Traffic Tech #292: Aggressive Driving Enforcement In Two Demonstration Communities

The words aggressive driving emerged during the 1990s as a label for a category of dangerous on-the-road behaviors.... following too closely, driving at excessive speeds, weaving through traffic, and running stop lights and signs, among other acts. The National Highway Traffic Safety Administration (NHTSA) defines aggressive driving as the operation of a motor vehicle in a manner that endangers or is likely to endanger persons or property. An important distinction is that aggressive driving is a traffic violation, while road rage is a criminal offense.

Several factors can contribute to a single example of aggressive driving and it is important to understand that not all instances of behaviors categorized as aggressive driving are volitional. For example, errors in judging turning headway can result in right of way violations or crashes, and driver inattention can result in failure to obey traffic signals or signs. Driving in excess of a speed limit does not always endanger persons or property, nor does it necessarily involve an aggressive intent. Some factors, excluding human error, that are believed to contribute to conscious decisions to drive aggressively include: disregard for the law and for others, traffic delays, running late, anonymity, and habitual or clinical behavior (e.g., an individual predisposed to angry confrontation across a diverse spectrum of situations).

The Marion County Traffic Safety Partnership in Indianapolis, Indiana, and the Tucson Arizona Police Department received grants to support special enforcement and public information and education to reduce aggressive driving in specially designated enforcement zones.

Marion County Traffic Safety Partnership Rub Out Aggressive Driving (R.O.A.D.) Team Program

Six law enforcement agencies participated by devoting almost 1,400 officer hours to special patrols along three special enforcement zones over a six month period. Squads of five officers targeted the morning and evening commuting periods about every third day, concentrating on drivers exhibiting two or more aggressive driving violations. They bought advertising on television and radio and issued press releases periodically during the program, among other activities.

Tucson Police Department "We've Got Your Number Program"

Aggressive driving is a separate offense in Arizona. Two officers were assigned full time responsibility to patrol the four special enforcement zones in unmarked police vehicles with motorcycle backup nearby nearly every day of the six month program. Two additional officers in unmarked vehicles added another day every week to the enforcement effort.

An Aggressive Driver Hot Line was setup to receive calls and complaints from citizens who reported the license plate number of the offending vehicles. The lieutenant in charge responded by sending letters to both the caller and the registered owner of the offending vehicle, warning that further reports could result in enforcement action. The program was promoted on pizza boxtop flyers, bumper stickers, ride-alongs by news reporters, radio and television coverage, and displays at special events.

Local Prosecutors

Program managers in both programs worked with local prosecutors during the planning and implementation phases. In Marion County, violators who had been designated as aggressive drivers were ineligible for the Safe Driver diversion program (for those who have had no prior traffic convictions). In Tucson, collaboration between law enforcement and the courts resulted in a standardized plea agreement that ensured uniform prosecution of aggressive drivers.

Speed Measurements

Speed measurements before the program began showed that Marion County drivers averaged +5 to +11 mph over the posted speed limit on the target roadways. Measurements taken during the enforcement period did not differ much, ranging from 0 to +2 mph difference from the baseline measurements. Drivers in Tucson averaged -3 to +7 mph from the posted speed limit on the targeted roads before the program, and this did not change much during the enforcement period, averaging from 1 to 3 mph difference from the baseline measurement.

Crashes

Analyzing crashes along specific roadway zones can be problematic because of the small numbers of crashes that occur in any given month, yielding large fluctuations. Crashes that occurred in the special enforcement zones and comparison zones during the six months of the program were compared to the same six month period one year earlier. Total crashes increased in both areas by about one-third in Marion County and by 20 percent in the enforcement zones and by 7 percent in the comparison zones in Tucson. Although crashes increased overall in Tucson's zones, the proportion of those crashes with aggressive driving primary collision factors (PCFs) declined.

The report discusses factors that may have contributed to the speeding and crash behavior along the special enforcement zones in both programs. Traffic volume may have increased as roadway maintenance diverted more vehicles into the enforcement zones. Not all negative driving behaviors result in a crash, and it may be that the test zones were simply too small, the number of crashes too few, or the measures too insensitive to detect any differences due to enhanced enforcement using these measures.