Chapter 4: Discussion

The present results should be considered within the context of the state of knowledge about aggressive driving at the time the project was undertaken. As with any newly emergent area, there is much that remains to be discovered. Although there is a sense that we "know it when we see it," there is no set of agreed-upon measures to quantify aggressive driving. There are hypotheses about its causes and the circumstances that may trigger a specific incident, but these hypotheses have not been tested or made operational. We have better, but still incomplete, evidence about the types of drivers who are more likely to engage in aggressive acts. Better knowledge about the nature and causes of aggressive driving, and about at-risk drivers and driving situations, will aid especially in developing effective public awareness strategies that persuade drivers not to engage in this behavior.

It is clear, however, that there also is widespread belief among highway safety professionals and the public that aggressive driving is a growing problem that must be addressed. In response, states and communities have begun to develop programs and/or draft legislation. Ideal countermeasures should be based on an in-depth understanding of the scope and nature of the problem and the at-risk populations.

In initiating the Aggressive Driving Demonstration Projects, NHTSA’s primary objective is to test the effectiveness of applying a well-tested general program model – a Selective Traffic Enforcement Program (STEP) – to aggressive driving. A STEP model employs publicized and intensified traffic enforcement at specific locations. The selection of the locations and the types of traffic offenses is based on an above-average number of crashes with contributing factors that are the result of particular types of offenses. The STEP model has proven effective in addressing different areas of highway safety, for example, DUI, speeding, occupant restraints.

There are other important objectives for these projects as well. One is to test alternative publicity and enforcement strategies, including the use of innovative technologies to identify and document aggressive driving behaviors. Another objective is to test the willingness, and the ability, of law enforcement officers to enforce a wide range of traffic offenses in addition to speeding. Finally, NHTSA hopes to expand the state of knowledge about how to define and measure different types of aggressive driving behaviors.

It is within this context that Milwaukee’s Aggression Suppression Program was launched. The test site, the City and County of Milwaukee, has a history of strong traffic enforcement and successful community highway safety programs. A strong coalition to implement the program was in place. Historical crash and citation data enabled the program’s planners to identify problem locations and ensured that the effects could be evaluated. The activities were well documented, and all evidence indicates the program was fully implemented as planned, with strong support from all partners. A thorough evaluation was conducted, with evidence gathered to establish the "causal chain" linking program activities and outputs with changes in drivers’ attitudes and behaviors, and ultimately with reductions in crashes.

How did the program fare in terms of the established objectives? The program was clearly successful in broadening enforcement efforts to target a wide range of aggressive driving offenses in addition to speeding violations. There were large percentage increases in the numbers of citations issued by the City and County agencies for non-speed violations. The program also succeeded in targeting enforcement to certain areas of the City and certain times.

Officers demonstrated enthusiastic support for the program. For the most part, the innovative equipment aided in enforcing aggressive driving offenses. The speed display boards, in-vehicle video cameras, and LTI laser speed detection devices were well received by officers. Enforcement agencies were able to identify other aspects of the enforcement program that worked especially well. These included the roll call videotape, which provided a good introduction to the program, and rotating the enforcement focus among different violations, which helped sustain officers’ interest in the program. Other factors noted as particularly successful were the educational flyer on aggressive driving given to violators, the use of magnetic vehicle signs, and the intersection patrols. Officers were less enthusiastic about the LTI distance-between-cars technology; the process to obtain accurate measurements of distances was complex.

In terms of the publicity component, considerable earned coverage was generated, especially at the outset. Twelve media events were held. Many publicity materials were distributed. Paid advertising was not considered for this demonstration because law enforcement agencies wishing to replicate the successes in Milwaukee would likely not have funds for paid media. However, it is doubtful that the campaign was able to saturate the media market, which may be needed to have a demonstrable effect on the general driving public’s attitudes and behaviors.

A much more intensive an/or much more focused publicity effort may be needed to produce greater changes in the public’s attitudes and behaviors, especially in a community like Milwaukee with a long history of highway safety programs and strong enforcement. The use of enforcement/publicity sub-themes appears to have been successful in sustaining the interest of the media and participating enforcement agencies. Other apparently successful strategies were staging novel media events (for example, patrol ride-alongs) and highlighting innovative enforcement technologies and strategies. However, the multiple messages, each presented only briefly, may not have had the reinforcing effect of a sustained message necessary to change overall public attitudes. The more direct, straightforward sub-themes (for example, Rude Attitude Patrol) appeared to have more effect than the more indirect, subtle sub-themes (for example, Kindergarten Patrol or Basket Patrol).

With regard to changes in motorists’ driving behaviors, videotapes of traffic at target and comparison intersections proved to be a feasible method for measuring the extent of red light-running. The analysis of before/during/after data indicated a decline in red light-running at the targeted intersections between the pre-program and mid-program periods. Although suggestive of program effect, this evidence must be viewed cautiously; enforcement was intensively targeted to these intersections, but heightened enforcement also occurred citywide.

The use of videotapes to document other types of aggressive driving on a major highway was less successful. (The highway segment videotaped was not targeted for special enforcement.) The identification and coding of aggressive behaviors on the highway proved to be problematic in several respects, due to the camera’s limited field of view, heavy traffic congestion, and the inability to account for varying traffic volume, speed, and density. The process of coding these videotapes also highlighted the difficulty of using observational data to judge whether a given incident occurring in a very limited span of time and space is "aggressive." Many types of aggressive driving involve a series of behaviors.

The results with regard to motorists’ self-reported behaviors and attitudes were mixed. Based on surveys of the general driving population, changes in motorists’ perceptions of the strictness of enforcement did not occur, but the pre-program survey indicated that there was already a high level of perceived strictness of enforcement in Milwaukee. Most of the self-report measures of attitudes and behaviors remained relatively flat across the three waves of the survey. However, drivers in the mid-program survey were significantly more likely than drivers in the pre-program survey to believe that they would be ticketed for running a red light or for running a stop sign. Drivers in the mid-program survey also were more likely to believe that running a red light or driving through a stop sign was always/nearly always a problem. The level of awareness of the specific campaign themes was low in all three waves of the survey. However, statistically significant increases in the level of awareness occurred for the themes of Rude Attitude Patrol, Courtesy Patrol, Space Patrol, and the State’s concurrent "Let It Ride" campaign. Given the timing of the baseline survey, information was not available on the level of awareness of the overall campaign theme of Aggression Suppression.

Analyses of before/after crash data suggested that the program was associated with declines in crashes citywide. Overall levels of crashes declined significantly in the City, and the reductions were greatest on the roadway corridors targeted by special enforcement.

In sum, the Aggression Suppression Program demonstrated the effects of targeted enforcement. More citations were issued for aggressive driving types of violations (that is, not just speed tickets were issued); motorist behavior changed at targeted intersections; and crash reduction was demonstrated citywide, with greater reductions on corridors with targeted enforcement. Future programs of this type would be enhanced if they could generate more visible and more focused media attention.