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Open Access Publications from the University of California

The University of California Transportation Center recognizes that transportation is one component of a societal system that is affected by and has effects on the movement of goods, people, and information. The Center draws on the knowledge of many disciplines, including but not limited to engineering, economics, urban planning, and management in its efforts to support studies that analyze transportation systems and the public policies that are integral to them.

The Center is sponsored by both the United States Department of Transportation (DOT) and the California Department of Transportation (Caltrans). All transportation-related programs within the University of California campuses are eligible for research and educational funding from the Center. The primary campuses involved in UCTC activities are those at Los Angeles, Davis, Irvine, and Berkeley.

UCTC maintains an active program of basic and applied research conducted by University of California faculty and graduate student assistants. The Center supports the University's educational programs in transportation with awards of scholarships and fellowships to students planning careers in transportation. As part of its technology-transfer activities, UCTC sponsors seminars and conferences where scholars and public officials meet to exchange information and research findings. The Center also publishes the results of research it has funded in the form of working papers, reprints of journal articles, and in its official magazine, ACCESS. These publications are distributed widely within the academic, professional, and governmental communities.

Cover page of Quantified Traveler: Travel Feedback Meets the Cloud to Change Behavior

Quantified Traveler: Travel Feedback Meets the Cloud to Change Behavior


We describe the design and evaluation of a system named Quantified Traveler (QT). QT is a Computational Travel Feedback System. Travel Feedback is an established programmatic method whereby travelers record travel in diaries, and meet with a counselor who guides her to alternate mode or trip decisions that are more sustainable or otherwise beneficial to society, while still meeting the subject’s mobility needs. QT is a computation surrogate for the counselor. Since counselor costs can limit the size of travel feedback programs, a system such as QT at the low costs of cloud computing, could dramatically increase scale, and thereby sustainable travel. QT uses an app on the phone to collect travel data, a server in the cloud to process it into travel diaries and then a personalized carbon, exercise, time, and cost footprint. The subject is able to see all of this information on the web. We evaluate with 135 subjects to learn if subjects let us use their personal phones and data-plans to build travel diaries, whether they actually use the website to look at their travel information, whether the design creates pro-environmental shifts in psychological variables measured by entry and exit surveys, and finally whether the revealed travel behavior records reduced driving. Before and after statistical analysis and the results from a structural equation model suggest that the results are a qualified success.

Cover page of Getting the Prices Right: An Evaluation of Pricing Parking by Demand in San Francisco

Getting the Prices Right: An Evaluation of Pricing Parking by Demand in San Francisco


Underpriced and overcrowded curb parking creates problems for everyone except a few lucky drivers who find a cheap space; all the other drivers who cruise to find an open space waste time and fuel, congest traffic, and pollute the air. Overpriced and underoccupied parking also creates problems; when curb spaces remain empty, nearby merchants lose potential customers, workers lose jobs, and cities lose tax revenue. To address these problems, San Francisco has established SFpark, a program that adjusts parking prices to achieve a target parking availability of one or two open spaces on each block. To measure how parking prices affected parking occupancy in San Francisco we calculated the price elasticity of demand for on-street parking revealed by 5,294 individual price and occupancy changes during the program’s first year. Price elasticity varies greatly by time of day, location, and several other factors, with an average value of –0.4. The average meter price fell 1 percent during the first year, so SFpark adjusted prices up and down according to local demand without increasing prices overall. The city can improve the program by making drivers more aware of the variable prices, reducing the abuse of disabled parking placards, and introducing seasonal adjustments for parking prices. 

