Aggressive

Driving

Enforcement

Evaluations of Two 

Demonstration Programs

March 2004

1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No.

DOT HS 809 707

4. Title and Subtitle 5. Report Date

 Aggressive Driving Enforcement: Evaluation of Two Demonstration Programs March 2004

7. Authors 6. Performing Organization Code

n/a

Jack Stuster, PhD, CPE 8. Performing Organization Report No.

n/a

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

Anacapa Sciences, Inc.

P.O. Box 519 11. Contract No.

Santa Barbara, CA 93102 DTNH22-98-D-05079

12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered

National Highway Traffic Safety Administration Final Report

400 Seventh Street, SW

Washington, D.C. 20590

15. Supplemental Notes 14. Sponsoring Agency Code

Patricia Ellison-Potter, PhD, was the Contracting Officer’s Technical

Representative (COTR) for this project.

16. Abstract

This report presents the results of a study conducted for the National Highway Traffic Safety

Administration (NHTSA) to assess the effects of two 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.

Samples of vehicle speed, collected unobtrusivelyin the special enforcement zones, and crash incidence served

as the primary measures of program effect. Average speeds slightly in Marion County and at a greater rate 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; 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 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. 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.

17. Key Words 18. Distribution Statement

Traffic Safety, Aggressive Driving, Road Rage

Traffic Enforcement

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified

Form DOT 1700.7

AGGRESSIVE DRIVING ENFORCEMENT:

EVALUATIONS OF TWO DEMONSTRATION PROGRAMS

EXECUTIVE SUMMARY

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 carefullyselected 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.
TABLE OF CONTENTS

Page

INTRODUCTION .......................................................................................................................... 1

Background....................................................................................................................... 1

Contributing Factors To Aggressive Driving.............................................................. 4

THE PROGRAMS ......................................................................................................................... 9

PROGRAM RESULTS ................................................................................................................... 17

Speed Samples.................................................................................................................. 17

Crash Data......................................................................................................................... 20

Program Awareness........................................................................................................ 25

IMPLICATIONS ............................................................................................................................ 27

Explanation........................................................................................................................ 30

Why Aren’t the Programs More Effective? ................................................................. 31

Recommendations ........................................................................................................... 32

ACKNOWLEDGMENTS................................................................................................................ 33

REFERENCES .............................................................................................................................. 35

APPENDIX A: CONTRIBUTING FACTORS TO AGGRESSIVE DRIVING ............................................ 37

APPENDIX B: DATA TABLES....................................................................................................... 41
TABLE

Table Page

1 CHANGES IN POPULATION, FATALITY RATE, AND THE NUMBERS OF DRIVERS, VEHICLES,

AND MILES TRAVELED IN THE U.S. BETWEEN 1991 AND THE YEAR 2000 ..................... 3

2 SUMMARY OF ENFORCEMENT EFFORT BY THE TWO AGGRESSIVE DRIVING PROGRAMS.. 15

3 MARION COUNTY UNOBTRUSIVE SPEED SAMPLES: COMPARISON OF AVERAGE BASELINE

SAMPLES TO AVERAGE OF SAMPLES DURING THE PROGRAM PERIOD ............................ 18

4 TUCSON UNOBTRUSIVE SPEED SAMPLES: COMPARISON OF AVERAGE BASELINE

SAMPLES TO AVERAGE OF SAMPLES DURING THE PROGRAM PERIOD ............................ 19

5 SUMMARY OF ALL CRASH MEASURES DURING THE PROGRAM PERIOD AND THE

SAME SIX-MONTH PERIOD ONE YEAR EARLIER: MARION COUNTY SPECIAL ENFORCEMENT

AND COMPARISON ZONES............................................................................................. 21

6 SUMMARY OF ALL CRASH MEASURES DURING THE PROGRAM PERIOD AND THE

SAME SIX-MONTH PERIOD ONE YEAR EARLIER: TUCSON SPECIAL ENFORCEMENT

AND COMPARISON ZONES.............................................................................................. 23

7 RESPONSES TO THE MARION COUNTY PUBLIC AWARENESS SURVEY QUESTION #1 ....... 25

8 RESPONSES TO THE MARION COUNTY PUBLIC AWARENESS SURVEY QUESTION #2 ....... 26

9 SUMMARY OF KEY CRASH MEASURES DURING THE MARION COUNTY AND TUCSON

PROGRAM PERIODS AND THE SAME SIX-MONTH PERIODS ONE YEAR EARLIER ............. 28

10 CHANGES IN TRAFFIC VOLUMES IN THE MARION COUNTY AND TUCSON

SPECIAL ENFORCEMENT ZONES: YEAR 2000 TO 2001.................................................... 29

FIGURES

Figure Page

1 Fatality Rates Per 100 Million Miles Traveled in the U.S. ..................................... 3

2 Salient Factors That Contribute To the Incidence of Aggressive Driving ......... 4

3 Comparison of Program Costs................................................................................ 15

4 Marion County Speed Sample Results.................................................................... 18

5 Tucson Speed Sample Results................................................................................... 19

6 Crashes in the Marion County Special Enforcement Zones................................ 20

7 Crashes in the Tucson Special Enforcement Zones............................................... 22
– 1 –

INTRODUCTION

This report presents the results of a study conducted for the National Highway

Traffic Safety Administration (NHTSA) to assess the effects of two programs that were

implemented to reduce the incidence of aggressive driving. This brief introduction

discusses the reasons for conducting the study. Subsequent sections of the report are

devoted to descriptions of the countermeasure programs, the results of the programs,

and the implications of study results.

BACKGROUND

The words, “aggressive driving,” emerged during the 1990s as a label for a

category of dangerous on-the-road behaviors. The category comprises following too

closely, driving at excessive speeds, weaving through traffic, and running stop lights

and signs, among other acts. Aggressive driving occasionally escalates to gesturing in

anger or yelling at another motorist, confrontation, physical assault, and even murder;

“Road Rage” is the label that emerged to describe the angry and violent behaviors at

the extreme of the aggressive driving continuum. 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, aside from the yelling and gesticulating, is a criminal

offense.

People have reported the occasional on-the-road behavior that we now describe

as aggressive driving since the advent of motorized transport, and quite possibly, since

the beginning of vehicular travel. Anyone who has spent more than a few hours in an

automobile has experienced the rudeness of other drivers. Until the final decade of the

Twentieth Century, most motorists were comforted by knowing that aggressive

driving behavior was infrequent and atypical, and that extreme, confrontational acts

were quite rare. However, beginning in the 1990s, an unrelenting series of news reports

captured the public’s attention and elevated to a national problem what previously had

been considered to be, simply, rude and occasionally bizarre human behavior.1

The shocking reports of road rage incidents appeared to many observers to

coincide with a noticeable increase in aggressive driving, in general, and a sharp decline

in civility and respect for other motorists and traffic laws. The AAA Foundation for

Traffic Safety studied more than 10,000 reported cases of road rage and found a 51

percent increase in serious incidents between 1990 and 1996 (Mizell, 1997). A national

survey found that 60 percent of motorists believe that unsafe driving by others is a

major personal threat to them and their families; 75 percent of the respondents consider

it to be “very important” to do something about unsafe driving (NHTSA, 1999).

 

1 For example, following separate disputes in traffic: a Massachusetts bookkeeper murders another

motorist with a single shot from a crossbow; a soccer mom runs another woman off the road, and to her

death, in Mississippi; two Virginia men crash into oncoming traffic, killing three drivers, as the final

act of an angry, on-the-road duel; a Maryland lawyer punches a pregnant woman after a minor fenderbender; in California, a famous actor uses a golf club to repeatedly smash the window and roof of a

vehicle that cut him off in traffic; a driving instructor in North Carolina tells his student to chase a

vehicle that cut them off and subsequently punches the offending driver; a high-school athlete is shot

to death over a stop sign right-of-way dispute in New Mexico, and the incident is quickly followed by

two more local fatalities attributed to “road rage.”
– 2 –

It is reasonable to question the claims of dramatic increases in aggressive driving

and road rage. For example, Mizell’s estimate of a 51 percent increase in extreme cases

was based on news reports, but the amount of reporting on a topic in a particular year

is influenced by journalists’ interest in an issue, not necessarily the actual incidence of

the phenomenon in question. Even accepting Mizell’s estimate of 10,000 cases of road

rage during the first six years of the 1990s, the incidence is really quite low compared to

the numbers of injuries and fatalities that occur on our nation’s roads and highways.

During the same six year period studied by Mizell, more than 22.7 million people were

injured in motor vehicle crashes in the U.S., and more than 290,000 people were killed

(FARS, 2000). That is, the number of cases of road rage was only .04 percent of the total

number of people injured or killed in traffic (i.e., four one-hundredths of a percent), or

one case of road rage for every 2,300 injuries and fatalities. The relative size of the road

rage problem is further revealed by comparisons to subsets of traffic crash data. For

example, 33,521 pedestrians and 4,782 bicyclists were killed, and 531,000 pedestrians and

385,000 bicyclists were injured during the six year period in which Mizell counted 10,000

cases of road rage with various outcomes (FARS, 2000).

