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Open Access Publications from the University of California

About

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.

Safe Transportation Research & Education Center

There are 153 publications in this collection, published between 2002 and 2019.
Research Reports (118)

Airports and Bicycles: what are the obstacles and incentives for operators 1 to improve bicycle access?

In this paper we use a case study approach to examine how airport operators are addressing bicycle access to their properties and the motivations and obstacles they face, in light of new policies to integrate bicycles, along with transit and walking, into transportation planning, design and construction, and to increase bicycles’ role in the transportation system.

Eight influential elements emerged from our review of policy documents and research literature. We used them to guide interviews with key informants. The eight elements are: governance structure, location, access roads, self-perceived environmental stewardship, spending restrictions on non-aviation transportation improvements, proximity to transit, policies and mandates to reduce environmental impacts and land use constraints. We report on seven cases, selected on the basis of inclusion in studies on key aspects of airport ground access and, for one, identification as exemplary. They are: Oakland International Airport, San Francisco International Airport, Los Angeles International Airport, Seattle-Tacoma International Airport, Boston Logan International Airport Minneapolis-St. Paul International Airport, and Portland, an exemplar recommended by several key informants. 

We limit our discussion to employee bicycle access because that has been the focus of airport operators that have made these investments and programs to reduce single-occupancy vehicle travel at airports.

In aggregating the interviews, we identified replicable approaches to improving bicycle access. We also identified examples of innovative funding for multi-modal access using revenues generated by airport Passenger Facilities Charges. Finally, we identified areas for additional research: airport employee commute needs, ground access mode choice and operator costs and benefits of bicycle access investments.

  • 1 supplemental PDF

Evaluation of Traffic and Environment Effects on Skid Resistance in California

Skid resistance is one of the important serviceability indicators related to safety on wet pavements. There is a need to manage skid resistance systematically to maintain the level of safety performance of roadway surfaces. This study focused on the development of a skid resistance deterioration model based on the analysis of skid data inventory collected in California. The California Department of Transportation (Caltrans) has collected skid resistance data across the complete state highway network over the past two decades using a standard locked-wheel skid trailer, ASTM E-274. This study utilizes skid data collected on more than 300 miles of asphalt concrete freeway in California over a period of twenty years. Most of the possible factors found in previous studies to influence skid resistance were considered. Panel data parameter estimation methods were used. The results indicate that factors with the largest effects on skid resistance are the age of pavement, ADT, temperature, precipitation, and the length of the period since the last significant precipitation.

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SafeTREC Webinars (25)

Methods and Technologies for Pedestrian and Bicycle Volume Data Collection

In this talk, an overview of the recently completed National Cooperative Highways Research Program project 07-19 will be presented. In NCHRP 07-19, research was conducted on a variety of methods and technologies for collecting bicyclist and pedestrian volume data. Research included a practitioner's survey, in-depth interviews with count program managers, and field testing and accuracy evaluation of six counting technologies. Counters were installed at roughly 15 different sites and evaluated for precision and reliability. The main product of this project is a guidebook on conducting counts of pedestrians and bicyclists, to be published in early 2015.

  • 1 supplemental PDF
  • 1 supplemental audio file

Frank Proulx, NCHRP 07-19: Methods and Technologies for Pedestrian and Bicycle Volume Data Collection

Abstract: In this talk, an overview of the recently completed National Cooperative Highways Research Program project 07-19 will be presented. In NCHRP 07-19, research was conducted on a variety of methods and technologies for collecting bicyclist and pedestrian volume data. Research included a practitioner's survey, in-depth interviews with count program managers, and field testing and accuracy evaluation of six counting technologies. Counters were installed at roughly 15 different sites and evaluated for precision and reliability. The main product of this project is a guidebook on conducting counts of pedestrians and bicyclists, to be published in early 2015.

  • 1 supplemental PDF
  • 1 supplemental audio file
22 more worksshow all
Working Papers (9)

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.

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. 

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. 

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