Chapter 3: Results

Program Implementation

Based on a review of program documentation and discussions with the Project Manager and participating enforcement agencies, the Aggression Suppression Program was implemented fully and in accordance with the plan. As a result of 12 media events and other public awareness initiatives, the program generated a large volume of publicity, especially earned media coverage. The program appeared to be successful in "selling" the story to the media, especially in the initial stages of the program. Given the absence of paid media time and the fact that Milwaukee is a large and complex media market, however, it must be acknowledged that the program was not able to "saturate" the media with its message. As previously noted, only two elements of the planned publicity were not implemented as anticipated. The establishment of an aggressive driving hotline proved unfeasible because of concern for liability for the government and the cell phone companies. In addition, the use of citizen observers had limited success; only two referrals were received from the observers.

The enforcement effort was successfully implemented. Participating agencies appeared to be enthusiastically involved in the program. All enforcement strategies were implemented as planned. Apart from delays in the receipt of some of the equipment, the technological aspects of the demonstration project were implemented as planned.

Finally, the coordination of the program also went according to plan. Monthly meetings of the Advisory Committee were well attended by representatives of the participating enforcement agencies and other partners.

Enforcement Results

The primary objective of the enforcement program was to conduct increased and highly visible enforcement of aggressive driving offenses, with a particular emphasis on non-speed offenses. Detailed citation data were obtained from the Office of the Sheriff and the Milwaukee Police Department. When citations were compared for the six-month program period (April-September 1999) and the comparable six-month period in 1998, there were clear changes in the number and patterns of traffic citations issued for aggressive driving offenses. Officers in both agencies reported that aggressive driving violations became increasingly difficult to find as the program progressed.

Office of the Sheriff

Table 3.1 provides the numbers of citations issued for aggressive driving offenses by the Office of the Sheriff for April-September 1998 and 1999; these data include citations issued by the Traffic Division and by other divisions. There was a dramatic increase in the number of tickets issued for non-speed aggressive driving violations; non-speed citations increased by 55.3 percent, from 2,205 to 3,424. Increases occurred for almost all specific offenses. For example, citations issued for failure to obey a sign or signal rose from 848 in 1998 to 1,507 in 1999 (+77.7%) and citations issued for following too closely increased from 509 in 1998 to 885 in 1999 (+73.9%). Citations for speeding violations declined by 6.2 percent, from 12,647 in 1998 to 11,866 in 1999. Thus, citations for all aggressive driving offenses (including speed and non-speed violations) increased by 2.9 percent from 1998 to 1999. Citations for non-speed aggressive driving offenses represented a greater percentage of all aggressive driving citations in 1999 than in 1998 (22.4% versus 14.8%).

Table 3.1
Citations for Aggressive Driving Offenses
All Divisions of the Milwaukee County Office of the Sheriff
April – September 1998, 1999
  1998 1999 Percent Change
 1998/99
Non-Speed Violations
Deviation from Designated Lane 289 370 28.0
Failure to Obey Sign (including ramp meter violations) 848 1,507 77.7
Driving in Area not for Traffic 2 4 100.0
Failure to Signal Turn 2 17 750.0
Following Too Closely 509 885 73.9
Reckless/Aggressive Driving 51 69 35.3
Unsafe Cutting while Passing 4 3 -25.0
Unsafe Lane Deviation 500 569 13.8
Non-Speed Sub-Total 2,205 3,424 55.3
Speeding Violations
Excessive Speed 11,994 11,015 -8.2
Imprudent Speed 592 738 24.7
Too Fast for Conditions 61 113 85.2
Speed Sub-Total

12,647 11,866 -6.2
Total Aggressive Driving Offenses 14,852 15,290 2.9
Percent Non-Speed Citations 14.8 22.4

Table 3.2 provides April-September 1998 and 1999 data on citations for moving violations issued by the Traffic Division of the Office of the Sheriff. (Note that these data differ from the data presented in Table 3.1, which include citations issued by other divisions in addition to the Traffic Division.) The data provided in Table 3.2 indicate decreases in 1999, compared with 1998, for citations for speeding (-14.5%), operating while intoxicated (-0.8%), and driving with a revoked or suspended license (-10.5%). Citations for all other moving violations increased by 21.5 percent.

