Nationwide Personal Transportation Survey Data Research Articles

Transferability of Nationwide Personal Transportation Survey Data to Regional and Local Scales

The development of a system for using Nationwide Personal Transportation Survey (NPTS) data to estimate regional or local travel behavior—vehicle and person trips and miles of travel—is detailed. This system can be used by state or municipal transportation planners. The census tracts were classified into groups, or clusters, that tend to be homogeneous for individual travel behavior. These census tract clusters were based on household income, employment rate, number of household vehicles, and area type (urban, suburban, or rural). NPTS data were used to estimate driving characteristics for each of the clusters derived in the classification step. How well the goal of estimating regional or local travel characteristics was achieved by using standards computed from an independent survey from Baton Rouge, Louisiana, and by using independent data from three add-on components of the NPTS itself was assessed. Estimates computed from the NPTS data by using the census tract cluster method were compared with estimates computed from the standards and with estimates computed from the NPTS data by using competing methods in which households were classified by size of the metropolitan statistical area, census division, or census region. It was found that in most cases the census tract clustering method predicted travel better than the other methods, with small sample sizes generally being the cause when the census tract method was not the best.

Soak Distribution Inputs to Mobile Source Emissions Modeling: Measurement and Transferability

Soak period distribution is a key input for modeling the emissions factors for mobile sources. Methods for deriving soak period distributions from travel survey data are discussed. Data from the 1995 Nationwide Personal Transportation Survey (NPTS) were analyzed to derive soak times. Detailed analyses were conducted to relate soak time variability to geographic, trip-purpose, and time-of-day variables. The findings reinforce the prevailing general guidance on inputs to modeling the emissions from mobile sources. That is, whenever possible, local data should be used to derive soak distribution inputs to the emissions models. Alternatives are offered to accurate but more expensive local surveys as well as to the roughly aggregate and potentially inaccurate national defaults on soak period inputs to emissions factor models such as MOBILE6. On the basis of a detailed statistical analysis, a grouping scheme is devised to consolidate soak distribution inputs by time period. The grouping scheme will enhance the utility of survey data in deriving the soak distributions and reduce the effort in providing soak distribution inputs to MOBILE6. The soak periods derived from the NPTS data also can be used for deriving the operating-mode fractions inputs needed for MOBILE5B and modal emissions models.

Mixed Generalized Linear Model for Estimating Household Trip Production

An innovative modeling framework to estimate household trip rates using 1995 Nationwide Personal Transportation Survey data is presented. A generalized linear model with a mixture of negative binomial probability distribution functions was developed on the basis of characteristics observed from the empirical distribution of household daily trips. This model provides a more flexible framework and a better model specification for analyzing household-specific trip production behavior. Compared with traditional least squares-based regression models, the parameter estimates from the proposed model are more efficient. Although the mean accuracies from the two modeling approaches are comparable, the mixed generalized linear model is more robust in identifying outliers due to its unsymmetric prediction bounds derived from more correct model specification.

Testing for the Significance of Induced Highway Travel Demand in Metropolitan Areas

A research study was conducted to evaluate and quantify the effect of highway capacity improvements on travel demand. Statistical models using Nationwide Personal Transportation Survey data were designed to estimate relationships between average household travel time and vehicle-miles of travel. Several regression models were estimated, and the results were stratified by urbanized area, public transportation availability, metropolitan area size, family life cycle, day-of-week of travel, and population density. Travel-time elasticities of -0.3 to -0.5 were generally found, after taking into account the effects of household size, income, population density, and household employment. These results suggest that travelers will spend 30 to 50 percent of the time savings afforded by highway improvements in additional travel. Overall, the results of this study provide evidence that highway capacity improvements can create additional travel, although the magnitude of the induced traffic effect was found to be smaller than that reported by some previous researchers.

Trip Linkage Patterns for Workers

This study examines the trip-chaining behavior of workers. It develops nine work-related trip-chaining patterns from the 1990 Nationwide Personal Transportation Survey data, based on the sequential link of activities occurring in a single day. The study finds that more than 60% of trips for work in urban areas represent complex trip-chaining patterns. Males are more likely to use a simpler work trip pattern than females. From the results of analysis of variance, there are gender variations between trip-chaining patterns in trip rates for nonwork activities, travel distance, and travel time. There are also significant gender differences in trip rates and travel resources in each trip-chaining pattern.

A note on the travel speeds debate

This note challenges the use of census data for evaluating changes in commuting speeds, partly because these data require indirect distance measures, but primarily because they do not differentiate between non-stop trips and trip chains. The proportion of trip chains to total trips increased between 1983 and 1990 (Nationwide Personal Transportation Survey). Hence, results of declining speeds based on census data may be spurious. When trips are broken down by type using Nationwide Personal Transportation Survey data, speeds increased between 1983 and 1990 for all categories, in all but one of eight cases studied, by significant amounts.

Using Nationwide Personal Transportation Survey Data to Indicate Electric Vehicle Market Potential in Rural Areas

The 1990 Nationwide Personal Transportation Survey included 10,381 rural households, that is, households that were not in metropolitan statistical areas and were in zip code areas with population densities of less than 386 persons/km2 (1,000 persons/mi2). An analysis of the survey data to determine how rural households use their household (nonfarm) vehicles and to describe the potential for some vehicles to be electric vehicles (EVs) is reported. A main step in the analysis is to aggregate the daily household trips by vehicle. The counterintuitive result is that rural household vehicle use in terms of kilometers per day is quite similar to that of metropolitan area households. Thus, the potential for rural households to acquire EVs is similar to that for metropolitan area households.

Using Nationwide Personal Transportation Survey Data To Indicate Electric Vehicle Market Potential in Rural Areas

The 1990 Nationwide Personal Transportation Survey included 10,381 rural households, that is, households that were not in metropolitan statistical areas and were in zip code areas with population densities of less than 386 persons/km2 (1,000 persons/mi2). An analysis of the survey data to determine how rural households use their household (nonfarm) vehicles and to describe the potential for some vehicles to be electric vehicles (EVs) is reported. A main step in the analysis is to aggregate the daily household trips by vehicle. The counterintuitive result is that rural household vehicle use in terms of kilometers per day is quite similar to that of metropolitan area households. Thus, the potential for rural households to acquire EVs is similar to that for metropolitan area households.

Impact of Technological Developments on Urban Form and Travel Behaviour

KUMAR A. (1990) Impact of technological developments on urban form and travel behaviour, Reg. Studies 24, 137–148. The growth and diffusion of new information technologies in cities are transforming the structural and spatial relationships between the residence and the workplace with a significant impact on commuting behaviour. This paper uses the Nationwide Personal Transportation Survey data for the years 1977 and 1983–84 to analyse the changes in two basic travel parameters over the six-year period: worktrip distance, representing the degree of dispersal of urban activity; and worktrip frequency, representing the intensity of linkages between the labour force and economic activities. The analysis supports the hypothesis of a dispersal of information-dominated activities as revealed by declining commuting distances. In addition, the possibility of ‘telecommuting’ to work from home and decentralized work stations is becoming a reality for some people in certain occupations. An econometric model is tested...