The crash data suggest that road rage is a relatively small traffic safety problem,

despite the volume of news accounts and the general salience of the issue. It is important to consider the issues objectively because programmatic and enforcement efforts

designed to reduce the incidence of road rage might detract attention and divert

resources from other, objectively more serious traffic safety problems. Although cases

of road rage are relatively rare, the incidence of aggressive driving is much more frequent and a measurable contributing factor to traffic crashes.

The perceived increase in aggressive driving is largely explained by demographic

changes. In particular, the population of the United States increased by nearly 100

million people between 1960 and the year 2000, and by 35 percent since 1970, the year

that NHTSA was created with the mission of improving traffic safety. Traffic safety has

improved significantly, with fatality rates declining from 5.5 per million miles traveled

during the mid-1960s to 1.5 fatalities per million miles traveled in the year 2000. Figure 1

illustrates the change in fatality rate since 1966 (FARS, 2000).

The numbers presented in Table 1 show that the final decade of the Twentieth

Century was a period of rapid population growth, with even greater increases in

individual mobility and improvements in the ultimate measure of traffic safety. The

table shows that the population of the U.S. increased by 22 million people between 1991

and the year 2000, an increase of nine percent. However, the number of licensed drivers

increased by 21 million during the same period (an increase of 13 percent), and there

were 30 million additional vehicles (an increase of 16 percent) and nearly 600 billion

additional miles traveled in the year 2000 than in 1991 (an increase of 27 percent). That

is, the number of miles traveled in a year increased at a rate that is three times the rate

of population growth. The table also shows that despite the 27 percent increase in miles

traveled between 1991 and the year 2000, a driver was 21 percent less likely to die in a

motor vehicle crash at the end of the decade than at the beginning. In other words, it is

safer to drive on our nations roads and highways now than ever before, despite the

increases in population, miles traveled, and aggressive driving. How is this possible?
– 3 –

0

1

2

3

4

5

6

1966

1967

1968

196919701971197219731974197519761977197819791980

1981

19821983198419851986

19871988

19891990199119921993

19941995

Fatality Rate per Million Vehicle Miles Travelled

19961997199819992000

Figure 1. Fatality rates per 100 million miles traveled in the U.S.

TABLE 1

CHANGES IN POPULATION, FATALITY RATE, AND THE NUMBERS OF DRIVERS, VEHICLES, AND

MILES TRAVELED IN THE UNITED STATES, BETWEEN 1991 AND THE YEAR 2000

United States Licensed Registered Vehicle Miles

Population Drivers Vehicles Traveled Fatalities Per

Year (millions) (millions) (millions) (billions) 100 Million Miles

1991 252.1 169.0 186.4 2,172 1.9

2000 274.6 190.6 217.0 2,750 1.5

Change +9% +13% +16% +27% -21%

Sources: FARS 2000, US Census

Improved safety features of vehicles and highways, and a general aging of the

population, have contributed incrementally to the steady decline in the traffic fatality

rate. However, since 1980, the greatest contributions to the improved conditions have

come from law enforcement efforts, in particular, a focus on detecting and removing

impaired drivers from the road and the development of general deterrence and

effective public information and education (PI&E) programs. Largely in response to the

enforcement and programmatic efforts, the proportion of all crashes in which alcohol

was involved declined by 25 percent during the 1990s; there were 3,200 fewer alcoholrelated traffic fatalities in the year 2000 than in 1991, even though the numbers of

drivers, vehicles, and miles traveled all increased substantially. Law enforcement and

traffic safety experts believe that some of the methods that helped reduce the incidence

of alcohol-involved crashes also might be useful for reducing the number of crashes

caused by aggressive driving.
– 4 –

CONTRIBUTING FACTORS TO AGGRESSIVE DRIVING

A definitive explanation for aggressive driving is beyond the scope of the current

study. However, a brief discussion of contributing factors might be useful to understanding study results. Experts have suggested many reasons for the apparent increases

in aggressive driving and road rage. Sociologists point to the fragmentation of society

and the disintegration of shared values and sense of community as the cause of these

and other acts of incivility. Many psychologists blame the intoxicating combination of

power and anonymity provided by motor vehicles. Traffic engineers tend to ignore the

human component, recognizing that crashes can occur when a vehicle that is traveling

at the design speed of a roadway encounters a slower moving vehicle. The engineering

solution is to encourage all drivers to travel at uniformly fast speeds to avoid the potentially dangerous encounters, but this approach disregards different perceptions of

conditions and differences in motorists’ destinations, intentions, and capabilities.

Many law enforcement officers have learned from their operations-level experiences with dangerous drivers that several factors can contribute to a single example of

aggressive driving. Further, it is important to understand that not all instances of the

behaviors that are categorized as aggressive driving are volitional. For example, errors

in judging turning headway can result in right of way violations, and driver inattention

can result in failures to obey traffic signals and signs. Also, driving in excess of a speed

limit does not always endanger persons or property, nor does it necessarily involve an

aggressive intent. That is, an unknown portion of all such driving acts is caused by

human error, rather than conscious decisions to take risks and drive aggressively.

Figure 2 illustrates the most salient factors, excluding human error, that are believed to

contribute to the apparent increase in the incidence of aggressive driving behavior. The

factors are summarized in the following paragraphs.

Speeding

Weaving Through Traffic

Running Stop Signs/Lights

Failing to Yield Right of Way 

Tailgating

Running Late

Traffic Delays

Anonymity

Disregard

for

Others

Disregard

for the

Law

Habitual

or Clinical

Behavior

Figure 2. Salient factors that contribute to the incidence aggressive driving.
– 5 –

TRAFFIC DELAYS

Traffic congestion is one of the most frequently mentioned contributing factors

to aggressive driving. On-the-road delays, whether caused by highway maintenance, a

collision, or high traffic volumes, are frustrating for all drivers, but intolerably so for

some. Drivers with low tolerances for traffic delays might respond by following too

closely, changing lanes frequently, or becoming angry at anyone who impedes their

progress. A 1998 survey found that 33 percent of drivers reported that they become

impatient while waiting at stoplights and for parking spaces; 25 percent reported

impatience while waiting for passengers to enter their vehicle; and, 22 percent said that

they feel anger when a multi-lane highway narrows (Ferguson, 1998).

The survey results concerning driver impatience and anger are particularly

revealing when considered in the context provided by Table 1, and one additional

statistic. That is, while the number of miles traveled increased by 27 percent during the

1990s, the number of miles of roadway in the United States increased by only one

percent. Together, these measures confirm and quantify most drivers’ subjective

perceptions; traffic congestion has, indeed, increased.

RUNNING LATE

Some people drive aggressively because they have too much to do and are

“running late” for work, school, their next meeting, lesson, soccer game, or other

appointment. There does, indeed, appear to be more to do with each passing year. It is

reported that the average mother now spends more than an hour making five trips and

driving 29 miles during a typical day. Many of the stops are to drop off or pick up children or elderly parents who cannot drive themselves (STPP, 2002). The endless series of

errands and obligations of modern life weighs more heavily and/or more frequently

on some individuals than on others, and can contribute to a pattern of aggressive driving. The effects of busy schedules on driving were evident when several police departments in the Washington, DC, area conducted a special enforcement program that

targeted aggressive drivers. Officers issued approximately 60,000 citations during a 28

day period in 1997 for offenses ranging from following too closely to passing on the

right. The most frequent excuse offered by the violators was, “I’m late” (Ferguson,

1998).

ANONYMITY

Driving involves a unique combination of public and private behavior. A motor

vehicle insulates the driver from the world while, at the same time, traveling through it.

Shielded from the hostile outside environment by tinted windows and a micro-climate

that defies the seasons, a driver can develop a sense of anonymity and detachment, as if

an observer of the surroundings, rather than a participant. The anonymity provided by

this insulation can erode the inhibitions to antisocial behavior that normally shape

interpersonal relations. That is, some people feel less constrained in their behavior

when they cannot be seen by others and/or when it is unlikely that they will ever again

see the witnesses to their behavior. When emboldened by the seemingly invincible

power of a motor vehicle, a driver’s feeling of anonymity can result in extreme rudeness and even transform an otherwise nice person into a dangerous, raging individual.2

 

2 Perhaps the elevated perspective from the driver’s seat of a sport utility vehicle (SUV) contributes to

feelings of both anonymity and invincibility, a hypothesis worthy of testing. Further, many sport

utility vehicles seem to be designed more for war than civilian transportation. In this regard, the term

“urban assault vehicle,” frequently used to describe SUVs, is strangely appropriate, particularly in the

context of the familiar metaphors, “fighting traffic” and “it is a jungle out there.”
– 6 –

Ellison et al. (1995) tested the hypothesis that vehicle-induced anonymity

contributes to aggressive behavior, wisely limiting the dependent variables to measures

of relatively harmless horn honking. Convertibles and jeep-like vehicles were delayed

at controlled intersections by an automobile, operated by a confederate of the

experimenters, that failed to proceed when the light changed to green. The confederate

recorded whether the top on the delayed convertible (immediately behind the

confederate’s vehicle) was up (the anonymous condition) or down (the exposed or

identifiable condition). Several additional variables were recorded, including the gender

and age of the driver, the number of passengers, and the type of vehicle. The

confederate also recorded the time interval between the change to the green light and

the first sounding of the convertible’s horn, the number of honks, and the duration of

the honking. As predicted, the experimenters found that drivers in the anonymous

condition (convertible tops up) honked significantly sooner, more frequently, and for

longer durations than the drivers in the exposed condition (tops down).