Table 3.2
Citations for Moving Violations
Traffic Division, Milwaukee County Office of the Sheriff
April-September 1998, 1999
  1998 1999 Percent Change
 1998/99
Speeding 11,969 10,229 -14.5
Operating while Intoxicated 360 357 -0.8
Operating after Revoked/ Suspended License 1,471 1,317 -10.5
Other Moving Violations 4,495 5,463 21.5
Non-moving Violations 1,419 1,430 0.8
Seat Belt Violations 660 792 20.0
Total 20,374 19,588 -3.9
% Other Moving Violations 22.1 27.8

Throughout the program, the Traffic Division, Office of the Sheriff, tracked the citations designated as "aggressive" driving violations. Table 3.3 provides the numbers of these citations issued during April-September 1999 by the grant-funded squads, the straight-time patrols representing the County’s match, and the other regular patrols. The grant squads issued 2,102 tickets during the six-month program; the match squads issued 718 citations.

Table 3.3
Citations for Aggressive Driving Offenses
Traffic Division, Milwaukee County Office of the Sheriff
Grant Squads, County Match Squads, Regular Patrols
April-September 1999
  Grant
Squads
County
Match
Squads
Regular
Patrol
Total
Failure to Obey Sign 591 181 732 1,504
Unsafe Lane Deviation 107 27 311 445
Speeding (20 MPH over) 806 292 2,555 3,653
Following Too Closely 217 58 558 833
Too Fast for Conditions 2 0 76 78
Deviation from Designated Lane 48 18 128 194
Driving in Area Not for Traffic 4 2 32 38
Failure to Stop for Sign 4 0 12 16
Reckless Driving 5 1 47 53
Operating after Revocation/Suspension 13 17 0 30
Operating while Intoxicated 2 0 0 2
Miscellaneous 303 122 60 485
Total 2,102 718 4,511 7,331

City of Milwaukee

The number of citations issued by the Milwaukee Police Department for non-speed aggressive driving offenses increased from 9,528 during April-September 1998 to 12,378 during April-September 1999, an increase of 29.9 percent (Table 3.4). For example, citations for disregarding an official sign or signal increased by 45.6 percent. Citations issued for speed violations increased by 2.7 percent. Thus, total citations for both speed and non-speed aggressive driving violations increased by 13.7 percent from 1998 to 1999. Citations for most other types of moving violations, unrelated to aggressive driving, declined during this period.

As a percentage of citations for all moving violations, aggressive driving citations increased from 39.2 percent in 1998 to 44.0 percent in 1999, while non-speed aggressive driving citations increased from 15.9 percent to 20.4 percent.

Table 3.4
Citations for Moving Violations
City of Milwaukee Police Department
April-September 1998, 1999
  1998 1999 Percent Change
 1998/99
Deviating in Traffic 845 830 -1.8
Disregarding Official Sign/Signal 4,899 7,135 45.6
Failure to Yield Right-of-way 1,419 1,471 3.7
Other Moving Violations 2,215 2,739 23.7
Reckless Driving 150 203 35.3
Total Non-Speed Aggressive 9,528 12,378 29.9
Speeding 13,994 14,376 2.7
Total Aggressive Citations 23,522 26,754 13.7
Operating while Intoxicated 1,702 1,396 -18.0
Auto License Law 8,480 9,319 9.9
Driver License Law 19,313 16,610 -14.0
Seat Belt Violations 4,832 4,848 .3
Failure to Turn in Plates 2,215 1,832 -17.3
Total Moving Violations 60,064 60,759 1.2
Percent Aggressive 39.2 44.0
Percent Non-Speed Aggressive 15.9 20.4

Table 3.5 provides counts of citations issued for aggressive driving offenses by the City’s grant-funded patrols and the non-grant patrols. The grant patrols issued 4,405 citations during the six-month grant period. More than half these citations were issued for disobeying a stop sign or signal. A review of the citations by the grant-funded officers indicated that the large majority of tickets were issued along the targeted corridors and/or at the targeted intersections.