Cover page of Bike-and-Ride: Build It and They Will Come

Bike-and-Ride: Build It and They Will Come


Converting park-and-ride to bike-and-ride trips could yield important environmental, energy conservation, and public-health benefits.  While cycling in general is becoming increasingly popular in the United States, it still makes up a miniscule portion of access trips to most rail transit stations.  At several rail stations of the Bay Area Rapid Transit (BART) system, 10 percent or more of access trips are by bicycle, up considerably from a decade earlier.   This paper adopts a case-study approach to probe factors that have had a hand in not only cycling grabbing a larger market share of access trips to rail stops but also in the enlargement of bike access-sheds over time.   Both on-site factors, like increases the number of secure and protected bicycle parking racks, as well as off-site factors, like increases in the lineal miles of bike-paths and bike boulevards, appear to explain growing use of bicycles for accessing rail stations. The adage “build it and they will come”, we argue, holds for bicycle improvements every bit as much as other forms of urban transportation infrastructure.  Pro-active partnerships between transit agencies, local municipalities, and bicycle advocacy organizations are critical to ensuring such improvements are made. 

Cover page of What's Youth Got to Do with It? Exploring the Travel Behavior of Teens and Young Adults

What's Youth Got to Do with It? Exploring the Travel Behavior of Teens and Young Adults


Today’s teens are members of the first generation to have never known a world without instantaneous and nearly ubiquitous mobile phone access. They also must surmount greater hurdles to driver’s licensing than any previous generation faced. And they are struggling to transition into the most unwelcoming job market since the Great Depression. These tectonic happenings surely augur equally dramatic changes in the travel choices and patterns of young adults in the years ahead. Or will they? This report examines this question. 

While scholars have studied the travel choices and patterns of adults extensively over the years, our knowledge of youth travel behavior is surprisingly limited and uneven. There is a growing body of research on how children travel to school and a second body of research on youth and travel safety, in particular, the high rates of crashes and driving fatalities among teenagers. Beyond these two rather focused lines of inquiry, however, studies of travel by children, teens, and young adults are rare. 

Researchers have posited several factors to explain differences in the travel behavior of youth and adults, and to support the argument that such differences may persist as today’s youth move into adulthood. First, the rapid profusion and adoption of new communication technologies influences how people use their time and may affect how much they travel (Kwan, 2002), and young people tend to be early and frequent adopters of these technologies (Mans et al., forthcoming; Lenhart et al., 2005; Pew Research Center, 2010b). Second, all 50 states have now adopted graduated driver’s licensing programs, making teen licensing more difficult and restrictive (with respect to time, trip purpose, and passengers) than in previous eras (Insurance Institute for Highway Safety, 2012). Third, unemployment rates during the current recession are highest for youth, thereby reducing journey-to-work and work-related travel and limiting the resources teens and young adults have to pay for non-work activities (and associated travel) of all types. This prolonged economic downturn may also influence youth travel patterns indirectly; fragmentary evidence suggests that young adults struggling to find work increasingly “boomerang” back home to live with parents (Kaplan, 2009; Pew Research Center, 2010b; Wiemers, 2011), drawn by a free or steeply discounted bedroom, groceries, and, perhaps, access to parents’ cars.

Cover page of Safe Routes to Play? Pedestrian and Bicyclist Crashes Near Parks in the Los Angeles Region

Safe Routes to Play? Pedestrian and Bicyclist Crashes Near Parks in the Los Angeles Region


Rationale: Areas near parks may present active travelers with higher risks than in other areas due to the confluence of more pedestrians and bicyclists, younger travelers, and the potential for increased numbers of motor vehicles. These risks may be amplified in low-income and minority neighborhoods due to generally higher rates of walking or lack of safety infrastructure. 

Objectives: We pursued three research objectives: (1) to determine if pedestrian and bicycle crashes occur at higher rates in park-adjacent neighborhoods compared to the rest of the study area; (2) to identify if demographic characteristics predict active crash risk after controlling for population and the rate of active trips; and (3) to assess if there is an amplified effect of park proximity for active crash risk in low-income and minority neighborhoods after controlling for population and the rate of active trips. 

