Research Projects and Resources
The STC research program supports projects that address the concerns of transportation agencies while meeting the most rigorous academic standards. Research funded through STC fellowships and grants directly supports national transportation research priorities as articulated in the National Highway R&T Partnership’s Highway Research and Technology: The Need for Greater Investment and the U.S. Department of Transportation Strategic Plan 2003-2008, particularly in the areas of environment, mobility, planning, and infrastructure. Each project is selected based on the reviews of researchers from outside of UC Davis.
STC funds five faculty research grants each year. Each project supports at least one graduate student and integrates education into the research process.
Current-Year Faculty Research Grants
R04-1 |
Alison M. Berry One key ecological problem to solve in roadside management is how to reduce detrimental effects of increased runoff from paved surfaces (“hydromodification”), that increase sediment movement, destroy aquatic habitat, and redistribute road-source pollutants. The Advanced Transportation Infrastructure Research Center (ATIRC) is a newly-built facility at UC Davis that offers unique opportunities for collaborative and integrative research that can potentially improve sustainable management of the state’s vegetated road-edge environment. This proposal builds on a 2003 California Department of Transportation (Caltrans) study, Roadside Vegetated Treatment Sites (RVTS) that estimated infiltration and contaminant adsorption into road-edge soil as a function of slope length for five California road edge locations, but measured only the top 2 inches of soil. |
R04-2 |
Yueyue Fan We propose to develop methods for sequentially building infrastructure systems, with an objective of achieving system efficiency, security, and sustainability. A mathematical model that integrates multistage optimization techniques and various risk measures will be developed to identify the optimal sequence of expanding or repairing a given network. Various sustainability measures will be considered including economic cost effectiveness, system security and robustness, and environmental and resource impact. The incorporation of system uncertainties and risks into the network design model via stochastic modeling techniques provides improves the reliability and safety of the system, which is an important sustainability measure. The multistage framework allows optimal usage of resources and provides more flexibility for adjusting future planning activities based on acquired information through information technologies. Case studies of transportation network expansion and repairing using San Francisco Bay Area data will be carried out for numerical testing, sensitivity analysis of model parameters, and policy implications. |
R04-3 |
Susan Handy As a means of transportation and as a form of physical activity, bicycling generates benefits to the bicyclist as well as to the community as a whole. Bicycling now accounts for less than 1 percent of all trips for all purposes in the U.S., but evidence from other western countries suggests that under the right conditions, bicycling levels can be significantly higher. The experience of Davis, California suggests that it is possible to create conditions conducive to higher levels of bicycling in the U.S. However, analysis of data collected using an on-line survey in Davis and five comparison cities in early fall 2006 shows that cognitive factors, particularly preference for bicycling and comfort level with bicycling, play a critical role in explaining bicycling behavior. |
R04-4 |
Susan Ustin Wildlife-vehicle collisions are economic, safety, and ecological costs of transportation systems. Although understanding of the reasons that collisions occur is increasing, for most road and highway systems in California and elsewhere, the proximate causes and contributing environmental and other factors are unknown. Most contemporary research points to the importance of existing road and highway systems in reducing habitat quality and imperiling species. Currently, highway and other transportation projects are generally planned, funded and designed before considering the potential impacts to wildlife and sensitive biological resources. By identifying critical wildlife movement needs in relation to transportation systems, transportation and other planners will have improved abilities to predict and mitigate (avoid, minimize, or compensate for) wildlife impacts. We propose to study the occurrence and movement of small and medium-sized mammals across development and traffic gradients adjacent to I-80 as it bisects the Sierra Nevada. |
R04-5 |
Michael Zhang The theory of first-best congestion pricing tells us that a time-dependent toll can be used to eliminate congestion in the morning commute problem for identical commuters in a corridor with a single bottleneck. In reality, however, it is often impractical to implement such a fine-gained toll because it would require too frequent changes of the toll. In this research, we investigate a coarse-grained, second best tolling scheme in which a flat toll is collected during a particular time period in the morning peak. In this scheme, both the toll and its duration are subject to optimization. We will first find the commuter departure profiles under this coarse tolling scheme for identical commuters, then for heterogeneous commuters who have different values of time. |
R04-5 |
Michael Zhang The theory of first-best congestion pricing tells us that a time-dependent toll can be used to eliminate congestion in the morning commute problem for identical commuters in a corridor with a single bottleneck. In reality, however, it is often impractical to implement such a fine-gained toll because it would require too frequent changes of the toll. In this research, we investigate a coarse-grained, second best tolling scheme in which a flat toll is collected during a particular time period in the morning peak. In this scheme, both the toll and its duration are subject to optimization. We will first find the commuter departure profiles under this coarse tolling scheme for identical commuters, then for heterogeneous commuters who have different values of time. |
