Training and education

Evaluation of Wet Weather Accident Causation Criteria

Oh, Soonmi
Ragland, David R.
Chan, Ching-Yao
2008

This report documents findings from analysis of traffic collision data from sites that display high collision rates only under wet pavement conditions. These sites were selected using Caltrans safety engineers’ field reports, Wet Table C “investigation required” locations, and a new approach called Continuous Risk Profile (CRP). The geometric features at the sites were studied via field visits and review of as-built plans. Rapid spatial changes (i.e., vertical and horizontal curve in short distance), narrower lane width, lack of median, and wider total freeway width were some of the...

Quantifying the Performance of Countermeasures for Collision Concentration Related to Ramp/Freeway Mainline Junctions

Lee, Joon Ho
Chan, Ching-Yao
Ragland, David R.
2009

This study performed before-and-after analyses (comparisons of collisions before and after the construction of auxiliary lanes) on collision rate at nine study sites in California in order to achieve two objectives: (i) to estimate the freeway Crash/Collision Reduction Factor (CRF) for auxiliary lanes, and (ii) to develop design guidelines for the construction of auxiliary lanes. Findings indicate that on average, collision rates decreased by 17.3 percent at nine study sites. The study also found that after construction of auxiliary lanes at two study sites, collision rates increased when...

Red-Light-Running Collision Avoidance

Grembek, Offer
Zhou, Kun
Zhang, Wei-Bin
2009

Red light running (RLR) problem has been recognized as a significant safety problem in California as well as throughout the United States. This paper follows a two step process to develop enhanced signal timing models for possible reduction of RLR. In the first step, field data are collected with one-second resolution and discrete choice models are estimated to determine the significant influencing factors of RLR; in the second step, based on the findings from the first step, T7F software package as well as custom designed programs is used to find the enhanced signal timing plans that can...

A Comparative Safety Study of Limited versus Continuous Access High Occupancy Vehicle (HOV) Facilities

Jang, Kitae
Ragland, David R.
Chan, Ching-Yao
2009
The report summarizes the findings from comparative studies of safety performance between two different types of High Occupancy Vehicle (HOV) facilities in California - continuous access versus limited access. The findings show that HOV facilities with limited access offer no safety advantages over those with continuous access, whether measured by percentage of collisions, collisions per mile, collisions per VMT, or collision severity. As part of the present research, the authors investigated the relationship...

Develop Methods to Reduce or Prevent Backing Crashes

Cooper, Douglas L.
Duffy, Sarah
Orrick, Phyllis
Ragland, David R.
2009

Workplace motor vehicle incidents at Caltrans are a significant cause of injuries, employee lost time, and property damage. Because backing crashes are major contributors to motor vehicle incidents, identifying and promoting methods of reducing backing accidents is a top priority. According to internal Caltrans’ data, 92.3% of workplace backing crashes were preventable by the driver. Backing crashes are the single largest category of preventable crashes, representing 30% of preventable crashes in the Caltrans fleet. From 1998 through 2007, preventable backing crashes cost Caltrans at least...

A Methodology for Counting Pedestrians at Intersections: Using Automated Counters to Extrapolate Weekly Volumes from Short Manual Counts

Schneider, Robert J.
Arnold, Lindsay S.
Ragland, David R.
2009

Accurate methods of counting pedestrians are needed to quantify exposure for safety analysis, rank infrastructure improvements and safety programs by priority, evaluate the benefits of pedestrian projects, develop models of pedestrian volumes, and track changes in pedestrian activity over time. However, pedestrian counts are still much less common than motor vehicle counts in most communities. In addition, existing count methodologies are not standardized and rarely provide enough information to extrapolate to weekly, monthly, or annual volumes. This exploratory study presents a...

Seamless Travel: Measuring Bicycle and Pedestrian Activity in San Diego County and its Relationship to Land Use, Transportation, Safety, and Facility Type

Jones, Michael G.
Ryan, Sherry
Donlon, Jennifer
Ledbetter, Lauren
Ragland, David R.
Arnold, Lindsay S.
2010

This paper provides the data collection and research results for the Seamless Travel project. The Seamless Travel Project is a research project funded by Caltrans and managed by the University of California Traffic Safety Center, with David Ragland, PhD., as the Principal Investigator and Michael Jones as the Project Manager. The project is funded by Caltrans Division of Innovation and Research and is being conducted by the Traffic Safety Center of University of California Berkeley and Alta Planning + Design. Measuring bicycle and pedestrian activity is a key element to achieving the goals...

Evaluation of Traffic and Environment Effects on Skid Resistance and Safety Performance of Rubberized Open-grade Asphalt Concrete

Oh, Soon Mi
Ragland, David R.
Chan, Ching-Yao
2010

Wet pavement-related collisions represent a significant traffic safety concern, due in part to the lack of adequate friction between tire and pavement, known as skid resistance. State agencies employ a skid number (SN) system, based on a standard test procedure in which a locked wheel is towed at 40 mph and the skid number (SN40) is calculated from the measured resistance. SN40 is used as a reference value for speeds both greater than and less than 40 mph. For most Departments of Transportation (DOTs) in the nation, excluding California, pavements for which the SN40 is below 30 are deemed...

Identifying Factors that Determine Bicycle and Pedestrian-Involved Collision Rates that Affect Bicycle and Pedestrian Demand at Multi-Lane Roundabouts

Arnold, Lindsay S.
Flannery, Aimee
Ledbetter, Lauren
Bills, Tierra
Jones, Michael G.
Ragland, David R.
Spautz, Laura
2010

This project examined the safety and demand issues for pedestrians and bicyclists at multi-lane roundabouts through a literature review, case studies, in-field counts and surveys, focus groups, and video analysis. This document presents research findings, synthesizes current information on best practices, and makes recommendations to assist local agencies planning and designing safer multi-lane roundabouts. These findings should help local agencies and Caltrans create roundabouts that better and more safely address the needs of bicyclists and pedestrians. The current literature is referred...

Geocoding vehicle collisions on Korean expressways based on postmile referencing

Park, Shin Hyoung
Bigham, John M.
Kho, Seung-Young
Kang, Seungmo
Kim, Dong-Kyu
2011

Geocoding is the process of assigning latitude and longitude coordinates to data that contain spatial information. Geocoded records of motor vehicle collisions are an invaluable resource for injury prevention researchers. The objective of this study is to apply the postmile referencing system for geocoding collisions on Korean expressways and summarize the methodology and results with comparative research efforts in the USA. A street network provided by Korea Expressway Corporation was cleaned and calibrated using ArcGIS and a customized Visual Basic for Applications (VBA) tool....