Research Projects

Patricia L. Mokhtarian, Principal Investigator

U. S. Department of Transportation Region Nine Transportation Center. Is Accessibility the Solution for All? Segmenting the Market for Mobility and Accessibility Policies. August 1997 - July 1998.

Improvements in accessibility are increasingly suggested as strategies leading to a reduction in vehicular travel, congestion and their related impacts. This approach assumes that individuals, if offered an opportunity, are likely to reduce their travel. It also assumes that such land-use changes will increase non-motorized trips in lieu of automobile usage. However, there are numerous indications that people engage in excess travel and are not necessarily inclined to reduce it. The proposed study will test a number of hypotheses on the reasons for excess travel and the relationships among attitudes toward travel and responses to accessibility-enhancing strategies. It will investigate these relationships across different travel categories (work, maintenance and discretionary). The study assumes that different market segments exhibit different relationships and hence are likely to respond to policy measures in different ways. It is suggested that if a large segment of the population prefers mobility over the reduced travel offered by accessibility improvements, then such policies will be less effective than anticipated. The analysis will be based on data collected for this purpose in two or more communities in a metropolitan area of California.

Partners for Advanced Transit and Highways. Beyond Telecommuting: The Travel/Communications Impacts of Advanced Telecommunications Services. September 1996 - July 1997.

The travel impacts of telecommunications applications such as telecommuting have been the subject of several studies to date; other applications have received considerably less attention. To our knowledge there are no other studies of the travel impacts of recently-developed applications such as community networks and other on-line information- and transaction-oriented services - the subject of this proposal. These services can provide information about activity opportunities as well as about the transportation system, and as such may generate or modify travel as well as replace it. It is important to learn much more than we now know about how the activity and transportation information provided by these services will affect demand, with its consequent effects on network performance. Thus, the proposed project represents a valuable extension of existing ITS research into the impacts of transportation system provision (such as real-time congestion information or carpool formation opportunities) on the demand for travel.

This project will examine the behavioral impacts of telecommunications-based information/ transaction services. Part of the project continues the analysis of data collected under the Davis Community Network (DCN) Project funded by Caltrans. These unique data were collected from multiple, complementary instruments, including before and after logs of communications activities over a four-consecutive-day period, an activity diary which records information on likely impacts of specific uses of the DCN system, system utilization statistics, and a background demographic survey. In addition, the project will gather information on existing and planned traveler information systems, and examine policy issues relevant to the questions of adoption and travel impacts of such systems.

This exploratory study will lead to refinements in our conceptual and methodological approach to understanding the impacts of similar telecommunications systems. Further, it will inform the policy question of whether (and if so, how) such systems should be promoted as congestion management measures.

Researchers: Ravikumar Meenakshisundaram and Ilan Salomon

Partners for Advanced Transit and Highways. Is there a Case for Public Investment in Telecommuting? The Cost/Benefit Analysis. (Co-PI with Debbie Niemeier). September 1996 - July 1997.

While much has been learned to date about the specific transportation impacts of small-scale telecommuting projects, important questions about the degree to which telecommuting is a cost-effective transportation policy remain unanswered. The proposed project would redress that deficiency by conducting a formal economic evaluation of telecommuting and assessing the resulting transportation policy implications. The study will assess the costs and benefits of home-based telecommuting, develop a suitable framework for the future economic analysis of telecommuting, and offer policy guidance on the conditions under which benefits may be optimized. The information provided by such a study is fundamental to proper placement of telecommuting on the public policy agenda, and has been notably lacking from telecommuting research and policy discussion to date. The methodology developed for this project will also be highly relevant to the assessment of the cost-effectiveness of other ITS strategies.

The proposed research involves first, a review of relevant cost-benefit and telecommuting literature. This review will identify the important components of costs and benefits, and the pros and cons of different economic analysis methodologies. Specific scenarios of home-based telecommuting adoption will be developed, from both public- and private-sector perspectives. A base case of background conditions (such as traffic levels) and their evolution over time will be developed. The costs and benefits of each specific telecommuting scenario - to the public sector, the employer, and the individual - will be measured. Primary and secondary data will be used to estimate the specific costs and benefits of the selected scenarios over the project life. This project will explore a novel methodological approach to the measurement and valuation of qualitative benefits (particularly to the individual), through the use of attitudinal factor scores and logit models of choice developed in a previous study. Alternative evaluation techniques such as net present value and benefit/cost ratio will be analyzed and the most appropriate one(s) selected. Sensitivity analysis will be conducted on key inputs and assumptions. The policy implications of the empirical findings will be examined, and recommendations made.

Researchers: Kevan Shafizadeh and Ilan Salomon

U. S. Department of Transportation Region Nine Transportation Center. Behavioral Adjustments to Congestion. August 1995 - July 1996.