Gulledge (1996) modified the research design by using a convertible as the

impeding vehicle at intersections, with the convertible’s top up for half of the trials and

the top down for the other half. Only the time interval between the light change and

the first honk by the delayed driver (any passenger vehicle located immediately behind

the experimenter’s convertible) was recorded. Analysis of the data found significantly

longer intervals between the light change and the first use of the horn when the top on

the delaying convertible was down, exposing the experimenter and driver to view. The

results of this study suggest that greater visibility of the intended target also inhibits

horn honking, and that mutual anonymity is a factor in at least some aggressive driving

behaviors.

DISREGARD FOR OTHERS AND DISREGARD FOR THE LAW

Human behavior is clearly shaped by the external forces collectively known as

Culture. The external source of the influence and degree to which norms can change are

illustrated by the music, clothing, or salutation that seemed so “stylish” or appropriate

in 1970, and so odd or inappropriate now. All forms of human behavior, including

driving style, are similarly influenced by external forces that define what is appropriate

and what is not, and the definitions change over time.

Feature films and television programming can be extremely influential in

defining current style and appropriate or desirable behavior. The extent of media

influence on popular culture and behavior is not fully understood. In particular, it is

unknown if depictions of car chases influence motorists to drive aggressively by

gradually altering individual conceptions of acceptability, or more immediately, by

providing vivid images of aggressive behavior for motorists to model. Children

predictably exhibit the aggressive behavior observed previously in a cartoon; it is likely

that some adults and adolescents of driving age are similarly influenced by the driving

observed in films and on television.3 Learning to drive from a parent or friend who is

an aggressive driver, or associating with aggressive drivers, also can shape the

behavior. In this regard, Parker et al. (1998) found that drivers who had committed

large numbers of aggressive driving violations were more likely to believe that people

important to them would approve of the behavior, than drivers with few violations.

 

3 Composing this sentence evokes memories of revving engines and squealing tires as vehicles exited the

parking lot following showings of the films, Grand Prix, in 1966, and Bullit, in 1968. Do modern films

have this effect on young drivers?
– 7 –

Much has been written about the erosion of shared values and respect for

authority, variously attributed to the fragmentation of the extended family, increased

individual mobility, media influence, and other characteristics of modern society. It does

appear that civility and respect for authority have diminished, the trend epitomized by

the phrase, “I’m just looking out for number one.”

HABITUAL OR CLINICAL BEHAVIOR

Most motorists rarely drive aggressively, and some never at all. For others, episodes of aggressive driving are frequent, and for a small proportion of motorists it is

their usual driving behavior. Occasional episodes of aggressive driving might occur in

response to specific situations, such as speeding and changing lanes abruptly when late

for an important appointment, when it is not the driver’s normal behavior. Among the

chronic aggressive drivers there are those who learned the driving style and consider it

appropriate, and others who may have learned to drive properly, but for whom the

behavior is an expression of illness. Clearly, it is a matter of degree and not all anger is

uncontrolled, or even inappropriate; that is, it is not the anger, but what a person does

about it that matters (e.g., anger that motivates a person to call the police when

encountered on the road by an obviously impaired or dangerously aggressive driver).

However, chronic anger, habitual or persistent aggressive driving, and especially a

pattern of confrontation on the road, must be considered manifestations of pathology,

in addition to violations of the law.4

The less extreme forms of aggressive driving are better understood, but are we

really experiencing increases in road rage and aggressive driving? The answer is “yes,”

and for the same reason that traffic congestion has increased, as described previously in

the Introduction to this report and summarized in Table 1. That is, even if the

proportions of predisposed and provoked drivers have remained unchanged during

the past decade, 26 percent increases in both road rage and aggressive driving should

be expected from the increase in miles traveled during that period (i.e., a 27 percent

increase in miles traveled minus a one percent increase in new roadway); rate and

incidence of the phenomena are separate measures. If it seems that there are more

cases of rude and outrageous behavior on the road now than in the past, the

observation is correct, if for no other reason than there are more drivers driving more

miles on the same roads than ever before.

SUMMARY OF CONTRIBUTING FACTORS

The preceding discussion addressed only the most salient of the many factors

that might contribute to the incidence of road rage and aggressive driving. Sociologists,

psychologists, psychiatrists, journalists, traffic safety experts, and law enforcement

personnel, among others, all have offered opinions concerning the causes of road rage

and aggressive driving. Some of the suggested causes are more likely to help explain

the behavior than others.

Scott (2002) assembled an inventory of diverse contributing factors to aggressive

driving, ranging from violent video games to increased commuting distances and

durations. We have added to Scott’s inventory of contributing factors, based on the

current research, and present the modified list in Appendix A of this report. The large

 

4

 Perhaps road rage, air rage, and office rage (i.e., “going postal”) are just different versions of the same

phenomenon.
– 8 –

number and diversity of possible causes of aggressive driving implies that the

behaviors are complex and could be influenced by many different predisposing and

provoking factors.
– 9 –

THE PROGRAMS

In the Spring of the year 2000, the National Highway Traffic Safety Administration selected two proposals for funding from a large number of offers to develop and

conduct programs intended to reduce the incidence of aggressive driving. The selected

proposals were submitted 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 moving violations that are associated with

aggressive driving in four 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. Although

the programs shared additional features, program managers were encouraged to

consider innovative approaches to both special enforcement and publicity. The two

programs are summarized in the following pages.

THE MARION COUNTY TRAFFIC SAFETY PARTNERSHIP

The City of Indianapolis is the capital of

Indiana, the largest city in the state, and the

twelfth largest city in the United States of

America. The City of Indianapolis expanded its

borders in 1970 to encompass all 402 square miles

of Marion County, with the exception of several small communities that chose to

remain independent. The U.S. Census Bureau estimates that 857,000 people lived in

Marion County in the year 2001, representing a population increase of 7.5 percent since

1990. Census data show that the population is composed of 70 percent White, 24

percent African American, 4 percent Hispanic, and one percent each of residents who

reported Asian and Native American ancestry. Marion County’s median household

income in 2001 was $45,548 and the median home price was $116,900.

The Marion County Traffic Safety Partnership was formed in 1994 to identify

traffic safety problems and implement mitigating programs for the entire county. The

organization has a small, full-time staff, including a motivated and capable professional

director, and an advisory board composed of concerned citizens, health care

professionals, city council members, insurance managers, the county prosecutor, and

representatives from the Marion County Sheriff’s Office, the Indianapolis Police

Department, and the departments of the several small communities within Marion

County that are surrounded by the City of Indianapolis. The Marion County Traffic

Safety Partnership had conducted large-scale impaired driver and safety restraint

awareness programs, among other activities, prior to being selected by NHTSA to

develop and implement an aggressive driving program.

RUB OUT AGGRESSIVE DRIVING: THE R.O.A.D. TEAM

The Marion County Traffic Safety Partnership selected “Rub Out Aggressive

Driving” as the name for their program and referred to the participating officers in

publicity materials as the “ROAD Team.” As required by their agreement with NHTSA,

the Marion County aggressive driving program comprised both special enforcement

and public information and education.
– 10 –

ENFORCEMENT

The special enforcement component of the program involved deployment of

marked and unmarked police vehicles in areas characterized by the disproportionate

incidence of aggressive driving. A review of crash records led to the identification of

five roadway segments in Indianapolis that would become the special enforcement

zones during the six-month program period.5 The

special enforcement effort focused on drivers who

exhibited two or more 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. Squads of

five officers and a supervisor were assembled from

the participating agencies and deployed during

morning and evening drive times on 61 days during

the six month program period.

The special enforcement effort of the Rub Out Aggressive Driving program was

conducted as overtime activity by a total of 42 officers from six law enforcement

agencies, which included the police departments of Indianapolis, Cumberland,

Lawrence, and Beech Grove, the Marion County Sheriff’s Department, and the Indiana

State Police. The participating officers worked an average of 33 overtime hours each

during the six-month period, with individual participation ranging from four to 76

hours. The Marion County Traffic Safety Partnership’s program devoted a total of 1,400

officer-hours to the special patrols.

