Jennifer Dill's Research

Examine the relationship between community environmental factors and people's decision to bicycle, including network connectivity, bicycle infrastructure, and land use;
Examine other intervening factors influencing the decision to bicycle, such as weather, topography, attitudes and perceptions of subjective and objective factors, and socio-demographics; and
Test the use of readily available technology to objectively measure physical activity of bicyclists.

Some surveys indicate that providing bicycle lanes and paths may encourage more people to commute by bicycle. The presence of a striped lane or separated path can increase a cyclist's perception of safety. With growing concerns over traffic congestion and vehicle pollution, public policy makers are increasingly promoting bicycling as an alternative for commuting and other utilitarian trip purposes. States and local spending on bicycle facilities has increased significantly over the past decade. Previous studies have linked higher levels of bicycle commuting to various demographic and geographic variables. At least one analysis showed that cities with higher levels of bicycle infrastructure (lanes and paths) also saw higher levels of bicycle commuting. This research affirms that finding by analyzing data from 35 large cities across the U.S. This cross-sectional analysis improves on previous research by including a larger sample of cities, not including predominantly ‘college towns,' and using consistent data from the Census 2000 Supplemental Survey. While the analysis has limitations, it does support the assertion that new bicycle lanes in large cities will be used by commuters.

An article from this research is published in the Transportation Research Record, No. 1828.

Vehicle Emissions and Oregon's Trip Permit Program

The State of Oregon, along with 35 other states and the District of Columbia, have vehicle inspection and maintenance (I&M) programs designed to help meet federal air quality standards. In Oregon, vehicles in the Portland and Rogue Valley areas are tested biennially and must pass the test in order to get a certificate required to register the vehicle with the Department of Motor Vehicles (DMV). One option to making costly repairs in Oregon is to obtain a “trip permit.” A trip permit allows vehicle owners that cannot otherwise register their vehicle (e.g. they failed to pass the emissions test) to register their vehicle for a limited time. One intent of the trip permit system is to provide a vehicle owner a legal way to drive their vehicle after failing an emissions test, but before making the repairs to pass the test. Starting January 1, 2002, the State implemented significant changes in the way trip permits for passenger cars, light trucks, and motorcycles are issued and tracked. The State now will issue no more than two 21-day permits in a 12-month period to any vehicle. In addition, the new system will track the permits via a computer database.

Previously, a vehicle owner could get a permit for up to 120 days in a 12-month period, and the permit records were not computerized. Therefore, under the old system, a vehicle owner whose vehicle failed the emissions test could operate legally with a trip permit for about four months. Because the permits were not tracked, owners could purchase successive permits at various DMV offices with little or no chance of being caught. Because the cost to repair a vehicle may often exceed the cost of the trip permits, this option may have attracted a significant number of vehicle owners. This was one motivation for changing the permit system and creating a computer system to track the permits.

This research project assessed the overall impacts of the new trip permit program on the operation of vehicles that fail emissions inspection. Key questions include:

Is there a change in the number of trip permits issued?
Has the new system resulted in vehicles getting fixed faster?
Are more vehicles being registered as a result of the new system?
If some vehicles are not fixed and registered after failing the inspection and getting the trip permit, are they being operated without a valid registration, registered outside the inspection area, scrapped, and/or moved/sold out of the inspection area?

One-page Project Summary (pdf)

Final Project Report (March 2005) (posted on TransNow web site)

This project was sponsored by the Transportation and Growth Management (TGM) Program. TGM is a joint effort of the Oregon Department of Transportation (ODOT) and the Oregon Department of Land Conservation and Development (DLCD). The program's mission is “to enhance Oregon's livability, foster integrated land use and transportation planning and development that results in compact, pedestrian-, bicycle-, and transit-friendly communities."

Link to materials and more information

Policymakers should consider ways to expand, improve, and/or supplement VAVR programs. First, adjustments to the methodology to calculate emissions reductions should be made to make the estimates more conservative. Second, policymakers should explore ways to change and supplement the programs to address key factors that reduce program effectiveness. Current programs are missing certain households that drive older vehicles a lot and have little impact on the vehicle replacement decision. Promising options include repair programs, targeting certain vehicles for participation in VAVR programs, and increasing the incentive for households that replace the vehicle with significantly cleaner alternatives.

Download Complete Dissertation (pdf, 3.5 MB)

Publications:

Dill, J. (2004) Scrapping Old Cars. Access. Spring 2004.

Dill, J. (2004) Estimating emissions reductions from accelerated vehicle retirement programs. Transportation Research Part D, 9(2): 87-106

Dill, J. (2001) The Design and Administration of Voluntary Accelerated Vehicle Retirement Programs in North America and Abroad. Transportation Research Record, 1750: 32-39.

