Which vehicles are likely to keep going when the light turns from yellow to red just as they come to an intersection? The study described below found that older, smaller cars more often run red lights, and the drivers are generally younger than the people who will stop for the light. They are also more likely not to be wearing safety belts and to have a record of previous traffic violations.

The Insurance Institute for Highway Safety supported a field investigation to learn what characteristics distinguished drivers who ran a red light at an urban intersection from those who did not. Richard A. Retting and Allan F. Williams wrote up the results of the study, which were published October 1994 in a paper entitled Characteristics of Red Light Violators: Results of a Field Investigation.

Background

Retting and Williams cited a 1994 study that found 56 percent of nonfreeway crashes in four urban areas of the United States happened at intersections. The same research concluded that 22 percent of the crashes studied happened because a driver had run a traffic control; this was the largest single cause of these intersection crashes. Studies in England and Australia yielded similar conclusions.

Attempting to learn more about drivers who ran red lights, a 1991 study compared those at fault in crashes resulting from running a red light with those not at fault. The red-light violators were more likely to be under 35 years of age and male. A 1980 study of drivers in Baltimore found that those who ran red lights had substantially lower [seat]belt use rates.

Study Design

For the study described in this report, researchers compared a group of drivers who ran red lights with a group who had the opportunity to do so but did not. They collected data in Arlington County, Virginia at the intersection of an eight-lane east/west principal arterial roadway (six through lanes plus left-turn lanes) and a four-lane north/south collector street. Specifically, the data were for vehicles and drivers going east on the arterial; the speed limit was 45 miles per hour. Virginia law requires drivers to stop when confronted by a steady yellow light if it is not reasonably safe to continue. Retting and Williams described the length of the signal clearance interval (yellow and all-red phases) as consistent with the recommended practice of the Institute of Transportation Engineers.

Observers and electronic equipment collected data. The observers watched from a parked van. When a driver ran the red light, observers noted several things: (1) type of vehicle, (2) vehicle make and color, (3) gender of the driver, (4) driver s estimated age, and (5) if the driver wore a shoulder belt. When no red-light runners came through during a light cycle, they collected information on the first vehicle that had the opportunity to run the light but stopped. Drivers had to be between 250 and 375 feet from the light when it changed, or researchers considered them too close or too far away to classify as having an opportunity to run the light. Observers used a hand-held camera to photograph vehicles that stopped for lights, and a computerized red-light camera system photographed vehicles that ran lights. The red-light camera took a picture of the back of each vehicle that entered the intersection one-half second or more after the light turned red.

During eight weeks of February, March, and April 1994, researchers collected 234 hours of data. They worked from 9:00 a.m. to 5:00 p.m.--daylight hours--and only when the pavement was dry. Traffic signals were functioning correctly, and all roadway markings were clearly visible. Data did not include turning vehicles.

Using license plate numbers, researchers obtained motor vehicle records from Virginia, Maryland, and the District of Columbia. Of the 1,373 vehicles included in the study, motor vehicle records matched the vehicles described in 1,102 cases. If records for these 1,102 vehicles showed the registered owner s gender and age (within 10 years) matched the gender and age of the driver seen by observers, researchers assumed the driver was the owner. The description of the observed driver matched information on the owner in 547 cases. For these cases, researchers requested the owners driving records. In addition, vehicle identification numbers (VINs) provided information on vehicle body styles and wheelbase dimensions.

Results

Of the 1,373 vehicles recorded by observers, 462 violated a red light and 911 complied with a red light when they had the opportunity to run it--that is about two red-light runners each hour. Although researchers found no significant differences between violators who ran the light immediately after it turned red and those who entered the intersection long after the light had changed, they did classify the violating group by the degree of violation. They found that 48 percent entered 0.5 to 0.9 seconds after red onset, 34 percent entered 1.0 to 1.4 seconds after red onset, 11 percent entered 1.5 to 1.9 seconds after red onset, and 7 percent entered after the light had been red for at least 2.0 seconds.

While 75 percent of the vehicles observed had Virginia license plates, Virginia drivers represented 79 percent of people who complied with the red light and only 67 percent of red-light violators. In contrast, Maryland and Washington, D.C. drivers showed larger percentages of people who violated the law than who complied with it--19 percent violators compared with 13 percent compliers for Maryland and 9 percent compared with 7 percent for Washington, D.C.

Violators drove older cars than compliers. Thirteen percent of violator-driven passenger vehicles were manufactured after 1991, while 20 percent of law-abiding motorists drove vehicles manufactured after 1991. Researchers found passenger cars, cargo vans, pickups, and utility vehicles equally likely to run the red light. However, red-light runners were more likely to drive smaller cars--10 percent of compliers had cars with a wheelbase of more than 109 inches compared with 6 percent of violators.

Male drivers made up 71 percent of both complying drivers and violating drivers. Overall, violators were younger, with 26 percent of violators being under 30 and only 14 percent of compliers under 30. Violators were more likely to be driving without a shoulder harness--67 percent of red-light runners wore harnesses compared with 71 percent of compliers.

The study showed that motorists who ran red lights were often the same people who had received speeding tickets. The authors stated, Violators were over three times more likely than compliers to have multiple speeding convictions on their driver records. Virginia maintains 60-month historical records of driving violations and awards drivers negative and positive points according to their number of (or lack of) violations--the higher the point total, the better the driving record. Driving records for the motorists in this study showed that violators had a lower average point balance than compliers, and were twice as likely as compliers to have very low point balances. On the other hand, prior crash figures of Virginia drivers were about the same for the two groups--13 percent of violators and compliers had a crash on their records.

Discussion

The authors concluded, [R]ed light runners are a higher risk group that merits enforcement resources not only because of the violation itself and its danger, but because of their higher risk characteristics in general. One reason for undertaking this study was concern over the high incidence of intersection crashes and the contribution running red lights makes to this problem. Although researchers found no correlation between involvement in previous crashes and running the red light, they pointed out, Department of motor vehicle files, such as those used in this study, are known to provide an incomplete record of crash experience.

According to the study, two red-light violations occurred each hour at one urban intersection. This suggests running red lights may be a significant problem across the United States. The authors described two countermeasures: improving enforcement and modifying the timing of traffic signals or the design of intersections.

Lack of funding for police resources often makes enforcement more difficult. In addition, pursuing violating vehicles through urban traffic can be dangerous. Retting and Williams mentioned that automated detection devices, such as red- light cameras, have successfully reduced violations and intersection crashes in other countries.