Road User Behavior

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.

Safety Assessment of Uncontrolled Intersections Using Both Conflict Probability and Severity

Ma, Yingying
Qin, Xiaoran
Grembek, Offer
Chen, Zhiwei
2016

This paper presents a method to assess the safety of uncontrolled intersections considering both conflict probability and severity, which are two major properties of traffic conflicts. This method provides not only the safety level of the entire intersection but also the distribution of safety within intersections. Intersections are modelled by a two-dimensional Cartesian coordinate system and the internal space of intersections is divided into cells. Firstly, vehicle movement characteristics of at uncontrolled intersections are modelled.

Modeling Secondary Accidents Identified by Traffic Shock Waves

Wang, Junhua
Liu, Boya
Lanfang, Zhang
Ragland, David R.
2015

The high potential for occurrence and the negative consequences of secondary accidents make them an issue of great concern affecting freeway safety. Using accident records from a three-year period together with California interstate freeway loop data, a dynamic method for more accurate classification based on the traffic shock wave detecting method was used to identify secondary accidents. Spatio-temporal gaps between the primary and secondary accident were proven be fit via a mixture of Weibull and normal distribution.

Recommendations to Improve Pedestrian Safety in the Town of Paradise

Dang, Tony
Alfsen, Wendy
2013

In response to the recent death of a Paradise youth who was struck on Skyway Road, the Town of Paradise invited California WALKS to facilitate a workshop providing community residents, Town staff members, and other professionals with an overview of pedestrian safety best practices, to conduct a walkability assessment of areas near the downtown core, and to lead small group discussions to develop specific recommendations for Town Council to improve the safety and walkability of Paradise.

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.

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.

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.

Combining traffic efficiency and traffic safety in countermeasure selection to improve pedestrian safety at two-way stop controlled intersections

Yang, Zhao
Zhang, Yuanyuan
Grembek, Offer
2016

Decision makers are encouraged to consider multiple objectives (such as traffic efficiency, safety, and environment) together to make decisions. Although there are methods to evaluate each objective respectively, there are few reports or research papers showing how to incorporate these objectives and put it in practice. Thus, this study aims to develop a procedure to incorporate traffic efficiency into the traffic safety countermeasure (CM) selection process.

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.

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.