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Open Access Publications from the University of California

The Safe Transportation Research and Education Center (SafeTREC) mission is the reduction of transportation-related injuries and fatalities through research, education, outreach, and community service.

Founded in 2000 as the Traffic Safety Center (TSC), the Center was renamed in 2009 to more accurately reflect the mission to encompass safety and travel risk in a multimodal transportation system; a robust and diverse research agenda across multiple disciplines; and development and enhancement of curriculum, training, and outreach on the graduate and undergraduate levels, as well as for professionals and members of the community.

SafeTREC is part of the University of California, Berkeley, and is affiliated with the School of Public Health and the Institute of Transportation Studies, with additional partnerships with the Department of City and Regional Planning, Public Policy, and Transportation Engineering. Our research is carried out by faculty at UC Berkeley with assistance from post-doctoral scholars, research staff, and graduate student researchers. We also help the California Office of Traffic Safety administer its Community Pedestrian and Bicycle Safety Training workshops and support various safety initiatives from other California agencies, Including the California Department of Transportation (Caltrans).
SafeTREC's three emphasis areas are:

Data Analysis and Data Tools is a necessity for understanding safety/mobility in transportation / land use planning in California.  SafeTREC will build on current large scale data efforts (geocoding 15 years of traffic crashes in California, adding pedestrian and bicycle infrastructure elements to the State Highway data base, building a statewide Tribal Road Safety Data Base) to construct state-of-the-art data analysis and mapping tools for use by government agencies, researchers, and the general public.

Technology for Road Safety, including crash warning and avoidance systems, smart infrastructure sensing systems, and automated vehicles. SafeTREC will be in the forefront of evaluating the benefits and costs of these rapidly emerging technologies. This emphasis area will also utilize technology for in-depth analysis of crash reports, data visualization techniques, and developing novel transportation safety management methods.

Policy Analysis and Community Outreach will continue to be a necessity to connect with California’s extremely diverse communities to improve road safety and encourage active transportation. SafeTREC will build on existing policy analyses (e.g., Safe Routes to School) and community outreach (e.g., Community Pedestrian and Bicycle Safety Training, data analyses and presentations for local governmental agencies) to create a national model for policy analysis and community outreach.

Cover page of Emergency Medical Services (EMS) and the California EMS Information System (CEMSIS) Working Paper

Emergency Medical Services (EMS) and the California EMS Information System (CEMSIS) Working Paper


This study examines data from the California EMS Information System (CEMSIS) to identify factors that influence prehospital time for EMS events related to motor vehicle collisions (MVCs). While only 19 percent of the United States population resides in rural areas, over half of all traffic fatalities involve rural motor vehicle collisions. Rural and urban MVCs result in similar injury severities, however relative inaccessibility of trauma centers and prehospital EMS time (activation, response, and transport time) likely contribute to the generally higher mortality rate in rural areas. For the present study, 24 CEMSIS data variables were requested, many of which involved missing data, which severely restricted the potential analysis of the impact of EMS response times. However, the findings did show that average overall EMS time (including response, scene and transport time) were approximately twice as long for collisions in rural zip codes compared with urban zip codes. Several limitations influence the interpretation of these results. Data on prehospital EMS times is missing for much of the state—even for zip codes with records of EMS events, data is likely incomplete. In addition, zip code level location data is insufficient for adequate study of the effects of the built environment and road network on prehospital time. Furthermore, according to the National EMS Information System (NEMSIS) User Manual, the national dataset suffers from selection and information bias, which are likely also present in the CEMSIS data. Although the present study cannot analyze the effect of longer prehospital times on patient outcome, other research has found that longer prehospital times may negatively impact patient health. Recommendations for reducing time from injury to appropriate medical care in rural areas include improving cell phone coverage, compliance of rural 911 center with FCC wireless, use of GPS technology, and integration of automatic vehicle location and computer aided navigation technologies into all computer-aided dispatch systems. In addition, CEMSIS should improve the coverage of their dataset and ensure that all EMS activities are recorded. To expand the type of analyses that can be conducted using CEMSIS data, EMS records must include fields that allow them to be linked to hospital and police datasets. When such data becomes available, research must be conducted to determine whether prehospital time is significantly related to patient outcome following motor vehicle collisions.

Cover page of Do All Roadway Users Want the Same Things?

Do All Roadway Users Want the Same Things?


This paper presents findings from a recent study on roadway design preferences among pedestrians, drivers, bicyclists, and public transit users along a major urban corridor in the East San Francisco Bay Area.  Sponsored by the California DOT, the research focused on exploring design preferences that could increase perceived traffic safety, walkability, bikability, and economic vitality along urban arterials.  

