Roads/Highways

Single-Vehicle Fatal Crash Prediction for Two-Lane Rural Highways in the Southeastern United States

Zhu, Hong
Dixon, Karen K.
Washington, Simon
Jared, David M.
2010

The rural two-lane highway in the Southeastern United States is frequently associated with a disproportionate number of serious and fatal crashes and as such remains a focus of considerable safety research. The Georgia Department of Transportation spearheaded a regional fatal crash analysis to identify various safety performances on two-lane rural highways and offer guidance for identifying suitable countermeasures to mitigate fatal crashes. The fatal crash data used in this study were compiled from Alabama, Georgia, Mississippi, and South Carolina. The database, developed for an earlier...

Providing Intersection Decision Support under Challenging Conditions

Shladover, Steven E.
VanderWerf, Joel
Ragland, David R.
2006

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...

Safety Performance of Experimental Pavement Types in California Using Before-and-After Comparisons

Oh, Soonmi
Ragland, David R.
Chan, Ching-Yao
2010

This study focused on safety performance of new pavement surface types. Open graded or coarse-textured roadway surfaces are advisable for high-speed, wet-weather traffic conditions. They provide drainage relief at the tire-pavement interface, reduce the steepness of the speed gradient, decrease the likelihood of hydroplaning, minimize splash and spray, reduce the glare from wet pavements, and improve high-speed skid resistance. Before-and-after comparisons using historical collision data from California Traffic Accident Surveillance and Analysis System (TASAS) were conducted to assess the...

San Pablo Avenue Pedestrian Signal Timing Optimization

Nguyen, Ahn
Ragland, David R.
2007

The focus of this study is to quantify the sufficiency of “Flashing Don’t Walk” (FDW) intervals at signalized pedestrian crossings in the San Pablo Avenue (SPA) corridor in Northern California. Our goal is to determine if pedestrian signal intervals on the SPA corridor can be optimized in a way that makes the pedestrian crossing environment safer and more comfortable for all pedestrians without diminishing vehicular throughput. This study provides a corridor-wide as well as a city-by-city assessment of FDW intervals on the SPA corridor. We suggest a possible tool to assist traffic control...

Applying Safety Treatments To Rail-Highway At-Grade Crossings

Cooper, Douglas L.
Ragland, David R.
2012

At-grade rail crossings provide different levels of warnings and/or barriers to alert drivers to the potential dangers presented by approaching trains. For some drivers, an activated warning system, rather than being a signal to stop, merely serves as a cue for the need to make a decision whether or not to cross. In California, for the ten-year period from 2001 to 2010, the result was 1,033 trainvehicle crashes resulting in 157 deaths and 458 injuries. The best solution to rail crossing crashes is to remove the need for the driver to engage in a potentially faulty decision-making process...

The Continuous Risk Profile Approach for the Identification of High Collision Concentration Locations on Congested Highways

Chung, Koohong
Ragland, David R.
Madanat, Samer
Oh, Soon Mi
2009

This paper documents a new method for monitoring traffic collision data from continuous roadway facilities to detect high collision concentration locations. Many existing methods for detecting collision concentration locations require segmentation of roadways and assume traffic collision data are spatially uncorrelated, resulting in both false positives (i.e., identifying sites for safety improvements that should not have been selected) and false negatives (i.e., not identifying sites that should have been selected). The proposed method does not require segmentation of roadways; spatial...

Impact of Traffic States on Freeway Collision Frequency

Yeo, Hwasoon
Jang, Kitae
Skabardonis, Alexander
2010

Freeway collisions are thought to be affected by traffic states. To reduce the number of collisions, the study to reveal how the traffic states influence collisions are required. Therefore, the purpose of the paper is to suggest a method to relate traffic states to collision frequency in freeway. We first defined section- based traffic phases showing traffic state of a section using upstream and downstream traffic states: free flow (FF), back of queue (BQ), bottleneck front (BN) and congestion (CT). Secondly, by integrating freeway collision data and traffic data from the California PeMS...

Driver/Pedestrian Understanding and Behavior at Marked and Unmarked Crosswalks

Ragland, David R.
Mitman, Meghan Fehlig
2007

Pedestrian injuries at crosswalk locations represent a significant problem. In 2002, 22.7 percent of US pedestrians involved in collisions were in a crosswalk at the time of the collision, and over 96% of these occurred at an intersection. Almost all crosswalk collisions resulted in pedestrian injury or fatality (98.6 percent), and about one-third resulted in severe or fatal injury (National Automotive Sampling System (NASS) and General Estimates System (GES) 2002). As the owner of the California State Highway System, Caltrans is responsible for providing access to safe and convenient...

Safety Performance of High-Occupancy Vehicle (HOV) Facilities: Evaluation of HOV Lane Configurations in California

Jang, Kitae
Chung, Koohong
Ragland, David R.
Chan, Ching-Yao
2009

Collision data from High Occupancy Vehicle (HOV) facilities with two different types of access, continuous and limited, are examined in this paper. The findings show that HOV facilities with limited access offer no safety advantages over those with a continuous access. Compared with continuous access HOV lanes, a higher percentage of collisions was concentrated on limited access HOV lanes. Limited access HOV lanes also had higher collision rates. Findings from investigating the relationship between collision rates in HOV lanes with respect to shoulder width, length of access, and the...

Building a Highway Linear Referencing System from Preexisting Reference Marker Measurements for Transportation Data Management

Bigham, John
Kang, Sanghyeok
2013

To manage events associated with highways, data systems have been developed to store relevant event information. To reap the full benefits of geographic information system technologies, the relative locations can be integrated into a linear referencing system. The objective of this paper is to present a methodology for building a highway linear referencing system by applying preexisting marker measurements to a digital street network. The system was developed for locating motor vehicle collisions in California and resulted in improved accuracy compared to a previously developed system....