R04-6 |
Patricia Mokhtarian For the nine weeks of June and July, 2008, a one-mile stretch of Interstate 5 (I-5) in downtown Sacramento was intermittently closed for reconstruction. Among other evaluation efforts, we conducted an internet survey of commuters potentially affected by the closure, with three key goals in mind: (1) to understand the extent and nature of the impacts on commuters; (2) to assess what commuters did in response; and (3) to monitor the persistence of any changes made during the Fix, after freeway operations returned to normal. The initial project budget permitted only descriptive tabulations and crosstabulations of the data, which are still underway. Here, we propose to extend the analysis to begin modeling the adoption of commute changes, and the intention to maintain those changes after the Fix was completed. Such models will provide a clearer picture of how multiple factors act together to increase or decrease the propensity to change. The results could help predict the impacts of future network disruptions of this nature, and will add to our understanding of the effects of programs promoting voluntary behavior change. |
Year-Three Faculty Research Grants
R03-1 | Susan Handy As a means of transportation and as a form of physical activity, bicycling generates benefits to the bicyclist as well as to the community as a whole. Bicycling now accounts for less than 1 percent of all trips for all purposes in the U.S., but evidence from other western countries suggests that under the right conditions, bicycling levels can be significantly higher. The experience of Davis, California suggests that it is possible to create conditions conducive to higher levels of bicycling in the U.S. However, the extent to which bicycling policy has contributed to bicycling levels in Davis has not been rigorously assessed. This project aims to fill that gap through a series of studies of bicycling behavior in Davis and comparison communities designed to determine the influence of bicycle infrastructure and mixed-use land use patterns relative to individual preferences, community culture, and other factors. This project focuses on the analysis of data collected using an on-line survey in Davis and five comparison cities in early fall 2006, supplemented by a follow-up phone survey of Davis residents completed in spring 2008 and complemented by interviews to be conducted with Davis residents as a part of the proposed project. This project continues Phases 2 and 3 of the Davis Bicycle Studies. |
R03-2 | Pat Mokhtarian From early studies of time allocation onward, it has been acknowledged that the “productive” nature of an activity such as travel could affect its utility. Yet until recently, there has been very little empirical assessment of such an effect, in particular the potential effect of activities con¬ducted while traveling on the (dis)utility of the trip and thence the value of travel time savings for such a trip. The proposed investigation aims to make a contribution to the small but growing literature on travel multi-tasking. Specifically, in this continuation of a multi-year study, we plan to proceed with a conceptualization of travel multi-tasking, including the development of a typo¬logy based on dimensions such as motivation, effect, equippedness, passivity/activity, and others. In addition, we will design a survey intended to measure travel multi-tasking attitudes and behaviors, sociodemographic traits and other relevant variables, together with a stated preference exercise in which respondents will be asked to choose between travel alternatives varying on the dimensions of time, cost, and ability to multi-task. We will also develop the sampling and ad¬ministration plan for the survey, preparatory to conducting it the following year should con¬tinu¬ation funding be approved. |
R03-3 | Michael Zhang Urban traffic congestion, with all its negative effects on travel safety, productivity, fuel efficiency and the environment, is becoming an increasingly important issue to address for modern societies. Congestion occurs when travel demand exceeds the carrying capacities of the roadways, but it is not economical to provide capacity that meets the highest demand (thus eliminate congestion all together), because of peaking in urban travel. Economists have suggested the use of congestion pricing to combat traffic congestion. By internalizing the \ congestion externality into travelers' commute costs, a time-dependent toll was shown to able to rid the roadway of congestion entirely. In practice, however, congestion pricing has encountered sizable resistance from the public because it's often perceived as another tax. |
R03-4 | Deborah Salon Transit advocates argue that good transit systems promote urban economic development by improving job matching between employers and workers who do not commute by car. As urban economies enter an era of high fuel prices, high traffic congestion, and increasing concern about our global climate, increasing numbers of commuters will be looking to alternatives to the private car, including transit. We aim to test the strength of the relationship between transit expansion and employment outcomes using the case of Bogotá, Colombia – a city that recently made an enormous investment in transit with economic development as an explicit goal. We focus on Bogotá because it presents a rare “natural experiment” in transit investment. We plan to employ a variety of empirical strategies using existing geocoded data from a labor market survey conducted each quarter from 2000-2005, along with information about the exact timing and location of the transit expansion over this same time period. The proposed research will provide the first empirical test of whether a real-world major investment in urban transit infrastructure actually improved employment outcomes across a city, and if so, for whom. |