PUBLIC INFORMATION AND EDUCATION (PI&E)

The Marion County aggressive driving program implemented an extensive

Public Information and Education (PI&E) component, which included a website,

brochures, 20 billboards announcing the program, and frequent paid advertising on

radio and television stations. The radio and television

“spots” that were developed for the program were

extremely high quality and featured racing celebrities

familiar to residents of the Indianapolis area. Program

managers spent half of their total budget on publicity,

but purchasing air time encouraged station managers

to donate considerable public service time to the

Marion County program, resulting in extensive

publicity by broadcast media. In particular, the

program paid a local television station to broadcast a

30-second PI&E message on 50 occasions during the

first five months of the program period, but records

show that the message was broadcast a total of 125

times. Similarly, the purchase of two hundred radio

spots resulted in additional free air time, and the

aggressive driving program served as a topic of

discussion on drive-time radio “talk shows.”

 

5

 The Marion County program abandoned two of its special enforcement zones at about the mid-point of

the six-month study period.
– 11 –

The Marion County Traffic Safety Partnership issued press releases regularly to

remind the public of the aggressive driving program by announcing the dates and

locations of the special enforcement patrols. Several articles concerning the program

were published in The Indianapolis Star during the study period. The articles were

supportive of the program and usually included tallies of the citations issued. News

coverage also stimulated the publication of letters to the editor, mostly opposed to the

special enforcement effort.

The Marion County aggressive driving program received additional, yet

unfortunate, publicity when a fatal crash occurred during a high speed pursuit by an

officer assigned to the aggressive driving patrol. The duration of the pursuit was fewer

than 30 seconds, but during that brief time the fleeing driver exited highway I-90 into

downtown Indianapolis rush hour traffic, then ran a red light, crashing broadside into

another vehicle; the driver of that vehicle died six days later. The incident generated

controversy and received extensive news coverage because the officer, from a

neighboring community, crossed the jurisdictional boundary into Indianapolis during

the pursuit. Although he announced that the motorist was evading the enforcement

stop, the radio frequency that he used was monitored only by other officers assigned to

the aggressive driving patrol. The circumstances and sad outcome of the incident

focused unwanted attention on the Marion County special enforcement program.6

Program managers in Marion County worked closely with local prosecutors

during the planning and implementation phases of their enforcement program. A

Commissioner of the Traffic Court in Marion County supported the efforts of the

Traffic Safety Partnership by excluding violators from the Safe Driver Program who

officers designated as aggressive drivers; the diversion program typically is available to

drivers who receive a ticket for a moving violation and have had no prior convictions

during the previous two years. The traffic commissioner also regularly imposed a

supplemental fine of $25 when designated aggressive drivers contested their citations.

THE TUCSON POLICE DEPARTMENT

With 487,000 residents in 2001, the City of Tucson is the second largest city in

Arizona, and the center of government for Pima County. The U.S. Census Bureau estimates that 863,000 people lived in Pima County in the year 2001, representing a population increase of 29 percent since 1990. Census data show that the population is composed of 62 percent White, 29 percent Hispanic, 3 percent each of African American

and Native American, and 2 percent who

reported Asian ancestry. Pima County’s

median household income in 2001 was

$45,100 and the median home price was

$124,500.

 

6 Because of the short duration of the pursuit, it is unlikely that notifying the Indianapolis Police

Department’s dispatcher could have affected the outcome. The driver who evaded the enforcement

stop was operating his vehicle on a suspended license and would have gone to jail on that charge. He

fled the scene of the crash on foot and was chased and apprehended by the officer and his K-9 partner

moments later; the officer called for an ambulance for the critically injured motorist during the brief

foot chase. Agency policies concerning high-speed pursuits were scrutinized following the incident.
– 12 –

The Tucson Police Department was formed

in 1871, when the community was part of

the Arizona Territories. The department has

expanded during recent years to a force of

1,000 sworn officers who are responsible for

patrolling the 200 square miles encompassed by the City of Tucson. The Traffic

Section of the Tucson PD is referred to as

the “flagship of the department” because of its high visibility and interaction with the

community. Through education, enforcement and engineering, the Traffic Section is

dedicated to fostering a safe environment for all individuals traveling within the City of

Tucson. The Tucson Police Department had conducted large-scale impaired driver and

safety restraint awareness programs, among other activities, prior to being selected by

NHTSA to develop and implement an aggressive driving program.

WE’VE GOT YOUR NUMBER

The Tucson Police Department selected “We’ve Got Your Number” as the name

for their program, a reference to the telephone number that could be used to report

incidents of aggressive driving to the police department; the “hotline” was the central

component of the Tucson PD’s public information and education program. As required

by their agreement with NHTSA, the Tucson Police Department’s aggressive driving

program comprised both special enforcement and public information and education.

ENFORCEMENT

As in Marion County, the special enforcement component of Tucson’s program

involved deployment of marked and unmarked police vehicles in areas characterized

by the disproportionate incidence of aggressive driving. A review of crash records led

to the identification of four roadway segments within the City of Tucson that would

become the special enforcement zones during the six-month program period. The

special enforcement effort focused 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.

Two officers patrolled the special enforcement zones in unmarked police vehicles, with motorcycle backup nearby, nearly every day throughout the six-month program; two additional officers each patrolled the special enforcement zones in unmarked

vehicles one day per week. That is, the

special enforcement effort of the We’ve

Got Your Number program was conducted as the primary assignment of their

regular-duty shifts by the same two

officers for the duration of the program.

Also, the same two officers augmented the

primary patrols one day each week

throughout the program. The four participating officers devoted a total of 2,400

officer-hours to the special enforcement

effort, on 168 days, during the six-month

program period.
– 13 –

PUBLIC INFORMATION AND EDUCATION (PI&E)

The Tucson PD officers who conducted the special enforcement also developed

and implemented the PI&E component prior to beginning the enforcement period.

With the assistance of department staff, the officers developed brochures, key chains,

pens, and pencils, bumper stickers, 40,000 inserts that accompanied all citations issued,

and 20,000 flyers that were attached to Domino’s pizza boxes. Officers distributed

materials and displayed their unmarked, aggressive driving enforcement vehicles at

several special events, such as Public Safety Appreciation Night at the Tucson

Sidewinders’ baseball stadium. Also, an outdoor advertising company donated ten

billboards located throughout the city to announce the program’s aggressive driving

hotline. And, Alltel Corporation, a mobile telephone provider, donated the service and

answering machine to record reports of aggressive driving.

The Tucson PI&E program did not include paid radio and television advertising.

Rather, officers discussed the aggressive driving program on public-access cable

stations, and invited reporters to ride with them during special patrols. The ride-alongs

resulted in several news stories by local television stations and frequent discussion

during drive-time radio talk shows. The radio hosts continued to announce the hotline

telephone number throughout the six-month program period.

The Tucson PD’s program received considerable free publicity because of the

Aggressive Driving Hotline. Officers announced the hotline and discussed the reasons

for conducting the enforcement program on local radio and television talk shows and

news programs. The report line telephone number was printed on the brochures,

bumper stickers, and other items that were distributed, and it was prominently

displayed on billboards throughout the city. Motorists were encouraged to call the

telephone number to describe serious incidents of aggressive driving and report the

license plate numbers of the vehicles involved. The lieutenant in charge of the program

personally responded to each report of aggressive driving with letters to the caller and

to the registered owner of the offending vehicle. Letters of appreciation were sent to

callers, while owners of offending vehicles received letters that described the incident

and warned that further reports could result in enforcement action. The response to the

hotline was tremendous.

The Aggressive Driving hotline received 87 calls during the first month of

operation and averaged 64 calls per month during the six-month program period.

Lieutenant Martín Moreno, the Tucson PD lieutenant responsible for the program,

reported that many of the people who received warning letters called him to complain,

however, defending their driving behavior usually caused them to realize that they had

acted inappropriately while driving, and in some cases, dangerously. Most of the
– 14 –

conversations ended with a sincere apology and promise to drive with more

consideration in the future. The officers involved in the program were gratified by

these individual responses and consider them to be among the most important

outcomes of their program.

Program managers in Tucson met with their local prosecutors and Municipal

Court Magistrates early in the planning phase of their project to advise court personnel

about the dangers of aggressive driving and to discuss Arizona’s new aggressive

driving statute. Collaboration between law enforcement and the courts resulted in a

standardized plea agreement that ensured uniform prosecution of aggressive drivers,

beginning at implementation of the Tucson police Department’s special enforcement

program.