This research was funded through an Eisenhower Graduate Fellowship and the University of California Transportation Center.

Back to Dill main page Courses I Teach My Research Resources for Students Information for Prospective Transportation Students Transportation Students and Alumni CV (pdf) CTS Weekly Transportation Seminar Photos	Research Projects and Areas of Interest Understanding and measuring bicycling behavior: Implications for urban planning, health, and research Estimating the Impacts of TODs on Travel and Transit Use Measuring Network Connectivity for Bicycling and Walking Travel Behavior and Land Use Bicycle Commuting in US Cities Land Use and Air Quality Environmental Streamlining Vehicle Emissions and Oregon's Trip Permit Program Transportation-Land Use: Outreach to Planning Commissioners Older Vehicles and Air Quality

	Understanding and measuring bicycling behavior: Implications for urban planning, health, and research With rates of obesity and related health problems increasing in the U.S., health professionals, urban planners, and policy makers are looking for ways to increase physical activity through changing urban form. Much of the focus is on walking. While walking is an attractive option for many reasons, bicycling offers many benefits and warrants further research. Over 60% of all personal trips are five miles or less in length – a reasonable distance to ride a bike – and nearly 40% are two miles or less. Given the potential for bicycling for both utilitarian travel and recreational purposes, why aren't more people cycling? This research is answering three questions: Examine the relationship between community environmental factors and people's decision to bicycle, including network connectivity, bicycle infrastructure, and land use; Examine other intervening factors influencing the decision to bicycle, such as weather, topography, attitudes and perceptions of subjective and objective factors, and socio-demographics; and Test the use of readily available technology to objectively measure physical activity of bicyclists. There were two major data collection efforts: (1) a survey of adults in the Portland, Oregon region; and (2) objective measures of bicycle use via a personal digital assistant (PDA) with a GPS monitor. This project is funded by the Active Living Research (formerly Active Living Policy and Environmental Studies) program of the Robert Wood Johnson Foundation. Some results from the phone survey of adults were presented in a paper at the TRB Annual Meeting in January 2007. This paper was subsequently revised and published: Dill, J., & Voros, K. (2007). Factors Affecting Bicycling Demand: Initial Survey Findings from the Portland, Oregon, Region. Transportation Research Record: Journal of the Transportation Research Board, 2031: 9-17. I presented some results from the GPS portion of the research at the Transportation Seminar on May 16 and at a Congressional briefing. The project had received some press attention on KGW and the Oregonian.
	Estimating the Impacts of TODs on Travel and Transit Use Many growing regions throughout the United States, including Portland, are turning to transit-oriented development (TOD) to address problems of traffic congestion and suburban sprawl. I've conducted several surveys of residents at Portland area TODs, with funding from PSU, Metro, and TransNow. Summary of results from survey of residents of The Merrick (April 2005) Full report of results from survey of residents of The Merrick. Travel and Transit Use at Portland Area Transit-Oriented Developments (TODs) (full final report from three station areas on the Westside and the Merrick, May 2006) Travel Choices at Transit-Oriented Developments: Survey Results from Portland’s Eastside (December 2007)
	Measuring Network Connectivity for Bicycling and Walking Advocates of New Urbanist and neo-traditional planning concepts include street connectivity as a key component for good neighborhood design. Street networks that are more grid-like are preferred over networks that include many cul-de-sacs and long blocks, thus increasing distances between destinations. The increased distances are thought to discourage walking and bicycling and, thus, physical activity. While intuitively attractive, there is limited empirical research at this time making this connection. There is also debate over how to measure connectivity and what levels of connectivity are appropriate. The current debate is particularly unclear because street connectivity is proposed to meet multiple, sometime conflicting objectives. In addition, most efforts to date have focused on the street network, which may differ from the pedestrian and bicycle network. The objective of this project is to develop measures of network connectivity that relate to bicycle and pedestrian behavior. We intend to develop measures that can be used by researchers developing empirical evidence linking (or not) connectivity to travel behavior, and planners who want to develop standards for new and existing development. We will develop the measures using GIS tools and data from the Portland, OR region and will evaluate the feasibility of applying the measures to other areas. This project is funded by the Active Living Research (formerly Active Living Policy and Environmental Studies) program of the Robert Wood Johnson Foundation. Project Summary Presentation at Pro-Walk Pro-Bike conference, September 2004 Paper presented at ACSP-AESOP 2003 (pdf, 1.2 MB) Time Frame: Final report expected soon