Table 3.5
Aggressive Driving Offenses
City of Milwaukee Police Department
Grant Patrols and Non-grant Patrols
April-September 1999
  Grant
Patrols*
Non-Grant
Patrols
Disobeying Stop Sign/Signal 2,216 4,919
Speeding/Racing 1,780 12,174
Illegal Turn 101 390
Failure to Yield Right-of-Way 98 1,373
Lane Deviation 56 886
Failure to Signal 30 23
Illegal Use of Horn 15 8
Following Too Closely 10 260
Illegal Passing 10 65
Driving Wrong Side 4 117
Reckless Driving 4 199
Failure to Stop at Crossing 3 3
Illegal Backing 1 91
Other 77 69
Total 4,405 20,577

*Note: Grant Patrol Citations do not include 2,397 citations for traffic violations that were not judged to be aggressive driving.

Suburban City Agencies

Three suburban city law enforcement agencies undertook State-funded aggressive driving programs in conjunction with the efforts of the City of Milwaukee Police Department and the Office of the Sheriff. Although no historical data were available for comparison, these agencies reported the numbers of citations for aggressive driving offenses that were issued by the grant-funded patrols during their project period, May-September 1999. It should be noted that seat belt and child safety seat enforcement was a focus of these grant, as well as aggressive driving violations.

Most of the special enforcement undertaken by the City of Wauwatosa Police Department was conducted on the feeder streets leading to the Milwaukee County freeway systems. The department issued a total of 244 citations and 123 warnings for aggressive driving offenses and seat belt/child restraint offenses.

The City of West Allis Police Department reported that it made one enforcement contact every 22 minutes. The agency’s special enforcement occurred primarily on Friday nights and during rush hours, when drivers were most likely to speed and engage in other aggressive behaviors. From May to September, 1,217 citations and warnings were issued.

The City of Glendale Police Department issued 293 citations for aggressive driving offenses and seat belt/child restraint violations.

Agencies’ Assessment of Enforcement Efforts

According to the Project Manager and the key officers involved in the Aggression Suppression Program from the City of Milwaukee Police Department and the Office of the Sheriff, the program was successful in securing buy-in from the general traffic patrols. The City’s motorcycle traffic officers and officers in the Traffic Division, Office of the Sheriff, demonstrated enthusiastic support for the program. Factors believed to contribute to this success were the roll call videotape, which provided a good introduction to the program, and the rotating focus among the enforcement of different violations, which helped sustain officers’ interest in the program. The agencies also found the educational flyer on aggressive driving to be useful. It served as a reminder for officers to concentrate on aggressive driving violations and was given to violators issued tickets. In addition, agencies were positive about the use of the magnetic vehicle "Aggressive Diving Patrols" signs. When the signs were first introduced, some were blown off the vehicles when officers on the freeways forgot to remove the signs before driving off at high speeds.

Enforcement agencies reported that the use of electronic speed display boards helped raise awareness of the increased enforcement, especially when the boards were used in conjunction with officers using either laser or radar speed equipment. It also was noted that to achieve maximum effectiveness, the board should be placed at a new location after a few days. The LTI 20-20 Ultra-Lyte laser speed equipment was well received by motorcycle officers and other officers working on the grant. The units proved to be light and easy to use. Because they are battery operated, cumbersome cords are eliminated. Officers reported that the lighter units resulted in less fatigue, and thus, increased use.

Officers were less enthusiastic about the LTI laser distance-between-cars (DBC) feature of the laser guns. The feature was designed to calculate the distance between two vehicles traveling in the same direction, one in front of the other, and to aid the officer in enforcement of citations for tailgating. The Aggression Suppression Program had not intended to use the DBC equipment as a basis for writing citations; rather, the program provided an opportunity to conduct a field test to assess the feasibility of using the equipment for enforcement. Program staff met with prosecutors and judges to explain the equipment, but the DBC evidence was not used as part of officers’ testimony in court. Officers reported that the DBC equipment had considerable value in convincing motorists that they had, in fact, been tailgating. It also was believed that publicity about the equipment had a general deterrent effect, although delays in receiving the equipment meant that the announcement of its use occurred later than planned.