Methods: With negative binomial regression modeling techniques, we used ten years of geolocated pedestrian and bicyclist crash data and a quarter mile (~400 meter) buffer around public parks to assess the risk of active travel near parks. We controlled for differential exposures to active travel risks using travel survey data. 

Measurements: Quarter-mile network buffers were designated around parks from the Green Visions Plan for 21st Century California in 2249 census tracts. Crashes came from the 90,846 pedestrian and bicyclist injuries and fatalities from the Statewide Integrated Traffic Reporting System, and active travel was predicted using travel data from 9135 households that participated in the Southern California Association of Governments 2001 Travel and Congestion Survey. These data were combined with demographic and income data from the U.S. Census and traffic density predictions. 

Results: The ratio of active crashes per 100,000 population within the quarter-mile park buffer to those outside is 1.52. The increased risk of crash for active travelers near parks remained after adjusting for varying rates of active travel in different census tracts. Minority and low-income residents of the study area are more likely to walk or bicycle than White and higher-income residents. This higher risk near parks is amplified in neighborhoods with high proportions of minority and low-income people. Higher traffic levels are highly predictive of active crashes.

Conclusions: Active travelers accessing parks may lack a safe route to places for play. The socioeconomic modification of active crashes near parks found in this study is supported by existing research showing disparities in park access and higher active travel risks in low-income and minority neighborhoods.

Cover page of Does Transit Mean Business? Reconciling academic, organizational, and political perspectives on Reforming Transit Fare Policies

Does Transit Mean Business? Reconciling academic, organizational, and political perspectives on Reforming Transit Fare Policies


Public transit systems differ from many other government enterprises in that they charge a fee, or fare, in much the way that private businesses charge for their services. Transit fares are typically of two sorts: flat or differentiated. For decades transportation scholars have argued in favor of flexible, differentiated transit fares, which vary by mode, distance, and/or time-of-day to reflect differences in the marginal costs of service provision (Cervero and Wachs 1982; Cervero 1981; Hodge 1995). Such fare policies, researchers contend, could greatly increase the efficiency, efficacy, and equity of transit service. Research on transit costs suggests that short, off-peak trips tend to be relatively inexpensive to provide, while longer, peak-period trips are more expensive (Taylor, Garrett, and Iseki 2000). Accordingly, varying fares to reflect these differences in costs would encourage passengers to consume more inexpensive-to-serve trips, and be more judicious in consuming more expensive-to-serve trips, thereby increasing the cost-effectiveness of transit service. 

Recent technological advances, particularly smart cards, have greatly reduced the operational and administrative obstacles to charging differentiated time- or distance-based fares. However, despite an established body of research on the potential benefits of flexible fares, relatively few transit agencies employ them, and over the past two decades many have actually moved away from variable fare structures and toward simpler fares by dropping zonebased fares. And while many U.S. transit agencies that have adopted smart card technology, very few of these adopting agencies have moved toward variable fares. 

The increasingly widespread implementation of smart farecards makes implementing variable pricing far easier and more reliable than in years past. As smart cards become more ubiquitous, will transit systems gradually reverse course and begin implementing differentiated fares? Will political and institutional resistance to variable pricing hold firm, suggesting that implementation was never the principal obstacle? Or have flat fares become so thoroughly inculcated in transit practice that most transit managers are unaware of the now decades old research on the benefits of differentiated fares? This report explores these questions. 

To better understand motivations for fare changes and the potential for implementing marginal cost pricing, we reviewed the literature on transit fares and pricing, conducted indepth interviews with California transit officials, and administered a nationwide survey of transit agency CEOs, planners and analysts, and board members on the goals that shape fare policies.

