Training and education

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...

The Continuing Debate about Safety in Numbers—Data from Oakland, CA

Geyer, Judy A.
Raford, Noah
Ragland, David R.
Pham, Trinh
2006

The primary objective of this paper is to review the appropriate use of ratio variables in the study of pedestrian injury exposure. We provide a discussion that rejects the assumption that the relationship between a random variable (e.g., a population X) and a ratio (e.g., injury or disease per population Y/X) is necessarily negative. In the study of pedestrian risk, the null hypothesis is that pedestrian injury risk is constant with respect to pedestrian volume. This study employs a unique data set containing the number of pedestrian collisions, average annual pedestrian volume, average...

High Collision Concentration Location: Table C Evaluation and Recommendations

Ragland, David R.
Chan, Ching-Yao
2007

This report describes the research work that was conducted under PATH Task Order 5215 and its extension Task Order 6215, “Methods for Identifying High-Concentration Collision Locations (HCCL).” The subject matter is related to regularly published Caltrans reports, so-called Table C, that are used to screen for and investigate locations within the California State Highway System that have collision frequencies significantly greater than the base or expected numbers when compared to other locations. The accuracy and reliability of such reports are critical as Table C is the basis for follow-...

Driver/Pedestrian Understanding and Behavior at Marked and Unmarked Crosswalks

Ragland, David R.
Mitman, Meghan F.
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...

Space Syntax: The Role of Urban Form in Cyclist Route Choice in Central London

Raford, Noah
Chiaradia, Alain
Gil, Jorge
2007

This paper presents a new method for forecasting cyclist volume and route choice based on space syntax techniques for urban analysis. Space syntax has been shown to correlate strongly with pedestrian and vehicular trips in a number of international studies, but little research to date has focused on the role of urban form and street network design in cyclist route choice. This paper addresses this gap by analyzing the distribution of cycling trips in the central London area, focusing on a sample of work-based commuting trips. A sample of 423 cyclists from 50 organizations was combined with...

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-bycity assessment of FDW intervals on the SPA corridor. We suggest a possible tool to assist traffic control...

What They Don’t Know Can Kill Them

Mitman, Meghan F.
Ragland, David R.
2007

Traffic safety researchers have long argued that driver behavior outweighs physical elements (such as road design) as a causal factor in motor vehicle collisions. A fundamental causal component of pedestrian-vehicle collisions is also behavior—that of the driver and that of the pedestrian. One determinant of this behavior may be whether the driver, the pedestrian, or both understand the motor vehicle code, which demarcates right-of-way in pedestrian-vehicle interactions. That is, inappropriate or unlawful behavior may occur because the law is not understood or is misunderstood. Previous...

Changes in Driver Behavior Resulting from Pedestrian Countdown Signals

Huey, S. Brian
Ragland, David R.
2007

This paper explores the effects that pedestrian countdown signals have on driver behavior. Observations of two intersections, one with pedestrian signals and one without, were made focusing specifically on driver behavior during the amber and red phases. It was found that drivers at the pedestrian countdown intersection were less likely to enter the intersection at the end of the amber phase than those at the traditional pedestrian signal intersection. It was also found that drivers at the intersections with traditional pedestrian signals exhibited different stopping behavior near the...

Pedestrian Counting Methods at Intersections: a Comparative Study

Diogenes, Mara Chagas
Greene-Roesel, Ryan
Arnold, Lindsay S.
Ragland, David R.
2007

Resources for implementing countermeasures to reduce pedestrian collisions in urban centers are usually allocated on the basis of need, which is determined by risk studies. They commonly rely on pedestrian volumes at intersections. The methods used to estimate pedestrian volumes include direct counts and surveys, but few studies have addressed the accuracy of these methods. This paper investigates the accuracy of three common counting methods: manual counts using sheets, manual counts using clickers, and manual counts using video cameras. The counts took place in San Francisco. For the...

Rail Crossings: A Strategy to Select Countermeasure Improvements for Rail-Highway Crossings in California

Cooper, Douglas L.
Ragland, David R.
2007

Rail crossing crashes have declined in the past 30 years, both nationally and in California. This is largely attributed to the closing of a large number of crossings as well as the deployment of a wide range of countermeasures, including signal systems, gating and grade separation programs. However, the number of crashes and subsequent injuries and deaths is still unacceptably high. Rail crossings provide different levels of warnings from four-quadrant gates down to stop signs. To understand how the state of California can best utilize state and federal funding available through SAFETEA-LU...