SUMMARY OF THE PROGRAMS

The overall level of special enforcement effort can be measured by the numbers

of patrol hours, days on which patrols were conducted, and officers deployed. The

agencies participating in the Marion County Traffic Safety Partnership’s program

devoted a total of 1,400 hours to the special patrols, compared to 2,400 officer hours by

the Tucson Police Department. The scheduling and staffing of the special enforcement

patrols also differed. The Marion County program limited deployment of special

patrols to 61 days during the six month program period, compared to 168 days of

special enforcement in the Tucson Police Department’s program. Also, 42 officers from

six law enforcement agencies conducted the Marion County special enforcement

patrols, compared to the same four officers from a single agency in the Tucson

program. The Marion County officers worked an average of 33 overtime hours each

during the six-month period (with individual participation ranging from four to 76

hours). In contrast, two officers of the Tucson Police Department worked full-time on

their program, with two additional officers devoting one day each week to the special

enforcement effort. In other words, the Marion County approach was to deploy several

officers at a time, distributing the hours among 42 officers from six participating

agencies, and to limit the frequency of the patrols to one day in three. The Tucson

approach was to assign the same four officers to the special detail and to conduct the

special enforcement patrols nearly every day of the six month program period.

Other differences between the two programs are revealed by the proportions of

grant funds devoted to the three primary categories of expenditures. In particular, the

Marion County program spent half of its budget on publicity, including frequent paid

advertising on radio and television stations. Purchasing air time encouraged station

managers to donate considerable public service time to the Marion County program, in

addition to the paid spots, resulting in extensive publicity by broadcast media. In contrast, the Tucson program spent only 11 percent of its budget on publicity, relying on

inexpensive flyers, donated billboards, volunteer efforts, and free news coverage of

their program, rather than paying for advertising. The Tucson program spent 40 percent more of its budget on officer labor than did the Marion County program, in order

to support the two full-time officers and schedule of more frequent special enforcement

patrols. Further, the Tucson program spent 22 percent of its budget on equipment,

compared to about two percent in Marion County. The Tucson program purchased an

unmarked patrol car, motorcycle, laser speed gun, and two in-vehicle video systems

with grant funds, while the Marion County program purchased only two in-vehicle

video cameras. Figure 3 illustrates a comparison of program expenditures.
– 15 –

Figure 3. Comparison of Program Costs

48 50

2

67

11

22

0

10

20

30

40

50

60

70

80

Personnel Publicity Equipment

Marion County Traffic Safety Partnership Tucson Police Department

Table 2 presents a summary of the enforcement effort in both aggressive driving

programs. The table lists the numbers of enforcement stops and citations for offenses

associated with aggressive driving (separately) and other offenses (combined) that

were issued by officers in each program. The table shows that the Marion County

officers stopped 1,334 motorists and cited 2,215 offenses, for an average of 1.7 offenses

per enforcement stop. Officers of the Tucson program made 1,907 enforcement stops

and cited 2,383 offenses, for an average of 1.3 offenses per stop. The difference in

average number of offenses per stop reflects the Marion County program’s emphasis

on citing motorists who exhibited two or more offenses that are associated with

aggressive driving.

TABLE 2

SUMMARY OF ENFORCEMENT EFFORT BY THE TWO AGGRESSIVE DRIVING PROGRAMS

Marion County Traffic Tucson

Offense Safety Partnership Police Department

Aggressive Driving 568* 56**

Speeding 916 1,343

Following Too Closely 244 97

Unsafe Lane Change 173 57

Failure to Yield Right of Way 22 32

Other 745 742

Total Violations Cited 2,215 2,383

Total Number of Stops 1,334 1,907

*The 568 offenses are not included in the Marion County total because Aggressive Driving is a

designation made by officers to represent the severity of an infraction (usually two or more infractions).

**The 56 aggressive driving offenses listed for Tucson are included in the Tucson total because

aggressive driving is a separate offense in Arizona.
– 16 –

The key elements of the two aggressive driving programs and maps indicating

the locations of the special enforcement zones are presented below.

Marion County Traffic Safety

Partnership “R.O.A.D. Team Program”

Tucson Police Department

“We’ve Got Your Number Program”

Enforcement

3 special enforcement zones;

6 local law enforcement agencies;

1,394 officer-hours devoted to the special

patrols;

Special enforcement conducted on 61 days

during the 6 month program period.

Tactics: Squads of five officers deployed to

the special enforcement zones during

morning and evening commuting periods

on selected days to focus on vehicles

exhibiting two or more aggressive

driving violations. Experimented with

police helicopters but ground units could

not reach offenders.

Publicity

Press releases

Posters

Brochures

Outdoor display advertising

Corporate Campaign (links to companies)

Television and radio paid advertising

Television and radio public service

announcements

Several articles in the Indianapolis Star

Enforcement

4 special enforcement zones;

1 law enforcement agency;

2,400 officer-hours devoted to the special

patrols;

Special enforcement conducted on 168

days during the 6 month program period.

Tactics: Two officers were assigned fulltime responsibility to patrol the special

enforcement zones in unmarked police

vehicles (with motorcycle backup nearby)

nearly every day throughout the

program; two additional officers each

deployed in unmarked vehicles one day

per week.

Publicity

Pizza boxtop flyers

Flyers distributed to motorists

Outdoor display advertising

Bumper stickers

Ride-alongs by news reporters

Television and radio coverage of the

program

Special events displays

Aggressive Driver Hot Line
– 17 –
– 18 –
– 19 –

PROGRAM RESULTS

The primary measures of program effects for this evaluation of aggressive

driving countermeasures are, 1) samples of vehicle speeds, and 2) the incidence of

crashes in the special enforcement zones. Program results are presented in these two

categories in the following paragraphs.

SPEED SAMPLES

One-hour samples of vehicle speed were taken unobtrusively at the same

locations, beginning at least one month prior to program implementation. Speed

samples were obtained by use of lidar devices at the same locations, during the same

weeks of the month, and for each location, on the same day of the week and the same

hour of the day (to maximize comparability). Data collectors were instructed to

postpone sampling one week if it appeared that rain at a scheduled sampling time

would affect vehicle speeds. Program personnel in Marion County and Tucson

interpreted the speed sample requirement differently, resulting in non-uniform baseline

periods and slightly different sampling schedules. However, data collectors for both

programs followed the same sampling procedures and used identical data collection

forms.

MARION COUNTY SPEED SAMPLE RESULTS

The Marion County special enforcement program was conducted from March 1

through August 31, 2001. Program personnel collected speed samples at five locations,

beginning approximately three months prior to the start of the program and

continuing throughout the six-month program period. Samples consisted of 105 vehicle

speeds for each location and date. Data collection forms were sent to Anacapa Sciences,

Inc., for data entry and analysis. The following three figures, collectively labeled as

Figure 4, illustrate the results of the analysis, presenting the average vehicle speed and

the highest speed recorded on each sampling date; the shaded areas indicate the

baseline period (i.e., samples taken prior to program implementation). Each figure

represents a separate sampling location. Marion County began with five special

enforcement zones, but program managers abandoned locations A and E mid-way

through the program.

Table 3 summarizes the speed sample results illustrated in the figures. The table

shows that average speeds during the program period were slightly lower than during

the baseline periods at two of the sites, and slightly higher at the third sites. The

average of the averages shows a one percent decline in speed, overall. However, this

calculation could be misleading if the different posted speed limits at the locations

differentially influence drivers’ responses to the special enforcement program; although

this does not appear to be the case, averages of averages could obscure program

effects.7 For this reason, an alternative measure is to sum the percent change values for

the three sampling sites that were within the program’s three special enforcement

zones: Site B declined by one percent, Site C declined by three percent, and Site D

increased by one percent, for an overall decline in average speed of three percentage

points in Marion County’s special enforcement zones.

 

7

 The special enforcement zone with the 40 mph speed limit declined by one percent, while one of the 35

mph zones declined by three percent and the other increased by one percent.
– 20 –

Location B: 5300 W. 38th St. (40 mph Limit) 

40

45

50

55

60

65

Average Speed High Speed

Baseline Period Program Period

Location C: 5600 N. Keystone Ave. (35 mph Limit)

36

41

46

51

56

61

66

71

Average Speed High Speed

Baseline Period Program Period

Location D: 2800 E. Washington St. (35 mph Limit)

38

43

48

53

58

63

Average Speed High Speed

Baseline Period Program Period

TABLE 3

MARION COUNTY UNOBTRUSIVE SPEED SAMPLES:

COMPARISON OF AVERAGE OF BASELINE SAMPLES TO

AVERAGE OF SAMPLES DURING THE PROGRAM PERIOD, IN MILES PER HOUR

Speed Average Speed Average Speed Percent

Site Limit Baseline Period Program Period Change

B 40 45.68 45.03 -1%

C 35 41.67 40.62 -3%

D 35 40.50 41.02 +1%

Average of All 3 Sites 42.62 42.22 -1%

Sum of Change Values -3%

TUCSON SPEED SAMPLE RESULTS

The Tucson special enforcement program was conducted from July 1 through

December 31, 2001. Program personnel collected speed samples at four locations,

beginning in January and continuing throughout the six-month program period.

Samples consisted of between 686 and 1,274 vehicle speeds for each location and date.