R03-5 | Dave Rapson The primary goal of this project is to inform policymakers regarding the optimal policies to promote biofuels. Ethanol production in the U.S. has increased rapidly in recent years, propelled by high gasoline prices and government subsidies that, combined, induce entry into the industry. Complex interactions ("indirect network effects") exist between subsidies that influence agricultural land use decisions and those that affect the entry and location of ethanol refineries. In this project, we will build an empirical model that will estimate the impact of food, ethanol, and capital prices on entry into the ethanol refinery industry, and the effect that new refineries have on agricultural land use. Results will also inform the current "food versus fuel" debate, both by quantifying the extent of its validity and exploring potentially efficient re-allocations of resources. |
Year-Two Faculty Research Grants
R02-1 |
Alison Berry Roads and road networks have environmental impacts that vary in type and degree based on the physical properties of the roadway, the activities associated with the road, and the sensitivity of the local environment. The local environment affected by the road surface and traffic has been termed the “road effect zone”. Although there is a rapidly growing literature on specific environmental impacts within this zone (storm-water runoff effects, biological invasions, noise, wildlife barriers), there have been few tests of the extent of the road effect zone, how various impacts are interrelated, and how these impacts could be minimized through pavement and roadside management activities. The objectives of the proposal are: 1) To develop a long-term integrated experimental site at the newly-established UC Davis Advanced Transportation Infrastructure Research Center, and 2) To establish a modeling framework for future research on the road effect zone, with special emphasis on defining parameters of relevance for California road systems, but with methodologically broader applicability. |
R02-2 |
Mark Delucchi We propose that it is possible to build communities that accommodate strong preferences for auto-mobility and single-family homes, yet at the same time are much safer and cleaner, more pleasant, and more socially integrated than conventional suburbs. We accomplish this with a dual transportation infrastructure: the complete separation of fast, heavy vehicles (FHVs) from low-speed, low-speed, lightweight modes (LLMs; less than 25 mph top speed and 500 kg curb weight) on a city-wide scale. In a draft report (Delucchi et al, 2002) we delineate our dual-road-system plan and discuss and analyze some of its impacts on transportation problems. The potential environmental, social, and community benefits of the plan are clear. However, for these benefits to be realized, people must choose to live in such planned communities and to buy and use LLMs. Because there are no communities like the one we propose, one must use simulations to begin to understand how people might react to our plan. We seek STC funding to design and administer “pilot” household interviews, focus groups, and other group interviews to investigate: i) effective ways to represent or simulate life and travel in our plan; ii) how people react to various aspects of the plan; iii) the implications of our initial findings for developing the plan to maximize its appeal to households, and iv) the practical problem of how to start to build such towns as we propose. |
R02-3 |
Yueyue Fan We propose to develop methods for sequentially building networks of HOT lanes, with objective of achieving system efficiency, social equitability, and financial sustainability. A mathematical model that integrates multistage decision processes, optimization techniques, and user behavior model will be developed to identify the optimal sequence of converting existing and under-construction HOV facilities to HOT lanes and the associated pricing strategies. Various system performance measures will be considered including total toll revenue, total vehicle delay, and total costs for the users. The requirement on equitability, measured by the gap between the rich and the poor in terms of benefits from the implementation of HOT lanes, is explicitly included as model constraints to ensure a solution that is more likely to be accepted by all income groups. The multistage framework allows optimal usage of toll revenue gained from implemented HOT segments for financing future HOT projects, thus imposes less financial burden on public agencies and future generations. These unique modeling treatments are proposed to enhance the overall sustainability of the transportation network in question. Case studies based on selected corridors in San Francisco Bay Area will be carried out for numerical testing, sensitivity analysis of model parameters, and policy implications. |
R02-4 |
Susan Handy As a means of transportation and as a form of physical activity, bicycling generates benefits to the bicyclist as well as to the community as a whole. Bicycling now accounts for less than 1 percent of all trips for all purposes in the U.S., but evidence from other western countries suggests that under the right conditions, bicycling levels can be significantly higher. The experience of Davis, California suggests that it is possible to create conditions conducive to higher levels of bicycling in the U.S. However, the extent to which bicycling policy has contributed to bicycling levels in Davis has not been rigorously assessed. This project aims to fill that gap through cross-sectional and quasi-longitudinal studies of bicycling behavior in Davis and comparison communities designed to determine the influence of bicycle infrastructure and mixed-use land use patterns relative to individual preferences, community culture, and other factors. This project focuses on the analysis of data collected using an on-line survey in Davis and five comparison cities in early fall 2006 and the development of a survey of students at Davis High and selected comparison schools. This project completes Phase 1 and begins Phase 2 of the Davis Bicycle Studies. |