However, despite its obvious public relations value, officers found the DBC equipment to be an impractical way to measure tailgating. Officers found it difficult to accomplish the needed quick and accurate aiming of the laser in heavy traffic. In addition, the entire procedure was complex. To achieve accurate measurement of the distance between two vehicles, the officer must first aim at the front of the first vehicle and press the trigger of the unit. Then the officer must quickly aim at the front of the second vehicle and press the trigger to receive the measure of distance, expressed in either feet or seconds. Because the reported distance is measured between the fronts of the vehicles, the officers must mentally estimate and subtract the length of the front vehicle from the reported distance in order to obtain the length of the gap between the two vehicles. In addition to the need for officers to develop skill in using the DBC equipment, its use required a team of two officers – one officer to operate the equipment and a second officer to apprehend the violator.

The three suburban law enforcement agencies reported that the State-funded program in aggressive driving was well received by their agencies. Two of these agencies noted that many of their roadways were under construction during the program period. Some special enforcement was targeted to these areas since the congestion and delays created by construction were believed to increase the occurrence of aggressive driving.

Although there were concerns prior to the program’s inception that prosecutors and judges would have difficulty with the increase in non-speed citations, no such problems were reported. In addition, although it had been anticipated that a large number of criminal arrests would take place during enforcement of aggressive driving offenses, this was not the case.

Driver Surveys

Self-administered surveys were distributed to drivers obtaining or renewing their driver license at the five offices of the Wisconsin Department of Motor Vehicles (DMV) located within Milwaukee County. Since all drivers in Wisconsin must obtain or renew their license in person, this provided a feasible, low-cost method to survey a representative sample of Milwaukee drivers.

Method

Three waves of surveys were conducted: one in March 1999, prior to the implementation of the program; one in July 1999, at the height of the program; and one in October 1999, soon after program activities had ended. DMV employees distributed the one-page survey to all persons either obtaining or renewing their license, and drivers were asked to deposit the completed survey in a "Completed Survey" box. Completed surveys totaled 1,417 in March, 1,538 in July, and 1,261 in October.

In order to limit the survey instrument to a single page, two versions of the instrument were prepared. Both versions gathered basic demographic information, including gender, age, race or ethnicity, and zip code. All survey respondents also were asked how many miles they expected to drive in the next year. Both versions of the instrument also included questions on the following topics:

The respondents also were queried about the nine specific aggressive driver actions addressed by the program and the associated publicity campaigns, including. The survey items on the following topics were divided between the two versions of the instrument:

Responses were compared between the pre-program and mid-program surveys, and between the pre-program and post-program surveys. Statistical significance was based on the chi-square test, with p < 0.01 defined as significant. Responses also were examined by respondent characteristics, but no consistent patterns were identified.

Results

For all three waves of the survey combined, 52.0 percent of the respondents were male. About one-third were less than 25 years old, one-third were 26-39 years old, and one-third were 40 years or older. More than half the respondents were non-Hispanic white (56.5%), 31.1 percent were non-Hispanic black, 6.7 percent were Hispanic, and the remaining respondents belonged to other ethnic or racial groups.

About half the drivers surveyed in the pre-program survey (48.3%) believed that Milwaukee drivers were ruder, when compared to a year ago; about half (47.9%) believed that drivers were about the same, and only a few drivers (3.7%) believed they were much more or more courteous. These results did not change significantly across the three waves of the survey.

The perceived strictness of general traffic enforcement was at a high level in the baseline survey. A large majority of respondents (70.5%) reported that the County and City police departments enforce traffic laws either somewhat strictly or very strictly. This percentage declined to 63.3 percent in the mid-program survey (p < 0.01). The percentage then rose in the post-program survey to 67.9 percent, which did not differ significantly from the pre-program percentage.

Although significant improvements did not occur in the perceived strictness of general law enforcement, drivers became more likely to believe that they would be ticketed for certain aggressive driving violations. The percentage of drivers who believed that they would always/nearly always receive a ticket for running a red light increased from 42.4 percent in the baseline survey to 49.1 percent in the mid-program survey (p < 0.01). Similarly, the percentage that believed they would always or nearly always receive a ticket for running a stop sign increased from 36.8 percent in the baseline survey to 45.4 percent in the mid-program survey (p < 0.01). Changes between the pre-program and post-program periods were not significant.