Data were entered by program personnel and sent to Anacapa Sciences, Inc., for

analysis. The following four figures, collectively labeled as Figure 5, illustrate the results

of the analysis, presenting the average vehicle speed and the highest speed recorded on

each sampling date; the shaded areas indicate the baseline period (i.e., samples taken

prior to program implementation). Each figure represents a separate sampling location.

Each location was within one of the four zones on which the Tucson Police Department

focused its special enforcement efforts.

Figure 4. Marion County speed sample results.
– 21 –

Table 4 summarizes the speed sample results illustrated in the figures. The table

shows that average speeds during the program period were slightly higher than during

the baseline periods at one of the sites, slightly lower at two of the sites, and

substantially lower at one of the sites. The average of the averages shows a three

percent decline in speed, overall. But, as before, calculating the averages of averages

could obscure program effects. Summing the percent change values for the four

sampling sites, all of which were within the program’s four special enforcement zones,

again provides a more appropriate measure: Site 1 declined by nine percent, Site 2

declined by three percent, Site 3 increased by one percent, and Site 4 declined by two

percent, for an overall decline in average speed of 13 percentage points in Tucson’s

special enforcement zones.

Location 1: Oracle/River Road (40 mph Limit)

25

30

35

40

45

50

55

60

65

70

Jan.-

Feb.

March April May June July August Sept. Oct. Nov. Dec.

Average Speed High Speed

Baseline Period Program Period

Location 2: Golflinks/Swan (45 mph Limit)

35

40

45

50

55

60

65

70

75

80

Jan.-

Feb.

March April May June July August Sept. Oct. Nov. Dec.

Average Speed High Speed

Baseline Period Program Period

Location 3: Speedway/Palo Verde (35 mph Limit)

35

40

45

50

55

60

65

70

75

80

Jan.-

Feb.

March April May June July August Sept. Oct. Nov. Dec.

Average Speed High Speed

Baseline Period Program Period

Location 4: Swan to City Limits (40 mph Limit)

35

40

45

50

55

60

65

70

75

80

Jan.-

Feb.

March April May June July August Sept. Oct. Nov. Dec.

Average Speed High Speed

Baseline Period Program Period

Figure 5. Tucson speed sample results.

TABLE 4

TUCSON UNOBTRUSIVE SPEED SAMPLES:

COMPARISON OF AVERAGE BASELINE SPEEDS TO

AVERAGE SPEEDS DURING THE PROGRAM PERIOD, IN MILES PER HOUR

Speed Average Speed Average Speed

Site Limit Baseline Period Program Period Change

1 40 37.47 34.22 -9%

2 45 47.38 45.87 -3%

3 35 38.23 38.63 +1%

4 40 46.60 45.86 -2%

Average of All 4 Sites 42.42 41.15 -3%

Sum of Change Values -13%
– 22 –

CRASH DATA

MARION COUNTY CRASH RESULTS

Crash data were provided by the City of Indianapolis for the three special

enforcement zones and three comparable locations that did not receive special

aggressive driving enforcement effort. Data for each location were provided, by month

for the program period, the same six-month period one year earlier, and for the

intervening six-month period (i.e., an 18-month series beginning one year prior to

program implementation). Data were entered in configured spreadsheets and included

designations of crash severity (Fatal, Injury, and Property Damage Only/PDO) and

primary collision factor (PCF). The following three figures, collectively labeled as Figure

6, illustrate the crash frequencies, presenting the numbers of injury and PDO crashes in

each of the Marion County special enforcement zones during the program period in

2001 and in the same six-month period of the Year 2000; the shaded areas indicate the

intervening six-month period.8

Location B: W. 38th Street

0

5

10

15

20

25

30

March April May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001 

Location C: N. Keystone Ave.

0

5

10

15

20

25

March April May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001

Figure 6. Crashes in the Marion County special

enforcement zones.

Table 5 presents a summary of all crash data relevant to the Marion County

aggressive driving program. The table shows that the three special enforcement zones

and the three comparison zones experienced substantial increases in both injury and

PDO crashes during the program period, compared to the same six-months of the

previous year. The increases ranged from a six percent increase in injury crashes in the

comparison zones to a 39 percent increase in PDO crashes in the special enforcement

zones. Overall, crashes increased by 32 percent in the special enforcement zones and 24

percent in the comparison zones. The table also shows that the numbers of crashes for

which a PCF associated with aggressive driving was cited increased by 21 percent in the

comparison zones and by nearly twice that rate in the special enforcement zones.9

 

8

 Corresponding figures for the Marion County Comparison Zones are included in Appendix B.

9 The Primary Collision Factors (PCFs) associated with aggressive driving are, Unsafe Speed, Failure

to Yield Right-of-Way, Disregarded Signal/Sign, Left of Center, Improper Passing, Improper Turning,

and Following Too Closely.

Location D: N. Washington Street

0

5

10

15

20

March April May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001
– 23 –

TABLE 5

SUMMARY OF ALL CRASH MEASURES DURING THE PROGRAM PERIOD AND THE SAME SIX-MONTH

PERIOD ONE YEAR EARLIER: MARION COUNTY SPECIAL ENFORCEMENT AND COMPARISON ZONES

March-Aug. 2000 March-Aug. 2001 Percent

Measure Comparison Period Program Period Change

Total PDO Crashes in Enforcement Zones 178 248 +39%

Total PDO Crashes in Comparison Zones 177 238 +34%

Total Injury Crashes in Enforcement Zones 81 95 +17%

Total Injury Crashes in Comparison Zones 103 109 +6%

Total Crashes in Enforcement Zones 259 343 +32%

Total Crashes in Comparison Zones 280 347 +24%

Total Target PCFs in Enforcement Zones 160 226 +41%

Total Target PCFs in Comparison Zones 196 238 +21%

Percent of Crashes w/ a Target PCF: Enforcement 62% 66% +6%

Percent of Crashes w/ a Target PCF: Comparison 70% 69% -1%

The substantial increases in the numbers of crashes in the comparison zones, and

even greater increases in the special enforcement zones, suggest the influence of factors

that were outside the control of the quasi-experiment. For example, a disproportionate

number of rainy days or increased traffic volumes during the program period might be

responsible for the increase in crash incidence; these issues will be discussed in a

subsequent section of this report. However, calculating the proportions of all crashes

with a primary collision factor associated with aggressive driving, for the program and

comparison periods, largely eliminates the effects of uncontrolled variables that might

influence the incidence of crashes; that is, in the current context, comparing the

proportions of aggressive driving-related crashes is more meaningful than comparing

the actual numbers of crashes. The results of these calculations, presented in Table 5,

show that the proportions of all crashes in the enforcement zones that were associated

with aggressive driving increased by about six percent. In contrast, the overall incidence

of crashes in those zones increased by 32 percent. The proportions of all crashes in the

comparison zones that were associated with aggressive driving remained the same,

despite a 24 percent increase in crashes, overall, in the comparison zones.

TUCSON CRASH RESULTS

Crash data were provided by the City of Tucson for the four special enforcement

zones and four comparable locations that did not receive special aggressive driving

enforcement effort. Data for the special enforcement zones were provided by month

for the program period, the same six-month period one year earlier, and for the intervening six-month period (i.e., an 18-month series beginning one year prior to program

implementation). Crash data for the comparison zones were provided for the two sixmonth periods, rather than by month. Data were entered in configured spreadsheets

and included designations of crash severity (Fatal, Injury, and Property Damage

Only/PDO) and primary collision factor (PCF). The following four figures, collectively

labeled as Figure 7, illustrate the crash frequencies, presenting the numbers of injury

and PDO crashes in each of the Tucson special enforcement zones during the program

period in 2001 and in the same six-month period of the Year 2000; as in the previous

figures, the shaded areas indicate the intervening six-month period.
– 24 –

Location 1: Oracle

0

2

4

6

8

10

12

14

July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001

Location 2: Golflinks

0

1

2

3

4

5

6

7

8

July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001

Location 3: Speedway

0

1

2

3

4

5

6

7

July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001

Location 4: Swan

0

2

4

6

8

10

12

July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001

Figure 7. Crashes in the Tucson special enforcement zones.

Table 6 presents a summary of all crash data relevant to the Tucson aggressive

driving program. The table shows that the four special enforcement zones and the four

comparison zones experienced increases in PDO crashes and declines in injury crashes

during the program period, compared to the same six-months of the previous year.