R02-5 |
Patricia Mokhtarian Fully understanding the potential transportation impacts of new (internet) and old (going to the store, catalog) shopping alternatives requires investigating the adoption of the various alternatives. By now, numerous studies have analyzed (intended or actual) purchase or pre-purchase (search) behavior, but we are not aware of any empirical studies considering the combined choices of pre-purchase and purchase modes. Yet it is important to understand those choices not as separate and independent, but rather as interrelated. This study continues the substantive analysis of data collected from an original survey of shopping attitudes and behavior, in this phase investigating the combined choices of pre-purchase and purchase modes (primarily store and internet, but also catalog and other pre-purchase modes). We propose to (1) cluster cases based on a variety of possible pre-purchase/purchase mode patterns; (2) conduct descriptive analyses of the resulting clusters, using the large variety of personality, attitudinal, situational, and sociodemographic variables available to us; and (3) develop multivariate probit and/or multidimensional nested logit models of pre-purchase and purchase mode choice combinations. The findings will have important implications for transportation planning as well as for the retail industry. |
Year-One Faculty Research Grants
R01-1 |
Alison Berry Transportation planners increasingly need effective metrics for determining the effect of transportation systems on biological systems. Developing the metric and measuring the impact is the first step toward mitigation. Professor Alison Berry proposes to develop effective mesh size, effective mesh density and landscape division as metrics of habitat fragmentation for use in transportation planning. These innovative and biologically meaningful measures of landscape fragmentation will be applied to the mapped ranges of 10 key animal species. Final products from the proposed effort will serve as a model and metric for transportation planners throughout the world. |
R01-2 |
Susan Handy Bicycling now accounts for less than 1 percent of all trips for all purposes in the United States, but evidence from other western countries suggests that under the right conditions, bicycling levels can be significantly higher. The experience of Davis, California suggests that it is possible to create conditions conducive to higher levels of bicycling in the U.S. However, the extent to which bicycling policy has contributed to bicycling levels in Davis has not been rigorously assessed. This project aims to fill that gap through a quasi-experimental study of bicycling behavior in Davis and comparison communities. The study will be designed to determine the influence of bicycle infrastructure and mixed-use land use patterns relative to individual preferences, community culture, and other factors. |
R01-3 |
Ken Kurani Rising gasoline prices, greenhouse gas emissions, and war in oil-producing regions motivate this research on whether drivers would reduce their petroleum consumption if they received feedback on their energy use. This proposed study examines effects of energy-use feedback on household drivers of conventional and hybrid light-duty passenger vehicles. Drivers will be interviewed and commercially available devices will be installed in some drivers’ vehicles. This qualitative study is expected to produce insights into specific types of driver response to feedback mechanisms and to produce the requisite knowledge to design and deploy a larger scale study to produce estimates of effects that can be generalized. |
R01-4 |
Michael Zhang We hypothesize that using a realistic dynamic flow model may significantly alter the policy implications and welfare effects of a time-varying toll derived from the basic bottleneck model. In the proposed research, we plan to test our hypothesis by exploring dynamic congestion pricing on a wide variety of simple yet general networks with a more realistic traffic flow model. To achieve this objective, we will formulate, solve and analyze the dynamic congestion pricing problem via traffic equilibrium analysis and network optimization, and discuss the policy implications of our research findings. |
R01-5 |
Patricia Mokhtarian Why do some individuals want to travel more, and others less? Just asking this question is novel, as most transportation researchers consider travel to be strictly a cost necessary to participate in daily life activities. That premise is challenged here in a “first principles” examination of travel behavior. Four key travel-related constructs are defined: objective mobility, subjective mobility, travel liking, and relative desired mobility. A 1998 survey measured these variables for travel segmented by length, purpose, and mode, as well as attitudes, personality, lifestyle, and socio-demographics, for more than 1,300 workers in the San Francisco Bay Area. Prior analysis of this dataset has involved only single-equation models, and has exposed considerable endogeneity among the four key constructs. Here, structural equation modeling will be used to sort out the inter-relationships among these endogenous variables, as well as other relationships present in the dataset. The findings will have important implications for our understanding and prediction of travel behavior. |