About 56 percent of the respondents in all three survey waves indicated that they had recently seen, read, or heard something about police enforcement of traffic laws in Milwaukee. With regard to the source of this information, in each survey about one in three of these respondents mentioned television, one in four mentioned newspapers, and one in six mentioned radio. Less than five percent mentioned posters, brochures, or checkpoints.

There was a significant increase between the baseline and mid-program surveys in the percentage of respondents who reported that they had recently seen, read, or heard anything about the campaign Rude Attitude Patrol (14.1% to 19.8%, p < 0.01), and about the State’s "Let It Ride" campaign (12.6% to 18.2%, p < 0.01). There were significant increases between the pre-program and post-program surveys in the percentage of respondents who had recently seen, read, or heard anything about the Space Patrol campaign (8.5% to 13.3%, p < 0.01), the Courtesy Patrol campaign (16.0% to 25.0%, p < 0.01), and the Rude Attitude Patrol campaign (14.1% to 25.9%, p < 0.01). Although there were increases in the awareness of other campaign themes over the program period, these increases were not statistically significant. In each survey, driver awareness was highest for the "Buckle Up America" campaign, a national campaign to increase seatbelt use; about two-thirds of drivers in each survey had recently seen, read, or heard something about this campaign. It should be noted that the survey did not query drivers about their awareness of the overall campaign slogan, Aggression Suppression, since the choice of a slogan had not been finalized when the baseline survey was conduced.

A set of questions focused on the extent to which drivers believed nine specific aggressive driving behaviors cause problems. As shown in Table 3.6, in the baseline survey, drivers believed that cutting off other drivers (47.0%) or running a red light (43.3%) was most likely to always/nearly always cause a problem.

Table 3.6
Perceptions of the Problem Caused by 
Aggressive Driving Behaviors
Survey of Milwaukee Drivers
March 1999
  Always/Nearly Always a Problem
Cutting Off Other Drivers 47.0%
Running Red Light 43.3%
Weaving In and Out of Traffic 41.5%
Driving through Stop Sign 41.3%
Failure to Signal Turn/Lane Change 40.1%
Tailgating 40.0%
Exceeding Speed > 10 MPH 33.5%
Passing on Right 29.0%
Honking, Flashing Lights, Gesturing 27.6%

More drivers in the mid-program survey than in the baseline survey believed that running a red light (43.3% versus 51.2%, p < 0.01) or driving through a stop sign (41.3% versus 48.1%, p < 0.01) was always/nearly always a problem. Fewer drivers in the mid-program survey believed that weaving in and out of traffic (41.5% versus 34.2%, p < 0.01) or exceeding the speed limit by at least 10 MPH (33.5% versus 27.3%, p < 0.01) was always/nearly always a problem. There were no significant differences between the baseline and post-program responses for any of these reported behaviors.

A final set of questions focused on how often, if ever, drivers had engaged in each of these specific driving behaviors in the last 30 days. In the baseline survey, the following percentages of drivers reported that they had engaged in these behaviors on at least one occasion in the past 30 days: traveling at least 10 MPH over the speed limit (67.4%); failing to signal a turn or lane change (47.0%); passing on the right (32.4%); weaving in and out of traffic (28.9%); tailgating (28.8%); honking, flashing lights, gesturing (27.5%); cutting off other drivers (22.8%); driving through a stop sign (13.0%); and running a red light (11.9%). The reported frequency of these behaviors did not differ statistically across the three waves of the survey.

Observations of Driver Behavior

Video cameras were used to record traffic at selected sites during a baseline period prior to the program, midway through the program, and after the program had ended. The videotapes were analyzed to derive counts of selected aggressive driving actions. Observations were conducted at selected signalized intersections and along a stretch of interstate highway.

Red Light-Running

Observations were conducted at 20 signalized intersections to determine whether the extent of red light-running declined as a result of the program. Ten of the intersections were targeted by enforcement and public awareness efforts (i.e., target intersections), and 10 were matched comparison intersections.

