Thomas Adler

A theoretical and empirical model of trip chaining behavior

This paper addresses the theoretical and empirical issues involved in modeling complex travel patterns. Existing models have the shortcoming of not representing the interdependencies among trip links in trip chains with multiple non-home stops. A theoretical model based on utility theory and explicitly accounting for the trade-offs involved in the choice of multiple-stop chains is developed. Using this theoretical model, utility maximizing conditions for a households choice of a daily travel pattern are derived. The optimum travel pattern is described in terms of the number of chairs (tours) traveled on a given day and in terms of the number of stops (sojourns) made on each of those chains. For a given household, the form of the optimum pattern is a function of the transportation expenditures (time, cost) required to reach potential destinations. Constraints on the conditions of optimality due to the limited and discrete nature of travel pattern alternatives are also considered. Parameters of the general utility function were estimated empirically using actual travel data derived from a home interview survey taken in Washington, D.C. The multinomial logit model is used to relate utility scores for the alternative travel patterns to choice probabilities. The resulting parameter estimates agree with theoretical expectations and with empirical results obtained in other studies. In order to demonstrate the empirical and theoretical implications of the model, forecasts for various transportation policies (e.g., gasoline price increases, transit fare reductions), as made by this model and by other less complex models, are compared. The results of these comparisons indicate the need for expanding the scope of existing travel forecasting models to explicit considerations of trip chaining behavior.

Modeling Service Trade-Offs in Air Itinerary Choices

The application of a mixed logit approach using stated-preference survey data to the development of itinerary choice models is described. The models include the effects on itinerary choices of airline, airport, aircraft type, fare, access time, flight time, scheduled arrival time, and on-time performance. The empirical results demonstrate the importance of explicitly accounting for traveler preference heterogeneities by using segmentation by trip purpose, interaction effects involving frequent flier status, and random parameter specifications. Explicitly including preference heterogeneity by using the mixed logit specification results in significant statistical improvements and important coefficient differences as compared with using a standard fixed-parameter logit model. The calculated marginal rates of substitution show the relative importance that travelers assign to key service variations among itineraries. All service features that were included in the model had significant values to travelers, and ...

Risk Aversion to Short Connections in Airline Itinerary Choice

Network airlines traditionally attempt to minimize passenger connecting times at hub airports, assuming that passengers prefer minimum scheduled elapsed times for their trips. However, minimizing connecting times creates schedule peaks at hub airports. These peaks are extremely cost-intensive in terms of additional personnel, resources, runway capacity, and schedule recovery. Consequently, passenger connecting times should be minimized only if the anticipated revenue gain of minimizing passenger connecting times is larger than the increase in operating cost (i.e., if this policy increases overall operating profit). The extent to which a change in elapsed time affects passenger itinerary choice—and thus an airlines market share—is analyzed. An existing airline itinerary choice survey is extended to test the assumption that passenger demand is affected by the length of connecting times. Previous studies have not explicitly focused on the connecting time at hubs in their models. The hypothesis is that passe...

Use of Internet-Based Household Travel Diary Survey Instrument

The results of an application of Internet survey methods to a household travel diary project are described. The project included a full field application of an Internet-based household travel diary instrument in a split sample design with conventional telephone or mail administration. The effects of this type of administration on survey response and on survey data are described. The work described demonstrates how Internet-based travel diary instruments can be used to complement other, more traditional survey approaches. The Internet household travel diary instrument used included several features that take advantage of the computational power provided by modern servers and the graphical user interface provided by web browsers. Among these, the most important are detailed internal consistency checks that test the continuity and completeness of the activity and trip logs and interactive geocoding of trip ends. The response rates in the split sample conducted for the Las Cruces application indicate that providing an Internet option had a small positive effect. However, there are more pronounced effects on reported trip making—more trips reported in the Internet instrument—and on item nonresponse—lower rates with the Internet instrument. Overall, respondents who used the Internet instrument found it easy to use and appreciated having the option to complete the questionnaire at their convenience. There are clear areas for further research, but it is equally clear that Internet-based household diary surveys can provide an important, cost-effective complement to computer-assisted telephone interview and mail methods.

