 average miles per trip (data from 11 cities). |
| Trips | Trips per vehicle can be derived from a commercial vehicle survey. | Average 4.6 daily weekday trips per vehicle. |
| Vehicle Miles Traveled | Freight commercial vehicles represent a range 1 to 7 percent of total VMT (Cambridge Systematics, November 2003) and 30 percent of commercial vehicle VMT. | 3.5 percent of total VMT (data from 11 cities). |
1 Estimates are based on commercial vehicle survey data from Atlanta, Denver, Detroit and the Triad cities.
All types of vehicles are used to move freight. Four-tire vans and light trucks are used primarily to pick up and deliver packages and to transport workers and their tools to and from construction sites. Commercial vehicles moving freight represent the vast majority of heavier commercial trucks in urban areas. Single unit, medium-sized trucks are used in the local delivery of urban freight and supplies to construction sites. Combination tractor trailer trucks are used to move heavy goods, and for trips to and from distribution centers. Fleet size is primarily a function of employment and population.
The number of trips for the commercial vehicle categories moving freight averages from four to five per vehicle per weekday day, based on available commercial vehicle surveys. However, it is assumed that for local delivery the definition of a "trip" is actually a chain consisting of many short-distance trips to homes, retail stores, or offices.
Commercial vehicle freight trips are a function of population or employment. Although the project team estimated trip rates based on data from four cities, population and employment data are available in the Task 3 Report for more than 300 cities. Using total commercial vehicle freight trips from available sources along with the Task 3 report data, trip rates can be estimated. Also, commercial freight trips can be distributed using a gravity model with a friction curve borrowed from non-home-based trips, as shown in Table 3.5.
| Travel Behavior Category | Description |
|---|---|
| Trips/Tours | Cross-classification or regression models can be used to predict daily trips attracted using total employment or population. There are 0.23 per total employment or 0.12 per total population (data from four cities). |
| Distribution | Commercial freight vehicles are distributed widely throughout the region and could be distributed with a gravity model. |
| Vehicle Type | Obtain results from registrations or commercial vehicle surveys. Estimates do not include public mail delivery vehicles because these were not included in the commercial vehicle surveys. Of commercial freight vehicles, 25 percent are four-tire trucks or vans, 59 percent are medium trucks, and 16 percent are heavy combination trucks. |
| Time of Day | Obtain results from commercial vehicle surveys. Of total trips, 50 percent occur during the midday period; 18 percent during the p.m. peak; five percent during the a.m. peak; and eight percent during the night (data from four commercial vehicle surveys). |
| Assignment | Freight vehicles operate on all facilities. However, some urban areas restrict the line-haul portion of the trip to certain streets. |
Trip generation rates for commercial vehicles moving freight are primarily based on the number of employees and persons in an urban area. Based on the data from the four cities, commercial vehicle productions can be estimated as 0.23 trips per employee and the corresponding attractions as 0.12 trips per person. While the attraction of trips for commercial vehicles moving freight can best be explained by the number of persons, these trips are usually not to homes, but to offices and retail stores whose location is highly correlated with population.
Trip distribution for commercial vehicles moving freight is highly concentrated in areas with high employment. While the package delivery category has a slightly shorter average mileage, there is little difference between the distribution and average mileage among the construction and the urban freight categories. The construction and package delivery categories average approximately 12.5 and 8.7 miles per trip, respectively. Urban freight averages 14.1 miles per trip based on commercial vehicle surveys. (Again, it is assumed that the definition of a "trip" is actually a chain consisting of many short trips to homes, retail stores, or offices.)
Commercial freight vehicles travel most frequently between 9:00 a.m. and 3:00 p.m., and to a lesser extent in the p.m. peak period. The percentage of daily commercial freight VMT in the average hour within the p.m. peak period is seven percent, compared to an average of 10 percent per hour during the midday hours. Travel is less frequent during the a.m. peak period (an average of two percent of the daily VMT per hour) and during the night (an average of one percent of the daily VMT per hour).
The assignment of commercial vehicles moving freight is permitted on the entire roadway system for travel in the vicinity of the establishments and homes they are serving. Some limitations based on vehicle size may apply for certain line-haul portions of travel removed from the origin or destination.
Four of the 12 commercial vehicle categories are vehicles providing services:
Public service vehicles are publicly owned. Business and personal service vehicles are privately owned. Safety and utility vehicles may be either publicly or privately owned.
About 5.9 percent of the total vehicle miles traveled in the urban areas in the United States each year is attributable to vehicles in these three categories. Business and personal service vehicles alone contribute 3.6 percent of the total VMT in urban areas across the nation, while public service vehicles contribute 1.6 percent of the total VMT and safety and utility vehicles contribute 0.4 percent each.