The changes ranged from a 20 percent increase in PDO crashes in the enforcement

zones to a 15 percent decrease in injury crashes in the comparison zones. Overall,

crashes increased by 10 percent in the special enforcement zones and decreased by two

percent in the comparison zones. The table also shows that the numbers of crashes for

which a PCF associated with aggressive driving was cited decreased by three percent in

the comparison zones and by nearly three times that rate in the special enforcement

zones.
– 25 –

TABLE 6

SUMMARY OF ALL CRASH MEASURES DURING THE PROGRAM PERIOD AND THE SAME SIX-MONTH

PERIOD ONE YEAR EARLIER: TUCSON SPECIAL ENFORCEMENT AND COMPARISON ZONES

July-Dec. 2000 July-Dec. 2001 Percent

Measure Comparison Period Program Period Change

Total PDO Crashes in Enforcement Zones 84 101 +20%

Total PDO Crashes in Comparison Zones 86 92 +7%

Total Injury Crashes in Enforcement Zones 61 59 -3%

Total Injury Crashes in Comparison Zones 62 53 -15%

Total Crashes in Enforcement Zones 145 160 +10%

Total Crashes in Comparison Zones 148 145 -2%

Total Target PCFs in Enforcement Zones 121 122 +1%

Total Target PCFs in Comparison Zones 104 98 -6%

Percent of Crashes w/ a Target PCF: Enforcement 83% 76% -8%

Percent of Crashes w/ a Target PCF: Comparison 70% 68% -3%

PROGRAM AWARENESS

The managers of both aggressive driving programs were encouraged to conduct

surveys of public awareness to determine if local drivers received the programs’ public

information and education messages. The Tucson Police Department did not conduct a

survey; rather, the officers interpreted the response to their aggressive driver hotline as

evidence of substantial public awareness. In contrast, the managers of the Marion

County program commissioned Purdue University’s Center for the Advancement of

Transportation Safety to conduct identical telephone surveys of 100 drivers each, prior

to and at the conclusion of the Marion County Rub Out Aggressive Driving program.

The Marion County pre- and post-program surveys contained 72 questions, the subjects of which ranged from demographic information to opinions about hypothetical

changes to the Indiana vehicle code. Only two questions addressed public awareness of

the aggressive driving program. The first of those questions asked, “Besides your

experiences of aggressive driving while driving or as a passenger, what is your level of

awareness of aggressive driving as a potential problem?” The responses to this question are presented in Table 7.

TABLE 7

RESPONSES TO THE MARION COUNTY PUBLIC AWARENESS SURVEY QUESTION #1

Response Pre-Program Post-Program

I read or hear about it on a daily basis. 15.1% 13.0%

I read or hear about it on a weekly basis. 32.6% 27.0%

I have read or heard about it at least once in the past month. 39.5% 33.0%

I have read or heard about it at least once in the past six months. 7.0% 15.0%

I have not read or heard anything about it until this interview. 5.8% 11.0%
– 26 –

The table shows that, overall, fewer drivers reported awareness of aggressive

driving as a problem at the conclusion of the Marion County program than before it

began. Fewer drivers reported hearing about the issue on a daily or weekly basis and

within the past month, despite the extensive advertising campaign implemented by the

Marion County Traffic Safety Partnership. Evidence that some drivers heard or read at

least something about aggressive driving can be found in the 15 percent of respondents

who reported hearing about the issue at least once during the past six months, up from

seven percent prior to the program period. However, 11 percent reported that they

had never heard or read anything about aggressive driving until the survey interview,

compared to about six percent before the PI&E program.

The other relevant question on the survey asked about the primary sources of

the respondents’ awareness of aggressive driving. Table 8 shows that television was the

primary source of information both before and at the conclusion of the Marion County

aggressive driving program. Awareness from newspapers showed the largest change,

increasing as the primary source of information from 16 percent of respondents prior

to the program to 31.5 percent at its conclusion. This increase probably reflects the

Indianapolis Star’s substantial coverage of the program and of the fatal crash that

resulted from a high-speed pursuit by an officer on special enforcement patrol.

TABLE 8

RESPONSES TO THE MARION COUNTY PUBLIC AWARENESS SURVEY QUESTION #2

Response Pre-Program Post-Program

Newspapers/magazines 16.0% 31.5%

Television 42.5% 47.2%

Radio 14.2% 4.5%

Other people 27.4% 14.6%

Other sources 0 2.2%
– 27 –

IMPLICATIONS

The data presented in the previous section of this report show that more crashes

occurred during the program periods in both Marion County and Tucson than in the

same six-month periods of the previous year, when no special aggressive driving

enforcement was conducted in either community. Marion County’s special enforcement

zones experienced 32 percent more crashes than during the same period of the Year

2000; crashes in Tucson’s special enforcement zones increased by ten percent, overall.

Further, in Marion County, crashes with primary collision factors associated with

aggressive driving increased by 21 percent in the comparison zones and by 41 percent

in the special enforcement zones. Based on increases such as these, it would be

reasonable to question whether special enforcement has a stimulating, rather than an

inhibiting, effect on the incidence of aggressive driving. One interpretation might be

that the special enforcement and PI&E programs influenced some motorists to drive

more slowly, resulting in increased opportunities for aggressive drivers, whose

behavior is less likely to be influenced by the programs, to overtake the slower drivers,

with the encounters leading to the increase in crashes.

The Introduction to this report discussed the apparent increase in road rage and

aggressive driving, and attributed the increase in observed incidents, largely, to the 27

percent increase in vehicle miles traveled per year that occurred in the U.S. during the

final decade of the Twentieth Century. With the addition of only one percent of

roadway during that period, one might expect, overall, 26 percent increases in all trafficrelated phenomena, or increases of approximately two and a half percent each year in

the absence of mitigating factors. However, the relationship between traffic volume

and phenomena such as crashes may not be linear, nor are increases in traffic volume

uniformly distributed throughout the network of roads and highways. That is, a small

increase in traffic volume from one year to the next might result in a disproportionate

change in crash incidence. Further, changes in traffic volumes are of greater magnitude

on some roadways than on others. Perhaps factors such as these influenced the results

of the aggressive driving programs conducted by the Marion County Traffic Safety

Partnership and the Tucson Police Department.

Data were obtained from the Department of Public Works of the City of

Indianapolis, and the Department of Transportation of the City of Tucson, to determine

if any changes in traffic volumes were measured that might help explain the increases in

crashes that occurred during the program periods. Traffic counts are not performed

every year nor in all locations within a community. For these reasons, in some cases

extrapolation was required from 1999 data and in others from sections of roadway

adjacent to a special enforcement zone. Table 7 presents the estimated changes in traffic

volumes in the Marion County and Tucson special enforcement zones from the Year

2000 to 2001, based on the traffic count data provided by the cities. The table shows that

Marion County’s zones experienced estimated increases in traffic volumes ranging

from five to ten percent, with an average estimated increase of eight percent. The

estimated traffic volume increases in Tucson’s zones ranged from five to 18 percent,

with an average estimated increase of nine percent. The actual and estimated traffic

count data show that the special enforcement zones of both aggressive driving

programs experienced increases in traffic volumes substantially greater than the

national average of two and a half percent between the Year 2000 and 2001.
– 28 –

TABLE 9

ESTIMATED CHANGES IN TRAFFIC VOLUMES

IN THE MARION COUNTY AND TUCSON SPECIAL ENFORCEMENT ZONES: YEAR 2000 TO 2001

Speed Limit Percent Change

Program / Zone (in mph) in Traffic Volume

Marion County Special Enforcement Zones

B 40 +5%

C 35 +8%

D 35 +10% 

Average Change of Traffic Volume +8%

Tucson Special Enforcement Zones

1 40 +5%

2 45 +2%

3 35 +10%

4 40 +18% 

Average Change of Traffic Volume +9%

The estimated increases in traffic volumes are supported by the anecdotal

accounts of officers. Officers of the Marion County program reported that traffic has

been increasing steadily for several years, with a noticeable increase in traffic in the

special enforcement zones during 2001. Officers attribute the increased traffic in the

enforcement zones to two major highway maintenance projects that caused many

motorists to take surface streets to avoid delays on the highways; the maintenance

work was not anticipated by the research plan. Tucson officers also reported noticeable

increases in traffic volumes during 2001. The officers attribute the increases to the recent

expansion of activities at a local Air Force base, which is adjacent to one of the special

enforcement zones, and the construction of several thousand new houses north of the

city. The primary arterial that links the new housing to the city passes through one of

the Tucson Police Department’s special enforcement zones.

The estimated increases in traffic volumes between the years 2000 and 2001

provide a partial explanation for the increases in crashes in the special enforcement

zones of both communities during their aggressive driving programs. The estimated

nine percent increase in traffic volume in Tucson’s zones was accompanied by a ten

percent increase in crashes. An increase in crash incidence comparable to the increase in

traffic volume is a reasonable expectation. The data from Marion County, however, are

not as easily explained.