Collectively, these interviews and survey find that, with respect to fare policies, transit agencies tend to be reactive to budgetary pressures and reluctant to change fare structures when changing fare levels. Despite this observed lack of strategic thinking with respect to fares, we do see in our survey data some, albeit limited, interest in distance- and time-based fares, especially among agencies that have or soon will introduce smart cards. But any opportunities to move toward differentiated fares created by smartcard adoption are constrained by an industry where simple, flat fares are the norm and were transit managers are risk-averse and seek to minimize public scrutiny and criticism. Smart cards, in other words, are a necessary but not sufficient means of fare innovation in public transit. Beyond this general observation, our interview and survey results collectively suggest three specific findings with respect to transit fare setting: 

1. With respect to fare policies, transit agencies tend to be reactive to budgetary pressures and reluctant to change fare structures when changing fare levels. 

Our survey results find that systematic evaluations of fare policies are subject to and often displaced by the immediate needs of an agency’s budget. Respondents indicated that the primary consideration for changing fares is budgetary need, implying a focus on near-term responses to fiscal shortfalls in setting fare policies. Changing fare policies to improve farebox recovery ratios, possibly through marginal cost pricing, which research suggests may improve a given agency’s fiscal health over the long term received considerably less consideration. Rational (i.e., cost- or criteria-based) fare setting policies are viewed as important, but in practice the setting of transit fares appears to be almost exclusively budget-driven and fare increases are more often than not induced by fiscal crises. Because transit systems depend so heavily on subsidies, large swings in tax revenues – especially during the current, prolonged economic downturn – can make transit budgets volatile. When rising costs and/or cuts in subsidies threaten service, fare increases are often put on the table in conjunction with service cuts – at what some would argue is precisely the wrong time. While economists have long asserted the superiority of cost-based pricing on economic efficiency grounds, agency policy setting driven by near-term budgetary volatility almost certainly limits reflection on and adoption of such strategies. 

This finding also suggests that the crisis-induced and budget-driven fare setting processes may not themselves be the problem, but rather are a manifestation of unclear or contradictory goals. Clearly defined and congruent agency goals and objectives allow staff to work toward given objectives, and board members to defend their decisions in light of these v objectives. But given the often competing and contradictory goals for public transit (reduce congestion and emissions, serve the needs of the poor and disabled, keep subsidies low, provide quality employment for workers, keep fares low, etc.), goal-driven pricing of transit services has proven elusive. 

2. There is some, albeit limited, interest in distance- and time-based fares, especially among agencies that have or soon will introduce smart cards. 

While scholars and researchers have long argued for transit pricing based on principles of economic efficiency, in practice, most agencies pursue fare policies that appear to favor administrative efficiency (e.g. keeping fare collection simple) and effectiveness (e.g. simple and low transit fares, unlimited use passes that reward frequent riders). Our survey results underscore that even with increasing technological ability to do so, a majority transit agencies are unlikely to implement distance-based or time-of-day pricing anytime in the near future. 

According to the American Public Transportation Association (APTA) (2012), 23 percent of transit operators nationwide currently employ some form of distance-based fare pricing and just 6 percent time of day pricing. While only 6 percent of the respondents to our survey who had recently adopted smart cards reported a move to time- or distance-based pricing as a result, nearly a quarter (24%) of those planning to adopt smart cards said that they expect to use them to implement some form of distance-based pricing, and fully 18 percent report the same for time-of-day pricing. This suggests that while resistance to variable pricing remains widespread, at least some of this resistance is likely due to the operational challenges of implementing differentiated pricing in the absence of smart cards. And as those operational vi challenges are reduced by smartcards, the longstanding trend away from differentiated fares may begin to reverse. 

3. Transit agencies are risk-averse and seek to minimize public scrutiny of any fare changes. 

Our survey results emphasize that transit officials seek to ensure their actions avoid public scrutiny and negative publicity, which substantially inhibits implementing variable cost pricing for two reasons. First, implementing variable fare pricing in almost all cases would be a radical departure from the flat fare status quo, and would thus subject a transit agency to financial scrutiny, heightened media attention, and increased lawmaker inquiry – all of which transit officials report they seek to avoid. Secondly, the transit managers we surveyed report that any fare increases will subject their agency to public scrutiny. Concerns over the negative consequences of fare changes appear to be so embedded that transit managers report focusing far more on the riders they might lose from any fare changes than the riders they might gain by implementing, for example, variable fares. They are, in other words, highly loss averse. Finally, the transit agency representatives we interviewed collectively reported that they have generally not conducted market research on non-riders or on customer responses to alternative fare structures, and that they have little understanding of the likely ridership gains and losses that might accompany distance- or time-based pricing. 

