Motorized Vehicle Safety

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. Secondly, conflict probability of each cell within...

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. A logistic regression model was developed to investigate major factors...

Identification of Freeway Secondary Accidents with Traffic Shock Wave Detected by Loop Detectors

Wang, Junhua
Xie, Wenjing
Liu, Boya
Fang, Shou'en
Ragland, David R.
2016

Secondary traffic accidents are generally recorded without being specifically noted as such in the accident database, leading to difficulty in the study of such accidents. Previous research generally classified secondary incidents by predefining fixed spatio-temporal boundaries—a method that can be very subjective. Using 10,762 accident records gathered from 2012 upstream loop detector data on a California interstate freeway, this paper proposes a dynamic method for more convincing and accurate classification based on traffic shock waves detected by the loop detectors. This method...

Utilizing the Eigenvectors of Freeway Loop Data Spatiotemporal Schematic for Real Time Crash Prediction

Fang, Shou'en
Xie, Wenjing
Wang, Junhua
Ragland, David R.
2016

The concept of crash precursor identification is gaining more practicality due to the recent advancements in Advanced Transportation Management and Information Systems. Investigating the shortcomings of the existing models, this paper proposes a new method to model the real time crash likelihood based on loop data through schematic eigenvectors. Firstly, traffic volume, occupancy and density spatiotemporal schematics in certain duration before an accident occurrence were constructed to describe the traffic flow status. Secondly, eigenvectors and eigenvalues of the spatiotemporal schematics...

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. The current...

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...

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...

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...

A 3D Computer Simulation Test of the Leibowitz Hypothesis

Barton, Joseph E.
Cohn, Theodore E.
2007

Do large objects appear to approach more slowly than smaller objects traveling at the same speed? If so then this might help explain the inordinately high accident rates involving large vehicles such as buses and trains. To test this, this study constructed an experiment using a 3D visual simulator in which different sized textured spheres approached at different speeds. We found that observers consistently judged the smaller sphere to be the faster, even in cases where the larger sphere was traveling at up to twice the speed of the smaller. Analysis of these results suggests that the...

Child Restraint Use: Workbook and Guide for Evaluating Community-based Programs

Ragland, David R.
Geyer, Judy A.
Cooper, Jill F.
2003

The leading cause of injury and death for children in California is motor vehicle crashes. To prevent these needless tragedies, the California Office of Traffic Safety (OTS), through the Business, Transportation and Housing Agency, funds child passenger safety programs throughout the state. This workbook is designed to be used by these local programs to 1) evaluate the impact of their activities on child restraint use, 2) evaluate results to improve or modify the programs as needed, and 3) meet contractual evaluation requirements. Program evaluations can be difficult for local programs due...