Data collection

Estimating Pedestrian Accident Exposure: Protocol Report

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

Walking is a healthful, environmentally benign form of travel, and is the most basic form of human mobility. Walking trips account for more than 8 percent of all trips taken in California, making walking the second most commonly used mode of travel after the personal automobile (Caltrans, 2002). In addition, many trips made by vehicle or public transit begin and end with walking.

In spite of the importance and benefits of walking, pedestrians suffer a disproportionate share of the harm of traffic incidents in California. As noted above...

Integration of Light Rail Transit into City Streets

Korve, Hans W.
Farran, Jose I.
Mansel, Douglas M.
Levinson, Herbert S.
Chira-Chavala, T.
Ragland, David R.
1996

This report addresses the safety and operating experience of light rail transit (LRT) systems operating in shared (on-street or mall) rights-of-way at speeds that do not exceed 35 mph. It is based on agency interviews, field observations, and accident analyses of 10 LRT systems in the United States and Canada. These systems—in Baltimore, Boston, Buffalo, Calgary, Los Angeles, Portland, Sacramento, San Diego, San Francisco, and San Jose—provide a broad range of current LRT operating practices and problems.

The report provides information to facilitate the safe, orderly, and...

Relative Vulnerability Matrix for Evaluating Multimodal Traffic Safety

Grembek, Offer
2015

The multimodal transportation network includes a mix of inherently different modes. In addition to differences in price, range, and comfort of travel, these modes differ in mass and velocity, which correspond to different orders of magnitude in the kinetic energy carried. This discrepancy in kinetic energy affects both the level of protection of each mode, and the level of damage it can inflict on users of other modes. Unfortunately, accounting for both sides of a crash is often overlooked. While the quantities and variables of collected data continue to increase, the analyses conducted...

Using Variable Speed Limits To Reduce Rear-End Collision Risks Near Recurrent Bottlenecks

Li, Zhibin
Liu, Pan
Bigham, John M.
Ragland, David R.
2013

Rear-end collisions would occur if vehicle speeds decrease abruptly when encountering kinematic waves (KWs) emanating from active bottlenecks. This study aims to develop a control strategy in variable speed limits (VSL) to reduce rear-end collision risks near recurrent bottlenecks. Using the crash prediction model developed for rear-end collisions related to risky KWs, the effectiveness of VSL control strategies were evaluated in the cell transmission model (CTM). Several strategies were tested in sequence to determine the best case for risk reduction. Results of this study show that the...

Acceptance of drinking and driving and alcohol-involved driving crashes in California

MacLeod, Kara E.
Karriker-Jaffe, Katherine J.
Ragland, David R.
Satariano, William A.
Kelley-Baker, Tara
Lacey, John H.
2015

Background: Alcohol-impaired driving accounts for substantial proportion of traffic-related fatalities in the U.S. Risk perceptions for drinking and driving have been associated with various measures of drinking and driving behavior. In an effort to understand how to intervene and to better understand how risk perceptions may be shaped, this study explored whether an objective environmental-level measure (proportion of alcohol-involved driving crashes in one’s residential city) were related to individual-level perceptions and behavior.

Methods: Using data from a 2012 cross-sectional...

Crashes on and Near College Campuses: A Comparative Analysis of Pedestrian and Bicyclist Safety

Loukaitou-Sideris, Anastasia
Medury, Aditya
Fink, Camille
Grembek, Offer
Shafizadeh, Kevan
Wong, Norman
Orrick, Phyllis
2014

Problem, research strategy, and findings: College campuses are multimodal settings with very high levels of walking and biking in conjunction with high levels of vehicular traffic, which increases risks for bicyclists and pedestrians. In this study, we examine crash data (both police reported and self-reported) and urban form data from three U.S. campuses to understand the spatial and temporal distribution of crashes on the campuses and their immediate periphery. To account for underreporting of pedestrian and bicycle crashes, we developed and circulated an online survey, which helped...

The Impact of Health Problems on Driving Status Among Older Adults

MacLeod, Kara E.
Satariano, William A.
Ragland, David R.
2014

Objective: This study assessed the impact of health problems on driving status (current driver vs. ex-driver) among older adults to identify which of those health problems have the greatest individual and population impact on driving cessation.

Methods: Data were from baseline and a 5 year follow-up wave of a longitudinal survey of adults aged 55 years and older (N¼1279). The impact of several health problems on driving status was assessed using a relative risk ratio and a population attributable risk percent. Analyses controlled for age, gender, and the presence of additional...

Associations between Road Network Structure and Pedestrian-Bicyclist Accidents

Zhang, Yuanyuan
Bigham, John M.
Li, Zhibin
Ragland, David R.
Chen, Xiaohong
2012

It is widely known that the road network layout can impact the non-motorized users’ traffic safety by changing the non-motorized traffic volume and road users’ behavior. Different road network patterns lead to different traffic safety levels for non-auto users and a single pattern can even have both the safe and unsafe features at the same time. By knowing what features can lead to safer traffic environment, existing road networks can be improved and new network patterns can be produced by combining all safe features from different patterns. Therefore, the associations between road network...

Using Time-Based Metrics to Compare Crash Risk Across Modes and Locations

Guler, S. Ilgin
Grembek, Offer
Ragland, David R.
2012

The objective of this work is to identify better metrics of exposure when comparing traffic crash risk across modes or across locations. We propose that total time travelled should be used for road user exposure to crash risk. The idea behind this is that travel time reflects the differences in speeds across different modes and hence should be used as the basic exposure metric from which crash risk based on other metrics, such as travel distance, can easily be derived. We also propose that when comparing crash risk of different modes across different locations the time-based mode share...

Weighing Integration by Block Heterogeneity to Evaluate Pedestrian Activity

Do, Minh-Tan
Grembek, Offer
Ragland, David R.
Chan, Ching-Yao
2012

Pedestrian exposure is a necessary component for a meaningful evaluation of pedestrian safety. The Space Syntax approach has a track record of accurate prediction of pedestrian activity by estimating the physical street connectivity in urban environments. However, for some environments, the performance of Space Syntax is limited and cannot be used as a reliable estimate of exposure. This paper makes use of the interdependency between: (i) street connectivity-estimated here using integration; and (ii) land-use characteristics; to propose a mechanism to adjust integration by land-use...