But despite the many potential benefits of marginal cost-based transit pricing touted in the literature, our interviews found significant evidence of risk-aversion, goal obfuscation, and cost confusion among transit managers, as predicted by the literature on public administration. The interviews revealed, with sometimes surprising candor, how little some senior transit managers understand their costs of service provision and how they vary. This lack of cost comprehension may be the inevitable result of government agencies’ mandate to maintain service without regard to cost or vice versa (Flam, Persson, and Svensson 1982). 

We hypothesize that transit agencies’ mission ambiguity is a leading explanatory factor of the context in which a poor understanding of costs can persist. As has been argued in the literature, this lack of cost comprehension is manifest in the crude ways in which transit fares are set, despite advances in technology that can facilitate a movement away from costabstracted, flat, and uniform fares and toward the cost-specific fares that vary based that cost of service provided. Our findings also suggest that the crisis-induced and budget-driven fare setting processes may be not the cause, but the effect of unclear or altogether absent goals. Even when a de facto pursuit of transit fare pricing effectiveness is evident, the absence of explicit goals to which agency decision-makers can refer, can mean that necessary, routine incremental fare increases are deferred until a distracting and destructive budgetary crisis forces a much larger and more disruptive fare increase on riders. 

This research suggests that transit agencies could avoid the contentious, fraught, and high-stakes “crises” that currently is all but a sine qua non for raising fares, while offering “fairer” fares that could increase ridership and revenue. However, the transit agency officials we interviewed reported having little information about whether such practices actually affect transit’s mode share. Several interviewees reported that they would expect to lose riders with any form of marginal-cost fare pricing, but had no idea whether or how they might gain additional riders under such a schema. Distance-based pricing, for example, could attract passenger for new, inexpensively priced short-trip riders who might have previously found $1.50 for a four block ride to be too much. The extent to which ridership would change depends on the urban context, economic conditions, traveler demographics, and so on; with information on these factors the ridership effects of fare structure changes could be estimated. Absent such information, any move to distance- or time-based pricing is a decidedly risky policy pursuit. 

Our interviewees also speculated that the larger the sources of operating and capital subsidies, the less likely it is that an agency’s managers will focus on farebox recovery ratios. This argument, echoed in the literature (Vrooman 1978; Flam, Persson, and Svensson 1982; Pickrell 1989), suggests that public subsidies have the perverse effect of reducing costefficiency and promoting subsequent budgetary crises. 

Transit officials also report that in a world where driving is cheap and preferred, transit officials have little choice but to maintain low fares in order to encourage mode shift. Given this unlevel playing field, then, the non-pursuit of marginal cost pricing may be reasonable to expect. But it also suggests that transit officials should support pricing policies such as congestion tolling and parking pricing, which help to internalize the costs of driving. However, our survey results show that transit officials tend to oppose, or are at best lukewarm toward, efforts to pricing the externalities of automobile travel. Just four in 10 of those surveyed support market-rate pricing on on-street parking, and just 27 percent support high occupancy/ toll (HOT) lanes; this contrasts dramatically with seven in 10 who support increased carpooling.

