Road User Behavior

SafeTREC director Julia Griswold presents to California Senate on how to address systemic risk in our transportation system

March 20, 2026
Submitted by Kris Leckie
Earlier this month, SafeTREC director Julia Griswold presented at a joint Senate informational hearing in Sacramento, convened by California State Senators Dave Cortese (D-San Jose) and Jesse Arreguín (D-Oakland), chairs of the Transportation Committee and Public Safety Committee respectively....

California Traffic Safety Survey 2023

Ewald, Katrin
Wasserman, Lisa
2023

Similar to the survey waves since 2020, the 2023 California Traffic Safety Public Opinion Study was conducted by Ewald & Wasserman Research (E&W) on behalf of the California Office of Traffic Safety (OTS) and the Safe Transportation Research and Education Center of UC Berkeley (SafeTREC), with an online self-administered survey. Survey panelists were provided through Marketing Services Group, a commercial sample and panel vendor.

The eligibility criteria for participating in the study were possessing a valid California driver’s license and being 18 years or older. Eligible...

Pre-hospital Care of Road Traffic Injuries in Chiang Mai, Thailand

Brown, Ted R.
Geyer, Judy A.
Taghavy, Azita
Mitchell, Brian P.
Ragland, David R.
2004

In many developing countries, transportation infrastructure development lags behind the tremendous growth in motorization. Road traffic injuries cause enormous morbidity and mortality worldwide, placing heavy burdens on global and national economies. Underdeveloped transportation infrastructures critical to traffic safety include roadway improvement, occupant protection laws, traffic law enforcement, and emergency medical services (EMS). Highlighting one important aspect of lagging infrastructure, this article focuses on emergency medical services. This research study offers a descriptive...

Impact of Pedestrian Presence on Movement of Left-Turning Vehicles: Method, Preliminary Results & Possible Use in Intersection Decision Support

Banerjee, Ipsita
Shladover, Steven E.
Misener, James A.
Chan, Ching-Yao
Ragland, David R.
2004

Warning systems are being developed for left-turning vehicles at intersections where protected left-turns are not warranted or cannot be provided, based on limitations of right of way or intersection capacity. These are meant to provide warnings to left-turning vehicles of vehicles approaching from the opposite direction, when the time to turn may be deemed unsafe. To implement these warning systems, it is necessary to estimate in near real time, the probability of conflict between the two approaching vehicles. A study is being conducted with the help of video and radar at various...

Alcohol, Stress-Related Factors, and Short-Term Absenteeism Among Urban Transit Operators

Cunradi, Carol B.
Greiner, Birgit A.
Ragland, David R.
Fisher, June M.
2005

Transit operators, relative to workers in many other occupations, experience high levels of work-related stress, as documented through neuroendocrine elevations on the job vis-à-vis resting states (J Occup Health Psychol. 1998;3:122–129). Previous research suggests that self-reported job stress is associated with higher levels of alcohol consumption among transit operators (Alcohol Clin Exp Res. 2000;24:1011–1019) and with absenteeism (Working Environment for Local...

Pedestrian and Bicycle Safety Evaluation for the City of Emeryville at Four Intersections

Johnson, Emily S.
Ragland, David R.
Cooper, Jill F.
O'Connor, Terri
2005

The City of Emeryville is small in area (1.2 square miles) and population (7,000), but it is one of the most regionally connected cities in the Bay Area (California). Emeryville is situated at the eastern end of the San Francisco-Oakland Bay Bridge, contains the intersection of Interstate Highway 80 (I-80) with several regional and other interstate highways, and has extensive transportation access by Amtrak Rail, Alameda County (AC) Transit and heavy cargo facilities at the nearby Port of Oakland. The city has many large employers and several large shopping areas, and the daytime...

Attributable risk of alcohol and other drugs for crashes in the transit industry

Cunradi, Carol B.
Ragland, David R.
Greiner, Birgit A.
Klein, M.
Fisher, June M.
2005

Objective: To estimate the impact of employee alcohol and drug use on crashes in the transit industry from 1995–2000.

Design: Secondary analysis of federally mandated post crash and random alcohol and drug testing results.

Setting: The US transit industry.

Subjects: Transit industry employees.

Main outcome measures: Relative risk (RR), population attributable risk (PAR), and population attributable risk percentage (PAR%).

Results: For alcohol testing, the estimated PAR% ranged...

Pedestrian Volume Modeling for Traffic Safety and Exposure Analysis: The Case of Boston, Massachusetts

Raford, Noah
Ragland, David R.
2005

This paper examines three types of pedestrian volume models in light of their usefulness for estimating pedestrian exposure for pedestrian safety research. The need for pedestrian flow data as part of pedestrian exposure and safety analysis is outlined, and the background of each type of model is discussed. It then selects the space syntax network analysis model to estimate pedestrian volumes for the city of Boston, Massachusetts. It was found that the model was able to accurately predict pedestrian flows (r-squared 0.81, p-value < 0.0001) after incorporating distance to transit stops...

Providing Intersection Decision Support under Challenging Conditions

Shladover, Steven E.
VanderWerf, Joel
Ragland, David R.
2005

This paper describes the results of simulation studies to determine how effectively left-turning drivers can be alerted to imminent conflicts with opposing traffic under difficult operating conditions and with limited detector capabilities. These conditions include approaching vehicles changing speed in locations that are not covered by detectors and detectors that may only be able to detect vehicle presence, but not speed. In cases without direct speed detection, one may try to rely on historical speed statistics to estimate the speed of approaching traffic, but unless the approach speeds...

Gap acceptance for vehicles turning left across on-coming traffic: Implications for Intersection Decision Support design

Ragland, David R.
Arroyo, Sofia
Shladover, Steven E.
Misener, James A.
Chan, Ching-Yao
2005

A left-turning vehicle (Subject Vehicle, SV) attempting to cross the path of an oncoming vehicle (Principal Other Vehicle, POV) at an intersection typically does not have the right of way. The main task of the SV driver is to find an adequate opportunity in opposing traffic to initiate the left-turn maneuver. To reduce the probability of a conflict, warning systems, such as Intersection Decision Support (IDS) systems, are being developed. These systems alert drivers of SV vehicles attempting to negotiate a left turnabout traffic approaching from the opposite direction. The current...