The baseline observations were conducted from March 23 to April 8, the mid-program observations were conducted from July 15 to August 2, and the post-program observations were conducted from October 19 to December 9. Observations were conducted during rush hours Monday-Friday, 6:45 a.m. – 8:45 a.m. and 3:30 p.m. – 5:30 p.m., with the cameras focused on the direction of heaviest traffic density. Half the matched pairs of target/comparison intersections were observed in the morning, and half were observed in the afternoon/evening. Thus, for each observational wave (baseline, mid-program, post-program) a total of 40 hours of videotapes was generated, including 10 hours of morning observations and 10 hours of afternoon/evening observations for the target intersections, and 10 hours of morning and 10 hours of afternoon/evening observations for the comparison intersections.

One person coded all 120 hours of videotapes. The tapes were "blindly" coded; that is, the coder did not know whether the intersection was a target or comparison site. The order in which the tapes were coded ensured that baseline, mid-program, and post-program tapes were evenly dispersed throughout the coding period. The following coding procedures were established:

Due to extreme sun glare and the position of the camera, some tapes at some intersections could not be coded. Table 3.7 reports the results for the seven pairs of target/comparison intersections for which data were available for all three observational periods. With "no opportunity" light cycles excluded, the percentage of vehicles coded as stopped differed little between target and comparison sites or across waves; the percentage stopped ranged from 59.2 percent to 65.9 percent. However, the percent egregious red light-running declined at the target intersections from the pre-program period to the mid-program period (6.5% versus 4.9%), and the percent egregious red light-running increased at the comparison intersections (2.9% to 12.7%). The percentage then increased from the mid-program period to the post-program period for the target intersections and was essentially unchanged at the comparison sites.

Table 3.7
Milwaukee Aggression Suppression Program
Observed Red Light-Running Behavior
Target and Comparison Intersections
Pre-program, Mid-program, Post-program
  Percent
Egregious
Percent
Marginal
Percent
Stopped
Percent
Total
Pre-Program
Target Sites 6.5 31.2 62.3 100.0 (n=220)
Comparison Sites 2.9 31.2 65.9 100.0 (n=200)
Mid-Program
Target Sites 4.9 34.0 61.1 100.0 (n=324)
Comparison Sites 12.7 24.7 62.6 100.0 (n=173)
Post-Program
Target Sites 10.3 27.0 62.7 100.0 (n=251)
Comparison Sites 12.0 28.8 59.2 100.0 (n=202)

Paired comparison tests were conducted to test the statistical significance of the changes in the percent of egregious red light-running between the pre-program, mid-program, and post-program periods. The first test examined these differences between the pre-program and mid-program periods, using paired data for the eight experimental intersections and the eight control intersections for which pre-program and mid-program data were available. For the experimental intersections, the percent egregious red-light running declined, on average, by –1.90 percentage points. For the control intersections, the percent egregious red-light running increased, on average, by +8.60 percentage points. The difference in these results was statistically significant (t = -3.466, p < 0.01, df = 7). A similar test was conducted for the differences between the pre-program and post-program periods, based on the seven pairs of intersections for which pre-program and post-program data were available. The experimental intersections experienced, on average, an increase of +3.73 percent points in egregious red light-running, and the control intersections experienced an increase of +9.06 percentage points, on average. The difference was not significant.

Highway Aggressive Driving

A field test was conducted to assess the feasibility of identifying and coding highway aggressive driving behaviors, using videotaped observation data. Traffic was videotaped along a stretch of the U.S.-45/I-894 freeway, using one of the traffic monitoring cameras mounted at intervals along the Milwaukee freeway system and connected into the Wisconsin DOT Traffic Operations Center. Traffic moving in three lanes in one direction was videotaped on several days prior to the program, midway during the program, and after the program had ended. From the large number of videotapes produced, a balanced sample of tapes was selected for analysis; the sample included videotapes of morning and afternoon rush-hour traffic. In all, 18 hours of videotapes were selected for coding. It should be noted that although the target videotaped intersections were selected because they had been targeted by special enforcement efforts, the videotaped highway segment was not targeted for special enforcement, apart from the overall increased highway enforcement of aggressive driving offenses.