Design of comprehensive microsimulator of household vehicle fleet composition, utilization, and evolution

This paper describes a comprehensive vehicle fleet composition, utilization, and evolution simulator that can be used to forecast household vehicle ownership and mileage by type of vehicle over time. The components of the simulator are developed in this research effort by using detailed revealed and stated preference data on household vehicle fleet composition, utilization, and planned transactions collected for a large sample of households in California. Results of the model development effort show that the simulator holds promise as a tool for simulating vehicular choice processes in the context of activity-based travel microsimulation model systems.

Improving the quality of demand forecasts through cross nested logit: a stated choice case study of airport, airline and access mode choice

Airport choice models have been used extensively in recent years to assist the transport planning in large metropolitan areas. However, these studies have typically focussed solely on airports within a given metropolitan area, at a time when passengers are increasingly willing to travel further to access airports. This article presents the findings of a study that uses broader, regional data from the East Coast of the United States collected through a stated choice based air travel survey. The study makes use of a cross-nested logit structure that allows for the joint representation of inter-alternative correlation along the three choice dimensions of airport, airline and access mode choice. The analysis not only shows significant gains in model fit when moving to this more advanced nesting structure, but the more appropriate cross-elasticity assumptions also lead to more intuitively correct substitution patterns in forecasting examples.

Generating Route-Specific Origin–Destination Tables Using Bluetooth Technology

Bluetooth media access control (MAC) data collection technology has emerged as a forerunner in the suite of passive data collection techniques used in travel time and origin–destination (O-D) data collection efforts because of its low cost, ease of implementation, and richness of the resultant data set. With a few notable exceptions, the majority of published research and practical applications of Bluetooth MAC data to date have focused on travel speed analysis. This paper aims to add to the existing literature on Bluetooth O-D data research by describing an analytic approach used to develop route-specific O-D tables for a 15-mi corridor in Jacksonville, Florida. The data from this project were successfully used as an after-model validation tool for base and future year toll revenue forecasts. Bluetooth MAC data were shown to provide a robust and rich data set capable of providing insight into the travel patterns of users in a corridor that would not be easily or efficiently achieved with other data collection methods. The paper also seeks to provide practical guidance and insight into successfully deploying and analyzing Bluetooth MAC data.

Joint Vehicle Holdings, by Type and Vintage, and Primary Driver Assignment Model with Application for California

In this paper an estimation is made of a joint household-level model of the number of vehicles owned by a household, the vehicle type choice of each vehicle, the annual mileage on each vehicle, and the individual assigned as the primary driver for each vehicle. A version of the proposed model system currently serves as the engine for a household vehicle composition and evolution simulator, which itself has been embedded in the larger Simulator of Activities, Greenhouse Emissions, Energy, Networks, and Travel (SimAGENT), an activity-based travel and emissions forecasting system for the Southern California Association of Governments planning region.

Customer Perspectives on Multilevel Coaches for Increasing Rail System Capacity

The numbers and lengths of New Jersey Transit (NJT) commuter trains accessing New York’s Penn Station are currently at the limits of available capacity during peak periods, as evidenced by the significant number of standees at these times. NJT is planning to purchase multilevel coaches to address this critical passenger capacity issue. A study was conducted to determine the design of these multilevel coaches so that they will provide the extra capacity needed and also reflect customers’ preferences. The study focused on interior issues, including the seating configuration and seat design, that relate directly to the amount of seated (and standee) capacity on the new coaches. A two-part research approach was used to obtain customer input. First, focus groups and product clinics were conducted to get qualitative feedback on the multilevel coach concepts and on specific seat designs. A detailed, computer-based survey was administered to customers to quantify their preferences among key elements of the multilevel concepts, and to estimate their willingness to pay for those elements. The study found that additional seating capacity in the configuration preferred by customers provides a substantial net benefit to NJT passengers, equivalent to about

Traveler reactions to congestion pricing concepts for New York's Tappan Zee Bridge

2.20 fare value per trip. The benefits are higher for this application because of the crowded conditions on existing trains. The study also suggests that multilevel coaches and improved interior design have benefits well beyond increased capacity.