(photo by M. Laurer)	Travel Behavior and Land Use Neighborhood Scale: Many planners and designers claim that New Urbanist neighborhoods will encourage residents to walk and bicycle more and increase their sense of community. However, there is little empirical evidence to support these claims. Moreover, while some studies show that people living in New Urbanist-style neighborhoods walk more, it is unclear whether the neighborhood influenced the behavior or if people who want to walk chose to live in such a neighborhood. An example of a New Urbanist neighborhood is Fairview Village, just east of Portland, Oregon. In 2003 my students and I conducted a survey of residents of Fairview Village and two control neighborhoods. The surveys asked about travel behavior and attitudes. The findings reveal that residents in Fairview Village drove significantly fewer miles in private vehicles. Some of this difference is explained by lower vehicle ownership rates and smaller households. The adults in Fairview Village also made significantly fewer vehicle trips and more walking and bicycling trips during the week before the survey. The responses to the attitudinal questions on the survey indicate that many Fairview Village residents were looking for a place to live that enabled them to walk and bicycle more, they found it, and they are now walking and bicycling more. Paper presented at Transportation Research Board meeting in 2004 Dill, J. (2006). Evaluating a New Urbanist Neighborhood. Berkeley Planning Journal, 19, 59-78. Regional Scale: The Portland region has embarked on a number of efforts to reduce reliance on private vehicles. This conference presentation includes a number of performance measures (commute mode share for walking, cycling, and transit, transit trips per capita, VMT per capita, and congestion) and shows how Portland compares to regions of similar size (population).
	Bicycle Commuting in US Cities Some surveys indicate that providing bicycle lanes and paths may encourage more people to commute by bicycle. The presence of a striped lane or separated path can increase a cyclist's perception of safety. With growing concerns over traffic congestion and vehicle pollution, public policy makers are increasingly promoting bicycling as an alternative for commuting and other utilitarian trip purposes. States and local spending on bicycle facilities has increased significantly over the past decade. Previous studies have linked higher levels of bicycle commuting to various demographic and geographic variables. At least one analysis showed that cities with higher levels of bicycle infrastructure (lanes and paths) also saw higher levels of bicycle commuting. This research affirms that finding by analyzing data from 35 large cities across the U.S. This cross-sectional analysis improves on previous research by including a larger sample of cities, not including predominantly ‘college towns,' and using consistent data from the Census 2000 Supplemental Survey. While the analysis has limitations, it does support the assertion that new bicycle lanes in large cities will be used by commuters. An article from this research is published in the Transportation Research Record, No. 1828.
	Environmental Streamlining Many organizations feel that land use and environmental regulations and permitting procedures are time consuming and complicated to traverse and in many cases result in unacceptable delays in the design and construction schedule of a highway project. As a result, there is a nationwide push for “environmental streamlining” – a process to reduce the time needed for environmental review of highway projects. The Oregon Department of Transportation (ODOT) and its resource agency partners developed and are implementing a coordinated environmental review process for the development, design and construction of highway projects. The Collaborative Environmental and Transportation Agreement on Streamlining (CETAS) was developed to conform to Section 1309 of the Transportation Equity Act for the 21 st Century (TEA-21) which required the Federal Highway Administration to pursue streamlining of environmental compliance procedures. My colleague, Connie Ozawa, and I conducted an early evaluation of CETAS. The project intended to answer two sets of questions. First, are the highway projects completed more efficiently? More specifically, are the land use and environmental reviews conducted in a more timely manner and are projects costs reduced? Second, are the environmental results of highway projects improved in frequency and/or magnitude? To answer these questions, we collected extensive data on highway projects completed before CETAS was initiated. The research is uncovering multiple explanations for highway project delays, including and other than the land use and environmental review. The intent is to eventually collect similar information on projects that went through the CETAS process. In the meantime, we conducted interviews of key participants in CETAS to assess their perceptions of the process. This project is complete. The final report is here.
	Vehicle Emissions and Oregon's Trip Permit Program The State of Oregon, along with 35 other states and the District of Columbia, have vehicle inspection and maintenance (I&M) programs designed to help meet federal air quality standards. In Oregon, vehicles in the Portland and Rogue Valley areas are tested biennially and must pass the test in order to get a certificate required to register the vehicle with the Department of Motor Vehicles (DMV). One option to making costly repairs in Oregon is to obtain a “trip permit.” A trip permit allows vehicle owners that cannot otherwise register their vehicle (e.g. they failed to pass the emissions test) to register their vehicle for a limited time. One intent of the trip permit system is to provide a vehicle owner a legal way to drive their vehicle after failing an emissions test, but before making the repairs to pass the test. Starting January 1, 2002, the State implemented significant changes in the way trip permits for passenger cars, light trucks, and motorcycles are issued and tracked. The State now will issue no more than two 21-day permits in a 12-month period to any vehicle. In addition, the new system will track the permits via a computer database. Previously, a vehicle owner could get a permit for up to 120 days