Cover page of The Quantified Traveler: Changing transport behavior with personalized travel data feedback

The Quantified Traveler: Changing transport behavior with personalized travel data feedback


Experiments using smartphones to influence behavior have been growing rapidly in many fields, especially in health and fitness research, and studies on eco-feedback technologies. In these studies, users are first tracked to understand their baseline behaviors, then measured continuously while they receive feedback about their actions. In transportation, studies using smartphones to change behavior have been limited due to the difficulty in even tracking users in the first place. Collecting data from smartphones in a battery efficient manner is a large research problem, and behavior change studies depend on being able to track travel behaviors. We developed an automated travel diary system which efficiently and uobtrusively collected travel data using smartphones and ran an experiment to evaluate how people’s awareness of their transportation behavior, attitudes towards sustainable transportation, intentions to change behavior, and measured travel behavior changed. For three weeks, 135 participants used an application on their iPhone or Android smartphone which unobstrusively tracked their location and sent data to a server which processed their data into trips and attributes related to their trips, such as time spent traveling, amount of money spent for transportation, amount of CO2 emitted, and calories burned during travel. Learning from prior work in eco-feedback studies and behavior change studies about health and fitness, a webpage was designed in which participants received feedback on their travel data along with trends and comparisons with various peer groups. Using surveys administered before and after the experiment, we measured a statistically significant change in partcipants’ awareness of statistics related to their travel behavior, and an intention to drive less and walk more amongst the “mainly-driving” group of the study population. In addition, a significant decrease in the amount of driving and increase in the amount of walking was measured. However, in a regression analysis, we were not able to find statistically significant covariates explaining what types of people and travelers were more likely to shift.

Cover page of Structural Equation Modeling For Travel Behavior Research

Structural Equation Modeling For Travel Behavior Research


Structural equation modeling (SEM) is an extremely flexible linear-in-parameters multivariate statistical modeling technique. It has been used in modeling travel behavior and values since about 1980, and its use is rapidly accelerating, partially due to the availability of imporved software. The number of published studies, now known to be more than fifty, has approximatley doubled in the pas three years. This review of SEM is intended to provide an introduction to the field for those who have not used the method, and the compendium of applications for those who wish to compare experiences and avoid the pitfall of reinventing previous research. 

Cover page of Downtown Parking and Traffic Congestion: A Diagrammatic Exposition

Downtown Parking and Traffic Congestion: A Diagrammatic Exposition


Through an extended numerical example, this paper develops a diagrammatic analysis of steady-state parking and traffic congestion in an isotropic downtown. The model incorporates curbside parking, garage parking, and price-sensitive travel demand in a unified setting, and provides systematic policy analysis. In particular, we examine the deadweight loss associated with underpriced curbside parking, as well as first- and second-best curbside parking capacities. We also explore the transient dynamics and stability of various downtown traffic equilibria.

Cover page of Traffic exposure near the Los Angeles-Long Beach port complex: using GPS-enhanced tracking to assess the implications of unreported travel and locations

Traffic exposure near the Los Angeles-Long Beach port complex: using GPS-enhanced tracking to assess the implications of unreported travel and locations


Traffic exposure assessments could misclassify the extent and locations of exposure if traditional recall surveys and self-reported travel diaries do not record all participant activities. The Harbor Communities Time Location Study (HCTLS) examines the nature, extent and implications of underreported locations/trips in a case study which used portable Global Positioning Systems (GPS) devices to track the diurnal patterns and traffic exposure of 47 residents of communities near the Los Angeles-Long Beach port complex. Participants were similar to adults nationwide in time spent indoors, in-vehicle, and outdoors, but spent more time indoors at home (78% vs. 66%). Overall, participants did not report nearly half (49%) of the locations and trips identified in GPS-enhanced data on their activity diaries, resulting in about 3 h/day in unreported locations and 0.6 h/day in unreported trips. The probability of a location/trip being under-reported was systematically correlated with participant and location/trip characteristics. Self-reported data missed about 50 min of heightened air pollution exposures during the 5 h/day on average participants spent in high-traffic areas and about 30 min during the 4 h/day near truck routes. GPS-enhanced methods provide opportunities to more precisely characterize exposure periods and tools to identify facility, roadway, and land use types of the greatest concern for mitigation efforts.