We have all witnessed or experienced vehicles that run a red light, whether it was the result of intentional or unintentional driving behavior. The Federal Highway Administration (FHWA) has identified the underlying causes of red-light violations: 44% are due to inattentiveness; 33% are due to intentional actions; 15% are due to driver confusion; and 6% are due to vehicle problems or environmental conditions. The societal economic loss is estimated at $14 billion a year, resulting from the 168,000 injuries and 850 fatalities nationwide (2004 National Highway Traffic Safety Administration statistics) caused by red-light violation crashes. The statistics indicate that the primary cause of the red-light violations is poor decisions made by the driver.
Red-light violations are arguably the most dangerous situation that motorists face on a regular basis. Statistics in the state of Michigan indicate that 36% of all severe crashes at signalized intersections are a result of red-light violations, although these crashes represent only 17% of all crashes at signalized intersections. The disproportionate nature of the crash severity makes reducing red-light violations a worthy goal for improving traffic safety.
Grounding the punishment
The measures commonly used to improve traffic safety fall into the categories of education, engineering and enforcement. Education usually consists of driver education and traffic safety classes for drivers that have a history of repeated traffic citations. Media reports about red-light running also could be considered education.
Enforcement comprises conventional enforcement and automated enforcement, which utilizes a camera at the intersection to identify red-light violators so that a citation can be issued. Some states have legislation that allows for automated enforcement, but many do not. For states that do have such legislation, automated enforcement is often viewed as the single solution to the problem and generates a new revenue stream by increasing the number of citations. Lawmakers and the public may feel as if the problem has been sufficiently mitigated by automated enforcement.
In reality, automated enforcement is solely intended to punish poor driver behavior, rather than improve driver behavior by providing the cues needed to make better driving decisions. If a groundswell of public pressure in favor of red-light violation enforcement does not occur, it is typically because of the fear of governmental surveillance (Big Brother privacy concerns) or political, policy and institutional issues.
Engineering safety countermeasures are often overlooked, although many options have been identified in the publications developed by the Institute of Transportation Engineers (ITE). In addition, well-engineered traffic-signal timing plans will minimize the number of vehicles that might otherwise enter the intersection during the yellow or red light.
Looking for cues
Red-light violations are a growing problem that is difficult to counteract. The severity of the problem is typically based on public perception when a high-profile crash occurs. Lawmakers have created tough red-light violation legislation or made provisions for automated red-light running enforcement in direct response to a high-profile crash.
In contrast, the actual red-light violation rate at a signalized intersection is rarely measured or considered a benchmark for making decisions about countermeasures.
Motorists use many external cues when making driving decisions. The cues that influence driver behavior are critical to providing a safe driving environment, particularly at signalized intersections. These cues include traffic-control elements, such as pavement markings, signs and traffic-signal displays, the general layout of the intersection and other elements.
Traffic-control elements in various forms can serve as engineering-based countermeasures to provide better cues to the driver, thereby improving safety.
The position of traffic-signal displays within the intersection is one of the most important cues. A recent FHWA driver behavior study was conducted at signalized intersections in Michigan before and after the configuration of the traffic-signal displays were modified. In the before condition, the traffic-signal heads were located in a diagonal configuration across the intersection. In the after condition, the traffic-signal heads were located at the far side of the intersection in a box-span arrangement. The net effect is that the location of the traffic-signal displays was shifted from the near side to the far side of the intersection.
It pays to be early
The research hypothesis of this study was that a typical driver is generally uncomfortable with viewing a red indication as he or she passes through an intersection, since the driver may have witnessed his or her own red-light violation. The traffic-signal head location change will likely put more drivers in that uncomfortable position, potentially reducing the number of vehicles entering the intersection during the four seconds surrounding the beginning of the red interval. These four seconds include the last second of the yellow interval and the first three seconds of the red interval. Late-yellow entry is defined as the last second of the yellow light, just prior to changing to the red light. If the rate of the red-light violations and late-yellow entry events decreased during the four seconds surrounding the beginning of the red interval, then the research hypothesis would be confirmed.
To test the hypothesis, one approach was studied at three intersections. The intersection approaches were similar in their lane configuration and approach speed. The traffic-signal operational parameters (including clearance intervals) were kept the same between the before and after time periods. The differences included the location of the traffic-signal displays. Approximately three weeks of data was collected during both time periods.
The average rate reduction was 54% among the three sites for the combination of late-yellow entry and red-light violation rate during the four seconds surrounding the beginning of the red interval. The number of red-light violations represented about 10% of the entering vehicles, and late-yellow entry events represented about 90% of the entering vehicles.
The red-light violation rate (first three seconds) and late-yellow entry rate (last one second) declined substantially at each site, with the exception of the red-light violation rate at the Southfield site. Based on the limited duration and scope of the study, the combination event results are considered the most meaningful result, rather than the red-light violation rate or late-yellow entry rate individually.
The reduction in red-light violations and late-yellow entry appeared to vary based on how close the existing traffic-signal displays were located with respect to entering the intersection. The most substantial rate reduction occurred where the traffic-signal displays were 40 ft or less from the approach stop bar prior to moving the signal displays to the far side of the intersection.
Driver behavior appears to be influenced by the position of the traffic-signal heads, which is an engineering countermeasure. When the opportunity arises to install or modernize a traffic-signal installation, the traffic-signal design should accommodate far-side traffic-signal displays to maximize the safety potential of the intersection.
Further research is needed to fully confirm that driver behavior has been permanently influenced by the far-side traffic-signal displays.
Scoping the area
A challenging aspect of red-light running research is measuring the problem in the field. Currently, the most common tool used is crash statistics over a period of time (typically three years). While helpful, this method is unable to measure changes in driver behavior without waiting for a long period of time to pass. The monitoring equipment used for automated enforcement is expensive, and a portion of the red-light violation fines are typically used to pay for the equipment, but the monitoring equipment is not intended to be used as a measuring tool for engineering purposes.
The monitoring tool used as part of the FHWA driver behavior study measured the red-light violations and late-yellow entry events accurately and at a low cost. An AutoScope Solo II video detector, an off-the-shelf product commonly used for vehicle detection at signalized intersections, was wired directly into the traffic-signal cabinet. The traffic data was collected by a laptop computer housed in the traffic-signal cabinet, downloaded and processed to isolate the red-light violation information.
The video detector collected the vehicle speed, intersection entry time, traffic volume and “depth of red,” which is the number of seconds after the signal turns red that a vehicle enters the intersection. A few weeks of red-light monitoring data is usually sufficient to determine if the intersection has a red-light running problem or if the current driver behavior appears to be within a typical range.
The information about red-light violations throughout the day also can be used to provide law enforcement with the time periods when violations occur most frequently, maximizing the benefit of conventional enforcement resources. Automated enforcement should be considered if engineering countermeasures fail to provide a lasting red-light violation reduction.
Further refinement of this monitoring tool by URS Corp. allows for examination of red-light violations in a cost-effective and timely manner. It is based on the principle that better engineering can reduce the number of red-light violations by improving driver behavior rather than assuming that the exclusive solution is to counteract poor driver behavior through automated enforcement.
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