An understanding of how individuals perceive and respond to congestion is crucial for the development of relevant, effective policies for dealing with congestion. This study is empirically testing two hypotheses: that responses to congestion are a function of previously-adopted adjustments, and that responses are distributed differently across various socio-economic segments. Findings to date support both hypotheses. Eighteen coping strategies have been classified into 3 tiers: lower-effort strategies (such as changing departure time or buying a better car stereo) which increase the comfort of maintaining existing travel; moderate-effort strategies (such as changing commute mode or telecommuting) which tend to reduce travel; and major lifestyle/location change strategies such as job or residence changes. Lower-effort strategies tend to be adopted first, with higher-effort strategies adopted if dissatisfaction persists. Women (particularly those with children at home) are more likely than men to have adopted or considered the more costly strategies.

Researchers: Liz Raney and Ilan Salomon

U. S. Department of Transportation Region Nine Transportation Center. An Empirical Analysis of the Travel Behavior of Telecommuters and Home-Based Business Owners. August 1994 - July 1995.

This work in progress is using two complementary travel diary data bases: the Puget Sound Telecommuting Demonstration Project data, and the 1991 Caltrans Statewide Origin-Destination Survey data. Travel characteristics (VMT, number of trips, mode choice, trip purpose and time-of-day distributions) are being compared across four groups: (1) home-based telecommuters, (2) home-based business workers, (3) center-based telecommuters, and (4) conventional workers. Groups 1, 3, and 4 are present in the first data base, and groups 1, 2, and 4 are identifiable in the second data base. This study will constitute the first known analysis of the travel behavior of groups 2 and 3.

Researcher: Dennis Henderson
Publications: TRP21, TRP22

Washington State Energy Office. Puget Sound Telecommuting Demonstration Transportation Emissions Analysis. June 1994.

An analysis of the emissions impacts of telecommuting was conducted using travel diary data from telecommuters and non-telecommuters in the Puget Sound area. Characteristics of individual vehicles and trips and region-specific temperature data were used as input to the California Air Resources Board's EMFAC/BURDEN 7F models. This and a similar study described below represent novel applications using EMFAC and BURDEN with travel diary data to evaluate a specific transportation control measure (as opposed to the more conventional use of these models to estimate regional emission inventories).

Researchers: Dennis Henderson and Brett Koenig
Publications: TRP19, R9

U. S. Department of Transportation Region Nine Transportation Center. Market Segmentation of the Demand for Telecommuting. August 1993 - July 1994.

This is a continuation of the study titled "Modeling the Choice to Telecommute", described below. In this extension, additional models of preference and choice are being developed; in particular the preference specifically for telecommuting centers is being modeled. Several market segmentation questions are being explored, including potential gender and occupational differences in the perceived advantages of telecommuting, and identification of clusters of people with similar types of drives (e.g., predominantly work-driven, predominantly family-driven, and so on).

Researcher: Michael Bagley
Publications: TRP23, R10

California Energy Commission. Present Status and Future Directions of Telecommuting in California. November 1992 - September 1993.

This study provided input to the CEC's forecasts of future statewide energy consumption. The current (1991) aggregate level of telecommuting in California was estimated from a variety of national, state, and regional sources. Transportation-related impacts of the current level of telecommuting were estimated through a synthesis of a number of published empirical studies. Future levels of telecommuting and its transportation impacts were estimated under the assumed continuation of present trends. Factors and policies likely to affect future levels of telecommuting were described, and suggestions for incorporating telecommuting into regional and statewide transportation and energy models were made.

Researcher: Dr. Susan Handy
Publications: TRP11, TRP12, TRP17, TRP18, R3, R4, R5, R6

California Department of Transportation (Caltrans). Residential Area-Based Telecommuting Work Centers. July 1992 - January 1997.

A number of studies have now demonstrated the transportation-related benefits of home-based telecommuting. But for a variety of reasons, telecommuting centers may be a preferred form of telecommuting for some employees or employers. It is important to analyze the effectiveness of telecommuting centers both as a travel reduction strategy and as an alternative work arrangement. This project involves opening and evaluating 12 telecommuting centers in metropolitan areas of the state. The centers are located in or near residential areas so as to maximize the potential for eliminating vehicle commute trips. Before and after travel and attitudinal information is being collected from center-based telecommuters, and from home-based and non-telecommuting control groups. Before and after attitudinal information is being collected from managers of the employees in each of these groups. Data on center description, operation, funding, marketing, and occupancy are also being collected.

Administrative Staff: Carol Buckinger, Michelle Derr, and Francisca Mar
Researchers: Prashant Balepur, Sally Ho, David Stanek, and Krishna Varma
Publications: TRP25, R8, R11

California Department of Transportation (Caltrans). Davis Community Network Demonstration Project. July 1992 - June 1995.