in a 12-month period, and the permit records were not computerized. Therefore, under the old system, a vehicle owner whose vehicle failed the emissions test could operate legally with a trip permit for about four months. Because the permits were not tracked, owners could purchase successive permits at various DMV offices with little or no chance of being caught. Because the cost to repair a vehicle may often exceed the cost of the trip permits, this option may have attracted a significant number of vehicle owners. This was one motivation for changing the permit system and creating a computer system to track the permits. This research project assessed the overall impacts of the new trip permit program on the operation of vehicles that fail emissions inspection. Key questions include: Is there a change in the number of trip permits issued? Has the new system resulted in vehicles getting fixed faster? Are more vehicles being registered as a result of the new system? If some vehicles are not fixed and registered after failing the inspection and getting the trip permit, are they being operated without a valid registration, registered outside the inspection area, scrapped, and/or moved/sold out of the inspection area? One-page Project Summary (pdf) Final Project Report (March 2005) (posted on TransNow web site)
	Transportation-Land Use: Outreach to Planning Commissioners This project was undertaken by a team of graduate students and faculty at the School of Urban Studies and Planning at Portland State University. The project involved outreach activities to planning commissioners in the State of Oregon regarding policies and programs to integrate land use and transportation planning. Students developed written materials and a powerpoint presentation for use at outreach workshops with local planning commissioners. The project involved teams at both Portland State University (PSU) and University of Oregon (UO). Each team worked independently, but coordinated their efforts. The project spanned winter and spring quarters, January through June 2003. This project was sponsored by the Transportation and Growth Management (TGM) Program. TGM is a joint effort of the Oregon Department of Transportation (ODOT) and the Oregon Department of Land Conservation and Development (DLCD). The program's mission is “to enhance Oregon's livability, foster integrated land use and transportation planning and development that results in compact, pedestrian-, bicycle-, and transit-friendly communities." Link to materials and more information
	Older Vehicles and Air Quality My dissertation research focused on this topic: Older vehicles contribute a significant and disproportionate share of the pollution in urban areas. Starting in 1990, several areas adopted voluntary accelerated vehicle retirement (VAVR) programs to address this problem and to respond to demands for flexible, market-based approaches to controlling air pollution. VAVR programs offer owners of older vehicles cash to scrap their vehicles. VAVR programs have been adopted throughout the U.S. and abroad, though not without controversy and uncertainty over the programs' benefits. This research first examined the roles of older vehicles in U.S. households. Lower income households are more likely to own older vehicles and to rely upon them more for their daily transportation needs. While older vehicles are generally driven less than newer vehicles, they serve a wide range of roles within households. This makes estimating the emissions reduction benefits of VAVR programs more difficult. This research then examined how household characteristics and behavior influence participation in VAVR programs and, therefore, the benefits from the programs. The assumptions used by regulators to estimate the air pollutant reductions from VAVR programs are compared with data from VAVR programs in California. Changing the assumptions did significantly change the estimated benefits. However, in nearly all the scenarios examined, the programs still reduce emissions significantly, particularly of reactive organic gases. Data from surveys of program participants show that the programs are diverting vehicles from the used vehicle market, which is not built into the current assumptions for estimating program benefits. The scrapped vehicles are generally in poorer condition, are worth less, and are driven less than other older vehicles. However, the criticism that most of the scrapped vehicles were headed to the junkyard anyway appears unfounded. Nearly all of the scrapped vehicles were replaced with another vehicle and nearly all of the replacement vehicles were newer than the scrapped vehicles. Policymakers should consider ways to expand, improve, and/or supplement VAVR programs. First, adjustments to the methodology to calculate emissions reductions should be made to make the estimates more conservative. Second, policymakers should explore ways to change and supplement the programs to address key factors that reduce program effectiveness. Current programs are missing certain households that drive older vehicles a lot and have little impact on the vehicle replacement decision. Promising options include repair programs, targeting certain vehicles for participation in VAVR programs, and increasing the incentive for households that replace the vehicle with significantly cleaner alternatives. Download Complete Dissertation (pdf, 3.5 MB) Publications: Dill, J. (2004) Scrapping Old Cars. Access. Spring 2004. Dill, J. (2004) Estimating emissions reductions from accelerated vehicle retirement programs. Transportation Research Part D, 9(2): 87-106 Dill, J. (2001) The Design and Administration of Voluntary Accelerated Vehicle Retirement Programs in North America and Abroad. Transportation Research Record, 1750: 32-39. This research was funded through an Eisenhower Graduate Fellowship and the University of California Transportation Center.
Page updated July 21, 2008