Urban transportation models currently do not include any commercial service vehicles specifically, although some models have identified a commercial vehicle trip purpose that is based on a fixed factor of personal non-home-based travel. Some truck models also include delivery and service vehicles that are four-tire commercial vehicles, based on the inclusion of these vehicles in the Quick Response Freight Manual (Cambridge Systematics, 1996).
To analyze the commercial services group, the project team created a dataset combining data on safety, utility, public service, and business and personal service vehicles.
Data for four cities, Los Angeles, San Francisco, San Diego, and Sacramento, were compiled and analyzed because these were the only four cities with a comprehensive assessment of all commercial service vehicles. Demographic data for each city, including total population and employment by type (government, utility, business and personal services and total), were derived from the 2000 Census.
The Aggregate Demand Method estimates service vehicle fleet size based on two demographic factors: total employment (possibly stratified by type) and population. A summary of the travel behavior characteristics is provided in Table 3.6. This summary includes estimates of fleet size, number of trips, and VMT calculated from a statistical analysis of the available data combined with demographic data. The only comprehensive data source (including both public and private sector data) is the motor vehicle registration data, so only these data are used in estimating rates of travel by commercial service vehicles. These data do not show trips per vehicle, so the commercial vehicle surveys are used to provide data on this variable for private sector vehicles only. The percent of vehicle miles traveled was estimated and presented in the Magnitude and Distribution of Commercial Vehicle Travel (Cambridge Systematics, November 2003).
| Travel Behavior Category | Description | Estimates |
|---|---|---|
| Fleet Size | Fleet size can be estimated as a function of population, based on data from the DMV. | 0.05 per population (data from four cities). |
| Trip/Tour Length | Average mileages are consistent across different cities and categories, ranging from 29 to 49 miles per day. National average miles traveled were derived from VIUS data. Average mileage was derived from commercial vehicle survey data. | 41 average miles traveled per day, average trip length is 14 miles (data from eight cities). |
| Trips | Trips per vehicle can be derived from a commercial vehicle and government vehicle survey. Trips per vehicle estimates were derived for private vehicles only from commercial vehicle surveys in Atlanta, Detroit, Denver, and the Triad cities. | Three daily trips per vehicle (data from four cities). |
| Vehicle Miles Traveled | Service vehicles range from five percent to 13 percent of total VMT for four cities (San Diego, Sacramento, San Francisco, and Los Angeles), based on DMV and VIUS data (Cambridge Systematics, November 2003) and represent 50 percent of total commercial vehicle VMT. | 5.9 percent of total VMT (data from four cities). |
Data on public and private service vehicles were available for only four cities: Los Angeles, San Francisco, San Diego, and Sacramento. No data was available for the number of vehicle trips or mileages for these four cities because the DMV data for those cities contains only fleet size. Data on vehicle trips and mileages are available from commercial vehicle surveys for private sector service vehicles for the cities of Atlanta, Denver, Detroit and the Triad cities. Additional data are necessary to more accurately evaluate travel behavior for all service vehicles. Table 3.7 presents a summary of the travel behavior characteristics for the Network-based Quick Response Method.
| Travel Behavior Category | Description |
|---|---|
| Trips/Tours | Cross-classification or regression models can be used with employment variables Government, utilities and business and personal services employment are the most likely variables. Trip rates are based on data from the DMV and the Bureau of the Census. There are 0.1 per total employment or 0.05 per population (data from four cities). |
| Distribution | All service vehicles are distributed widely throughout the region and could be distributed with a gravity model. National average miles traveled were derived from VIUS data. Average trip length was derived from commercial vehicle survey data. |
| Vehicle Type | Service vehicles are primarily light duty vehicles, dominated by public service, business, and personal service types (all light duty vehicles), based on data from the DMV. Some safety and utility vehicles are medium and heavy duty trucks (fire trucks, ambulances, utility trucks, etc.). Of commercial service vehicles, 91 percent are light duty vehicles and nine percent are medium/heavy duty trucks (based on data from four cities). |
| Time of Day | The majority of private service vehicles operate between 9:00 a.m. and 3:00 p.m., based on private service vehicles from the commercial vehicle surveys. The project team believes that the majority of public service vehicles also operate in this period. Of total trips, 11 percent occur in the a.m. peak, 23 percent in the p.m. peak, 53 percent in midday, and 14 percent at night (data from three cities). |
| Trip Assignment | Service vehicles operate on all facilities |