Results from an intercept survey showed that all user groups desire similar roadway design features along the test corridor, which carries 25,000-30,000 motorists bi-directionally and has comprehensive sidewalk coverage, but no bicycle facilities.  In an open-ended question about street improvements to enhance perceived traffic safety, all respondent groups requested the same top five improvements.  Bicycle lanes were ranked first by pedestrians, drivers, and bicyclists (fifth by public transit respondents), and improved pedestrian crossings were ranked second by pedestrians, drivers, and public transit users (third by bicyclists).  The other top five suggestions were the same for all groups, though ordered slightly differently: slowing traffic/improving driver behavior, increasing street lighting, and increasing traffic signals/stop signs. Similar preference alignment was found regarding street improvements to encourage more visits to the corridor. 

These findings suggest that design features generally thought to benefit one road user group, such as bicycle lanes for bicyclists, may also benefit other users.  Moreover, these results provide evidence that roadway planning can take advantage of synergistic opportunities to benefit multiple user groups by implementing a few key design interventions.  Overall, the findings support the continued implementation of complete streets principles and policies.

Cover page of Low Cost Upgrades to At-Grade Crossing  Safety Devices

Low Cost Upgrades to At-Grade Crossing Safety Devices


The only way to absolutely prevent all drivers from going around lowered gates at level rail-highway crossings is to make it physically impossible, or at least very difficult, for them to do so. While there are various options to accomplish this (constructing a separation of grade, closing the crossing, or deploying an impenetrable concrete barrier), most have high monetary or social costs. Alternative approaches—such as channelization devices and long-arm gates—while not 100 percent effective, can be used to prevent deaths and injuries while remaining economically feasible. Research has shown that the addition of channelization devices can dramatically reduce the number of violations at level rail-highway crossings. While long-arm gates appear to be effective, additional study is needed to determine their suitability for individual locations. Unfortunately, even when overall rail crash totals for the country or for a given state are high, crashes at specific crossings are relatively rare events, making it extremely difficult to show that the addition of a safety treatment at a particular site prevented a crash. However, based on the efficacy of channelization devices—75 percent—in addition to the experiences of various transportation agencies, these devices appear to be a viable, low cost safety upgrade for at-grade crossings.

Cover page of Roadway and Infrastructure Design and Its  Relation to Pedestrian and Bicycle Safety:  Basic Principles, Applications, and Benefits

Roadway and Infrastructure Design and Its Relation to Pedestrian and Bicycle Safety: Basic Principles, Applications, and Benefits


Road deaths are forecast to double by 2020, with the burden falling most heavily on low- and middle-income countries and, within those countries, on the most vulnerable and poorest road users. Half of the 1.2 million people killed and 50 million injured in road crashes each year are pedestrians, motorcyclists, bicyclists, and users of unsafe public transport; and more than 90 percent are from low- and middle-income countries. Because these are the areas where rapid motorization is taking place, the issue of safety in increasingly multi-modal environments is now of critical importance, particularly for pedestrians and bicyclists, since as vulnerable road users (VRU), they comprise a large proportion of injuries and deaths, and similar strategies for prevention of injuries and fatalities for these two groups are available. Although a great deal of additional research is needed to determine the costs and benefits of various proposed solutions, some basic principles can be identified to guide roadway and infrastructure design for improved pedestrian and bicyclist safety. The three broad but separate strategies for reducing the probability of an injury or fatality are: (i) reducing exposure, (ii) reducing the probability of a collision given exposure, and (iii) reducing the probability of injury given a collision. The purpose of this paper is to describe and illustrate these principles, discuss issues related to each one, and discuss the benefits—indeed, imperativeness—of the application of these principles by planners and traffic engineers.

Cover page of Documenting Targeted Behaviors Associated with Pedestrian Safety

Documenting Targeted Behaviors Associated with Pedestrian Safety


The purpose of this study is to provide an exploratory analysis of the proportion of pedestrians, bicyclists, and drivers exhibiting four specific behaviors at 12 intersections near transit stations in 4 the San Francisco Bay Area. The target behaviors include: 1) pedestrians crossing the roadway while using a mobile device, such as a cell phone, 2) pedestrians crossing a signalized intersection against a red light, 3) bicyclists running a red light at a signalized intersection, and 4) automobiles turning right on red without stopping. These four behaviors are important because they may lead 8 to pedestrian crashes. Field observations show a range of observed pedestrian and bicycle violation of red lights. At some locations as few as 2.4% of non-motorized road users violated red lights, whereas 40% did at other sites. The range of vehicles violating red lights was somewhat higher, with 20% to 62% of drivers turning right illegally on a red light. Male pedestrians were more likely than females to talk on mobile devices while crossing the street and crossing the street at red lights. As pedestrian and bicycle mode shares increase, it will be essential for all users to understand their rights and responsibilities in the roadway environment. Documenting behaviors helps provide a foundation for engineering, education, and encouragement treatments that will improve safety for pedestrians and other roadway users. 

