Making Intersections Safer: A Toolbox of Engineering Countermeasures to Reduce Red-Light Running
An Informational Report
Chapter 1 - Introduction
One of the primary causes of crashes at signalized intersections involves a vehicle entering an intersection when the red signal is displayed. This type of collision occurs frequently. According to preliminary estimates by the Federal Highway Administration (FHWA) for 2001, the most recent year for which statistics are available, there were nearly 218,000 red-light running crashes at intersections (1). These crashes resulted in as many as 181,000 injuries and 880 fatalities, and an economic loss estimated at $14 billion per year. Clearly, red-light running, which is reported to be on the rise as with other aggressive driving behaviors such as speeding, tailgating and not stopping or even slowing at stop-controlled intersections, has become a national safety problem.
Red-light running is also a complex problem. There is no simple or single reason to explain why drivers run red-lights. There is a tendency to cite driver error-either intentional or unintentional disregard of the traffic signal. As will be presented in the report, redlight runners are more likely to be younger than 30-years old, have a record of moving violations, are driving without a valid license and/or have consumed alcohol. There are elements of driver psychology and sociology behind the violations and any driver may be susceptible to committing a violation. There is also evidence that drivers may be induced into running red lights because of improper signal design or operation. These elements make red-light running difficult to predict and a difficult problem to solve.
As with many safety problems, the solution to the redlight running problem requires a combination of countermeasures involving the three "E"s stakeholders-education, enforcement and engineering. Educational solutions start with instructing newly licensed drivers on the traffic laws and the rules regarding yellow- and red-signal displays. They continue with public information campaigns, such as television and radio public service announcements, that alert the public of the red-light running problem and its crash severity consequences.
Since every crash involving a red-light runner involves a traffic violation, it is only natural that traffic law enforcement be one of the countermeasures to consider. Enforcement includes both selective police patrols, and more recently in some jurisdictions, automatedenforcement cameras. Traditionally, police enforcement involves targeted enforcement of red-light violations at intersections with a high number of violations and/or crashes. However, this type of enforcement is labor intensive and therefore costly, and it can be hazardous, providing only short-lived effectiveness.
In some jurisdictions across the country, automatedenforcement systems, which use vehicle sensors and cameras to automatically identify a red-light runner and subsequently issue a citation, are being used to reduce these violations. Based on a recent synthesis of literature related to the safety impacts of automatedenforcement programs, these systems do reduce the incidence of red-light violations and can improve intersection safety, not only at the intersections where they are installed but at others within their influence area (2). While neither thoroughly conclusive nor consistent for all intersections, these systems tend to reduce angle crashes (those that most often result from red-light running violators) to a larger extent than the increase in rear-end crashes that may be experienced. Overall intersection safety improvement is realized because angle crashes are usually more severe than rear-end crashes, resulting in injury and/or fatality. Nonetheless, these systems have come under scrutiny and criticism for a number of reasons related to privacy and fairness. With regard to the latter, they "catch" all types of red-light runners, some who violate the signal intentionally, but others who enter on red unintentionally. This may be attributed, in part, to deficiencies related to the design and/or operation of the intersection.
Numerous reports and anecdotal evidence from around the United States and the world, suggest that there are a number of engineering features of intersections that contribute to red-light running. For example, yellowchange intervals can be set so low that they trap motorists into running red-lights. At intersections with limited sight distance to the signals, it can be difficult for a motorist to see the signals in enough time to avoid running the red-light. Since engineering deficiencies such as these can contribute to red-light running, correcting and implementing other engineering countermeasures minimize the extent of red-light running and can sometimes obviate the use of automated-enforcement systems.
OBJECTIVE OF REPORT
Often enforcement measures, whether they be selective police or automated systems, are initiated before consideration is given to addressing the problem through engineering solutions. This "toolbox" will identify what engineering features of an intersection should be considered to discourage red-light running. It addresses design and operational features that may need to be upgraded as necessary. It is intended to provide a background of the characteristics of the red-light running problem; identify how various engineering measures can be implemented to solve this problem; suggest a procedure for selecting the appropriate engineering measures; and provide guidance on when automated-enforcement systems may be appropriate.
The report is intended for several types of readers. Engineers trained in the design and operation of signalized intersections should already be cognizant of the engineering measures discussed. Still, they can benefit from being reminded of good engineering practice with the provision of a single information source focused on this topic. Law enforcement officials should become more sensitized to the various engineering features that affect red-light running and be supportive of their implementation prior to taking aggressive enforcement measures. Other officials who feel that aggressive enforcement measures, (including automated systems) should be implemented on a large scale basis will be made aware that engineering measures have the potential to reduce red-light running, which may address the resulting safety problem more adequately and equitably.
Beyond these introductory remarks, the reader will find in:
How to drive a roundabout (WSDOT)