After a review of several hours of videotapes, it was determined that the coding procedures would focus on three types of aggressive driving actions, including spacing violations (tailgating and cutting into), weaving, and excessive speed. Each aggressive event also was given one of three severity codes: 1) egregious, i.e., clearly dangerous; 2) clear but not egregious; or 3) probable. A single person coded all 18 hours of videotapes, with the order of coding fixed to balance the number of tapes from each wave coded in the first, second, and final thirds of the coding activity.

The identification and coding of aggressive behaviors by drivers proved to be problematic in several respects. The camera’s field of view permitted only a small segment of roadway to be filmed, and only about one-quarter mile could be effectively analyzed and coded. In general, only about 10 to 15 seconds of travel by a vehicle could be analyzed. Together with the heavy traffic congestion, this meant that a relatively small number of aggressive incidents could be observed. In addition, given the limited view afforded by the single, stationary camera, the heavy traffic congestion, and the short roadway segment, it was sometimes difficult to determine whether behaviors were "aggressive." For example, some types of aggressive driving involve a series of driving behaviors, which is difficult to detect in a few seconds of tape on a short stretch of roadway. Varying traffic volume, speed, and density also were of concern. As a result, the analysis of the sample of videotapes did not yield useful information.

Crash Data

The City of Milwaukee’s Planning and Development Unit, Transportation Section, Infrastructure Services Division, Department of Public Works, provided baseline and program police-reported crash data. A special crash report, generated for the evaluation, provided the numbers of total, fatal, personal injury, and property-damage crashes during each of the months March-September for 1998 and 1999. Property-damage crashes were classified as "Property Damage +" or "Property Damage –" depending on whether or not the amount of property damage exceeded a reporting threshold. Detailed crash reports were generated for the entire City of Milwaukee, for each of the eight corridors targeted by the Milwaukee Police Department for intensified enforcement of aggressive driving offenses and for each of eight matched comparison corridors. To the extent possible, crashes were included if at least one involved vehicle was driving along the corridor road prior to the crash.

The analyses provided below were drawn from reports that provided monthly counts, by severity, of overall crashes, multiple-vehicle crashes, and crashes occurring at intersections. The number of crashes occurring during the program period, April-September 1999, was compared to the number of crashes occurring during a baseline period, April-September 1998. Baseline/program changes in the number of citywide crashes, compared to the expected totals, were tested with the chi-square statistic. Changes in crashes occurring on the target and comparison corridors are also described. Since the target corridors were selected, in part, because they had a history of high-crash incidence, differences in crash patterns on the target and comparison corridors were not submitted to statistical tests.

A final set of analyses looked at crashes involving at least one driver aggressive action as a contributing crash factor. Aggressive driving actions included exceeding the speed limit, speed too fast for conditions, failing to yield right-of-way, following too closely, making an improper turn, disregarding a traffic control, and improper overtaking.

As shown in Table 3.8, the overall number of crashes that occurred in the City of Milwaukee fell from 8,632 during the six-month period in 1998 to 8,217 in 1999, a decline of 4.8 percent (p < 0.01). Crashes involving an injury or fatality declined by 6.6 percent, and the number of property-damage crashes decreased as well.

Total crashes for the eight target corridors combined declined by 12.3 percent from 1998 to 1999. Personal injury and fatality crashes occurring on the target corridors declined by 11.3 percent, and property damage crashes also declined. The number of total crashes occurring along the comparison corridors declined by 2.2 percent, and personal injury/fatality crashes declined by 1.2 percent.

Table 3.8
Police-reported Crashes
Target and Comparison Roadway Corridors and Citywide
City of Milwaukee
April-September 1998, 1999
  1998 1999 Percent Change
 1998/99
Target Corridors
Personal Injury or Fatality 372 330 -11.3
Property Damage + 358 336 -6.1
Property Damage - 172 125 -27.3
Total 902 791 -12.3
Comparison Corridors
Personal Injury or Fatality 245 242 -1.2
Property Damage + 269 266 -1.1
Property Damage - 134 126 -6.0
Total 648 634 -2.2
Citywide
Personal Injury or Fatality 2,915 2,723 -6.6
Property Damage + 3,887 3,831 -1.4
Property Damage - 1,830 1,663 -9.1
Total 8,632 8,217 -4.8