This project is intended to evaluate the transportation and communications impacts of providing advanced telecommunications services to homes and businesses in Davis. These services could result in (1) the substitution of trips or other communications (e.g. the replacement of paper mail with electronic mail), (2) generation of new trips or communications, and/or (3) modification of existing travel or communications (e.g. changing mode in response to the provision of real-time transit system information). Original data collection instruments have been developed, and before and after data are being collected to quantitatively and qualitatively assess the degree to which each of these outcomes occurs.

Researchers: Dr. Prasuna Reddy, Prashant Balepur, and Krishna Varma (formerly Dr. Susan Handy, Michael Bagley, and David Stanek)
Publication: R7

U. S. Department of Transportation Region Nine Transportation Center. Modeling the Choice to Telecommute. August 1991 - July 1992; August 1992 - July 1993.

This project was designed to achieve greater understanding of an individual's choice to telecommute or not, to provide a behavioral foundation for forecasts of future levels of telecommuting. A conceptual model of the individual's decision process was developed, involving the identification of constraints or facilitators that (respectively) inhibit or support telecommuting, and drives or motivations to telecommute. Most people currently do not have the choice to telecommute, due to one or more constraints such as management unwillingness or job unsuitability. However, removal of constraints is only a necessary but not sufficient condition for telecommuting to be adopted; it is also necessary that one or more drives be active. A questionnaire was designed to obtain data on the identified drives and constraints, and was administered to a sample of more than 800 people in three organizations. These data permit analysis of the extent to which various constraints are active, and the development of quantitativ e models of the preference for and choice of telecommuting.

Researchers: Prof. Ilan Salomon and Michael Bagley (formerly Laura Laidet and Jill Mannering)
Publications: TRP8, TRP13, TRP14, TRP15, TRP16, TRP20, NRP9

P. L. Mokhtarian, Co-Principal Investigator

A number of studies have shown an associative relationship between land use and travel behavior. Specifically, low-density single-purpose land uses and low levels of transit service tend to be associated with greater numbers of vehicle-trips and more vehicle-miles traveled. It is tempting then to draw the conclusion that a land use policy promoting greater densities, mixed uses, and higher transit levels of service will be an effective strategy in reducing the demand for vehicular travel. However, evidence of the direction of causality, or even the existence of causality at all, has not been obtained. For example, do people make fewer trips because they live in higher-density neighborhoods, or do they live in higher-density areas because they prefer to make fewer trips? If the latter situation is the case, then putting a different type of person into a high-density development may not have the desired effect on travel. This study makes a contribution to this complex issue by examining the role of attitu des in travel behavior. Travel diary, attitudinal/lifestyle, land use, and socioeconomic data were collected for respondents in five diverse neighborhoods in the San Francisco Bay Area. Regression models of trip-making behavior (total number of trips, number of auto trips, and so on) were developed with socioeconomic, land use, and attitudinal explanatory variables. The attitudinal variables (including orientations toward various residential and travel lifestyles) contributed significant explanatory power to the models, suggesting that they have a stronger and more direct link to travel behavior than objective characteristics alone.

Researchers: Carol Buckinger, Fred Gianelli, Laura Laidet, and Francisca Mar
Publication: ORP3

U. S. Department of Transportation Region Nine Transportation Center. Impact of Telecommuting on Travel: Accessibility Implication of Working at Home. August 1990 - July 1991 (co-PI with R. Kitamura, P. P. Jovanis, and D. S. Bunch).

This project focused on changes in non-work travel-related behavior due to telecommuting. The travel diary data from the State of California Telecommuting Demonstration Project were geo-coded (latitudes and longitudes of recorded locations were identified and appended to the file) and used to analyze changes in the spatial distribution of activity locations. Models of time spent in-home versus out-of-home were also developed.

Researchers: Kostas Goulias, Ram Pendyala, Srikanth Sampath, and Somitra Saxena.
Publications: TRP24, NRP4

University of California Energy Research Group. Telecommuting, Energy and Air Quality. July 1990 - June 1991 (co-PI with R. Kitamura and P. P. Jovanis).

The energy and air quality impacts of telecommuting were evaluated for the State of California Telecommuting Demonstration Project. Travel diary data were collected before and after telecommuting began, from telecommuters, a non-telecommuting comparison control group, and driving-age household members of both groups. From these "person" diaries, "vehicle" diaries were prepared that tracked movement of individual household vehicles across the three-day travel diary period. Only in this way could a specific vehicle trip be confidently identified as a hot start or a cold start. Sample-specific data on vehicle types and trip-making activity were developed and input to the California Air Resources Board's EMFAC/BURDEN 7E models to quantify emission levels associated with the travel behavior of the sample. This constitutes the first known integration of travel diary data input to emissions inventory models in order to evaluate the impact of a specific transportation control measure.

Researchers: Srikanth Sampath and Somitra Saxena
Publication: TRP5