Cover page of Development and Application of the San Francisco Pedestrian Intersection Volume Model

Development and Application of the San Francisco Pedestrian Intersection Volume Model


The San Francisco pedestrian volume modeling process refined the methodology used to develop previous intersection-based models and incorporated variables that were tailored to estimate walking activity in the local urban context. The methodology included two main steps. First, manual and automated pedestrian counts were taken at a sample of 50 study intersections with a variety of characteristics. A series of factor adjustments were applied to produce an annual pedestrian crossing estimate at each intersection. Second, log-linear regression modeling was used to identify statistically-significant relationships between the annual pedestrian volume estimate and land use, transportation system, local environment, and socioeconomic characteristics near each intersection. Twelve alternative models were considered, and the preferred model had a good overall fit (adjusted-R 2= 0.804). As identified in other communities, pedestrian volumes were positively associated with the number of households and the number of jobs near each intersection. Uniquely, this San Francisco model also found significantly higher pedestrian volumes at intersections in high-activity zones with metered on-street parking, in areas with fewer hills, near university campuses, and controlled by traffic signals. The model was based on a relatively small sample of intersections, so the number of significant factors was limited to six. Results are being used by public agencies in San Francisco to better understand pedestrian crossing risk and to inform citywide pedestrian safety policy and investment.

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Cover page of Missed or Delayed Medical Care Appointments by Older Users of Nonemergency Medical Transportation Services

Missed or Delayed Medical Care Appointments by Older Users of Nonemergency Medical Transportation Services


Non-emergency medical transportation (NEMT) can prevent emergency care as a result of delayed or missed medical appointments. Medicaid provides NEMT for low income individuals who have no other means of transportation and this is a critical component of the health care delivery system. This study examined cancelled trips in Medicaid adults age 65+ to explore whether barriers persist for a growing segment of the population who face particular challenges of age-related declines in health and function. Multivariate logistic regression analyses were conducted using transportation brokerage data for Delaware members who intended to travel during 2008-2010, modeling the odds of all cancellations and then these mutually exclusive types: (1) client cancelled; (2) client obtained alternative transportation; and (3) client cancelled due to health. Over half of the cancelled trips were attributed to client reasons. Black race was associated with client canceling (OR=1.4) and canceling due to alternative transportation (OR=1.9). Compared to dialysis, trips for other medical care were more likely to be cancelled for client and health reasons (ORs ranged 1.6-7.9). Higher levels of service increased cancelling for health reasons (OR=2.9 stretcher; OR=1.8 wheelchair). Finally, pre-scheduled or subscription trips were less likely to be cancelled and client factors differed for the cancellation of trips that were not regularly scheduled. The results of this initial study confirm that for this population additional transportation services are often not available and that more support for utilizing NEMT may be needed. Future research should evaluate persistent barriers, service delivery, and long-term outcomes. 

Cover page of How Common is Pedestrian Travel To, From, and Within Shopping Districts?

How Common is Pedestrian Travel To, From, and Within Shopping Districts?


Growing interest in sustainable transportation systems and livable communities has created a need for more complete measures of pedestrian travel. Yet, many performance measures do not account for short pedestrian movements, such as walking between stores in a shopping district, walking from a street parking space to a building entrance, or walking from a bus stop to home. This study uses a 2009 intercept survey and the 2009 National Household Travel Survey to quantify pedestrian travel to, from, and within 20 San Francisco Bay Area shopping districts. Overall, walking was the primary travel mode for 21% of intercept survey and 10% of NHTS tours with stops in these shopping districts. However, detailed analysis of pedestrian movements showed that walking was common on respondent tours (52% of intercept survey tours included some walking) and that walking was used on the majority of trips within these shopping districts (65% of intercept survey trips and 71% of NHTS trips within the shopping districts were made by walking). In general, Urban Core and Suburban Main Street shopping districts had higher levels of pedestrian activity than Suburban Thoroughfare and Suburban Shopping Center shopping districts. The detailed analysis in this paper provides a more complete picture of pedestrian activity than is commonly shown by national and regional household survey summaries.