This report presents the results of a study conducted for the National Highway Traffic Safety Administration (NHTSA) to assess the effects of two enforcement programs that were implemented to reduce the incidence of aggressive driving. The programs were conducted by the Marion County Traffic Safety Partnership (a consortium of agencies in the vicinity of Indianapolis, Indiana), and The Tucson, Arizona, Police Department. The programs each received grants of $200,000 from NHTSA to support the special enforcement and public information and education (PI&E) components. Program managers were required, as conditions of the grant, to 1) focus their enforcement efforts on key aggressive driving infractions in carefully-selected zones within their communities; 2) develop and implement PI&E campaigns to publicize the special enforcement efforts; and, 3) provide the data and other information necessary to prepare this evaluation. The programs shared additional features, but program managers were encouraged to consider innovative approaches to both special enforcement and publicity.
Both the Marion County Traffic Safety Partnership and the Tucson Police Department developed vigorous PI&E programs. The Marion County program featured professionally-produced television and radio PI&E messages and an emphasis on paid and donated advertising. The centerpiece of the Tucson PI&E program was an aggressive driving hotline, supported by billboards and printed materials, that generated public interest and considerable free publicity. The special enforcement efforts of both programs involved both marked and unmarked vehicles and a focus on drivers who exhibited any of the moving violations that frequently are associated with aggressive driving, including speeding, failure to obey traffic controls/devices, failure to yield, improper or unsafe lane changes, and following too closely.
Samples of vehicle speed, collected unobtrusively in the special enforcement zones, and crash incidence served as the primary measure of program effect. Average speeds declined slightly in Marion County and to a greater degree in Tucson. The total number of crashes in the Marion County special enforcement zones increased by 32 percent, compared to the same six-month period one year earlier, and the number of those crashes with primary collision factors (PCFs) associated with aggressive driving increased by 41 percent. That is, the total number of crashes increased, but the crashes with aggressive driving PCFs increased at a greater rate. The change in proportion of crashes with the target PCFs provides a better overall measure than crash frequency because it eliminates the effects of changes in traffic volume and other factors that might have contributed to the overall increase in crash incidence. In this regard, the Marion County zones experienced a six percent increase in the proportion of all crashes with aggressive driving PCFs, despite the extensive publicity and special enforcement efforts of the Marion County Traffic Safety Partnership. The number of crashes in Tucson’s special enforcement zones increased by ten percent, but the number of crashes with aggressive driving PCFs increased by less than one percent. More important, the proportion of all crashes with target PCFs decreased by eight percent. That is, crash incidence increased overall in Tucson’s zones, but the proportion of those crashes with aggressive driving PCFs declined.
Study results suggest that limited resources might be better spent on officer labor than on publicity, and that focusing enforcement responsibility on a small team assigned full-time to the special enforcement patrols might be more effective than sharing the responsibility among a large number of officers as occasional overtime duty. The study also shows that crashes caused by aggressive driving can be deterred by a combination of PI&E and enforcement.