Table 3.9 provides information on crashes involving more than one vehicle. Citywide, multiple-vehicle crashes declined overall and within each category of severity; the 4.6 percent decline for all crashes represented a significant change (p < 0.01). Total multiple-vehicle crashes occurring along the target corridors declined by 14.5 percent from 1998 to 1999. A smaller decline of 3.4 percent occurred for multiple-vehicle crashes along the comparison corridors. There were declines in the number of crashes in all severity categories for the target corridors; for the comparison corridors, smaller percentage declines occurred for personal injury/fatality crashes and non-reportable property damage crashes, while reportable property damage crashes increased slightly.

Table 3.9
Multiple-Vehicle Crashes
Target and Comparison Roadway Corridors and Citywide
City of Milwaukee
April-September 1998, 1999
  1998 1999 Percent Change
 1998/99
Target Corridors
Personal Injury or Fatality 321 280 -12.8
Property Damage + 338 304 -10.1
Property Damage - 166 121 -27.1
Total 825 705 -14.5
Comparison Corridors
Personal Injury or Fatality 219 206 -5.9
Property Damage + 246 248 0.8
Property Damage - 126 117 -7.1
Total 591 571 -3.4
Citywide
Personal Injury or Fatality 2,203 2,092 -5.0
Property Damage + 3,465 3,403 -1.8
Property Damage - 1,664 1,498 -10.0
Total 7,332 6,993 -4.6

Traffic crashes at intersections were of particular interest, since much of the special enforcement targeted red light-running, running a stop sign, and blocking an intersection. As shown in Table 3.10, a significant decline of 7.8 percent was observed for crashes at intersections citywide (p < 0.01). The number of total crashes occurring at intersections along the target corridors decreased by 16.3. Crashes at intersections decreased by 6.3 percent along the comparison corridors.

Table 3.10
Crashes at Intersections
Target and Comparison Roadway Corridors and Citywide
City of Milwaukee
April-September 1998, 1999
  1998 1999 Percent Change
 1998/99
Target Corridors
Personal Injury or Fatality 254 215 -15.4
Property Damage + 230 200 -13.0
Property Damage - 61 41 -32.8
Total 545 456 -16.3
Comparison Corridors
Personal Injury or Fatality 170 161 -5.3
Property Damage + 165 152 -7.9
Property Damage - 45 43 -4.4
Total 380 356 -6.3
Citywide
Personal Injury or Fatality 1,761 1,623 -7.8
Property Damage + 1,888 1,775 -6.0
Property Damage - 590 509 -13.7
Total 4,239 3,902 -7.8

A final set of analyses focused on the police-reported possible contributing circumstance of a crash (Table 3.11). Crashes were selected if the investigating law enforcement officer indicated a driver factor considered "aggressive." The number of crash-involved drivers with at least one aggressive contributing factor declined by 18.6 percent for the target corridors and by 8.1 percent for the comparison corridors.

Table 3.11
Crash-Involved Drivers with at Least One Aggressive Factor
as Possible Crash Contributing Circumstance
Target and Comparison Roadway Corridors and Citywide
City of Milwaukee
April-September 1998, 1999
  1998 1999 Percent Change
 1998/99
Target Corridors
Exceeding Speed Limit 18 13 -27.8
Speed Too Fast for Conditions 33 20 -39.4
Fail to Yield Right-of-Way 229 185 -19.2
Following Too Closely 80 63 -21.2
Making an Improper Turn 32 32 0.0
Disregarding Traffic Comparison 101 93 -7.9
Improper Overtaking 18 10 -44.4
Total 511 416 -18.6
Comparison Corridors
Exceeding Speed Limit 12 12 0.0
Speed Too Fast for Conditions 18 17 -5.6
Fail to Yield Right-of-Way 132 122 -7.6
Following Too Closely 71 54 -23.9
Making an Improper Turn 22 21 -4.5
Disregarding Traffic Comparison 73 75 2.7
Improper Overtaking 6 6 0.0
Total 334 307 -8.1