It was estimated that traffic volume increased by an average of eight percent in

Marion County’s special enforcement zones, while the number of crashes increased 32

percent during the aggressive driving program, compared to the number of crashes

during the same six-month period one year earlier. That is, crashes increased at a rate

four times the increase in traffic volume. The most likely explanation for this difference

is that the estimates of traffic volume are inaccurate; in particular, the extrapolations

from previous years and neighboring zones were statistical projections that did not

take into account any unmeasured increases in traffic volume resulting from the

highway maintenance and construction projects that were mentioned by officers as a

possible explanation for the increase in crashes.
– 29 –

The number of crashes overall is not the primary figure of merit for evaluating

the aggressive driving programs. Increases in traffic volume can result in increased

crash incidence, as discussed in the previous paragraphs. More relevant measures of

program effect are the numbers of crashes with primary collision factors that are

associated with aggressive driving, and the calculated proportions of all crashes that

were assigned those PCFs on collision reports. In this regard, the incidence of crashes

with aggressive driving PCFs might increase, but to demonstrate program effect the

increase cannot be greater than the increase in crashes, overall.

Table 8 presents a summary of the relevant crash data for both Marion County

and Tucson. The table shows that the total number of crashes in the Marion County

special enforcement zones increased by 32 percent, and the number of those crashes

with aggressive driving PCFs increased by 41 percent, as reported previously. That is,

the total number of crashes increased substantially, but the crashes with aggressive

driving PCFs increased at a greater rate. Crashes with the target PCFs is a more

relevant metric than total crashes, but change in the proportion of crashes with the target

PCFs provides the best overall measure of program effect because it eliminates the

influence of differential traffic volume and other uncontrolled factors that might

contribute to an overall increase in crash incidence. In this regard, Table 8 shows that

the Marion County zones experienced a six percent increase in the proportion of all

crashes with aggressive driving PCFs; that is, total crashes increased by 31 percent,

crashes with aggressive driving PCFs increased by 41 percent, but the proportion of total

crashes with aggressive driving PCFs increased by six percent.

TABLE 10

SUMMARY OF KEY CRASH MEASURES DURING THE MARION COUNTY AND TUCSON

PROGRAM PERIODS AND THE SAME SIX-MONTH PERIODS ONE YEAR EARLIER

Year 2000 Year 2001 Percent

Program / Measure Comparison Period Program Period Change

Marion County

Total Crashes in Enforcement Zones 259 343 +32%

Total Crashes in Comparison Zones 280 347 +24%

Total Target PCFs in Enforcement Zones 160 226 +41%

Total Target PCFs in Comparison Zones 196 238 +21%

Percent of Crashes w/ a Target PCF: Enforcement 62% 66% +6%

Percent of Crashes w/ a Target PCF: Comparison 70% 69% -1%

Estimated Average Change in Traffic Volume +8%

Tucson

Total Crashes in Enforcement Zones 145 160 +10%

Total Crashes in Comparison Zones 148 145 -2%

Total Target PCFs in Enforcement Zones 121 122 +1%

Total Target PCFs in Comparison Zones 104 98 -6%

Percent of Crashes w/ a Target PCF: Enforcement 83% 76% -8%

Percent of Crashes w/ a Target PCF: Comparison 70% 68% -3%

Estimated Average Change in Traffic Volume +9%
– 30 –

Table 8 also shows that 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. Most 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. In the absence of a countermeasure program, it would be reasonable to expect

a ten percent increase in aggressive driving PCFs, corresponding to the ten percent

increase in crashes, overall, and no change in the proportion of all crashes with the

target PCFs. However, the number of crashes increased in Tucson while the proportion

of those crashes with the target PCFs declined, which suggests that the Tucson Police

Department’s program had an effect on the driving behavior of local motorists.

Greater crash incidence in the enforcement zones could be expected because

those locations were selected on the basis of disproportionate aggressive driving.

Enforcement and comparison zones experienced comparable numbers of crashes

during the preceding year, but the locations of greatest concern to the officers in both

communities were selected to be the enforcement zones. Table 8 also shows that total

crashes and crashes with the target PCFs increased in the Marion County comparison

zones (24 and 21 percent, respectively), but the increases were not as great as in Marion

County’s enforcement zones. The proportion of all crashes with the target PCFs

declined by one percent in the comparison zones and increased by six percent in the

zones in which Marion County’s special enforcement was conducted. Tucson’s

comparison zones experienced two percent fewer crashes during the program,

compared to the same six-month period one year earlier, while crashes in Tucson’s

enforcement zones increased by ten percent. However, the proportion of all crashes

with the target PCFs declined by three percent in Tucson’s comparison zones and by

eight percent in the zones that received special enforcement.

The data summarized in Table 5 showed that Marion County’s 32 percent overall

increase in crashes is composed of a 39 percent increase in property damage only (PDO)

crashes and a 17 percent increase in injury crashes. In contrast, Tucson’s ten percent

overall increase in crashes is composed of a 20 percent increase in PDO crashes and a

three percent decrease in injury crashes. Higher vehicle speed is a more likely

contributing factor to injury crashes than to PDO crashes. Injury crashes increased in

Marion County’s special enforcement zones, but declined in Tucson’s zones, which

suggests greater effectiveness of Tucson’s countermeasure program. This interpretation

of the crash data is supported by the results of the speed samples presented in Tables 3

and 4. Average speeds declined slightly in Marion County, and at a greater rate in

Tucson, possibly in response to special enforcement and other programmatic efforts. 10

EXPLANATION

The original purpose of this report was to present, rather than compare, the two

aggressive driving programs. However, comparisons are inevitable and the

substantially different results of the two programs require an explanation. First, it is

important to understand that it is impossible to control all of the variables that could

influence the outcome of a study when conducting large-scale, quasi-experiments, such

 

10 Baseline speeds were generally faster in Marion County than in Tucson. Average baseline speeds in 35

mph zones were 6.1 mph over the limit in Marion County, compared to 3.7 mph in Tucson; average

speeds in 40 mph zones were 5.3 mph over the limit in Marion County, compared to 2 mph in Tucson. The

causes and possible effects of the apparent differences in baseline speeds are unknown.
– 31 –

as the programs described in this report. Highway maintenance projects and large

residential developments that increase traffic volumes on surface streets are examples

of unexpected and uncontrolled variables that can affect dependent measures in a field

study involving driver behavior. We have attempted to identify and/or control

relevant variables within each program, but the research was not originally designed to

support systematic comparisons between the two programs. Marion County, Indiana,

and Tucson, Arizona, are different in many ways, and it is possible that some of those

differences could be responsible for the differential results reported here.

Despite the differences between Marion County and Tucson, comparisons can be

made if it is assumed that any unknown differences are unlikely to influence the

incidence of crashes or average vehicle speed, and that known differences have been

identified and controlled. For example, a hypothetical difference, such as driving style,

or a known difference, such as climate, are rendered irrelevant by comparing percent

changes from baseline conditions at each location, rather than comparing actual crash

frequencies; this procedure permits comparisons of zones with different baseline crash

frequencies within a program, and comparisons of programs. Also, we calculated the

proportions of crashes with aggressive driving PCFs to facilitate comparisons by

eliminating the confounding effects of increased numbers of crashes, overall. These

methods provide reasonable assurance that the only relevant independent variables are

the components of the two countermeasure programs.

If the assumptions concerning comparability are accepted, the data presented in

this report show that Tucson’s aggressive driving program achieved the intended result

of reducing the incidence of aggressive driving, while the Marion County program did

not. As described previously, each program received a grant of $200,000, but the

managers of the Tucson program devoted considerably more of their resources to

enforcement effort than the Marion County managers, and considerably less to

conventional paid advertising to publicize their program. Further, the Tucson program

assigned two officers full-time and two officers part-time to conduct the special

enforcement patrols and deployed the officers nearly every day of the six-month

program period. In contrast, special enforcement in the Marion County program was

conducted as overtime duty by 42 officers from six different law enforcement agencies,

with teams of five officers deploying, on average, one day in three.

This comparison of the Marion County and Tucson aggressive driving programs

suggests that limited resources might be better spent on officer labor than on publicity.

It also appears that focusing enforcement responsibility on a small team assigned fulltime to the special enforcement patrols is probably more effective than sharing the

responsibility among a large number of officers as occasional overtime duty.

WHY AREN’T THE PROGRAMS MORE EFFECTIVE?

The proportion of all crashes with aggressive driving primary collision factors

increased by six percent in Marion County’s special enforcement zones and decreased

by eight percent in Tucson’s zones. Why didn’t the considerable efforts of both

programs have greater inhibiting effects on driving behavior, as measured by speed

samples and crashes with aggressive driving PCFs? No positive effect of the Marion

County program was measured, and there was only an eight percent decline in the

proportion of aggressive driving crashes in Tucson. It is possible that the programs

were more effective than indicated by the data presented here, but our measures are

insensitive to the change in driving behavior. Or, perhaps we expect too much.
– 32 –

The Introduction to this report identified the driving behaviors and primary

collision factors that are associated with aggressive driving, and used in the current

analysis as measures of program effect. As noted in that discussion, those driving

behaviors and the associated PCFs are imperfect dependent measures because they are

not always the results of conscious decisions to drive aggressively. Rather, unknown

proportions of crashes assigned the “aggressive driving” PCFs clearly are attributable

to inattention and errors in judgment, rather than volitional aggressive driving. For this

reason, programs intended to reduce the incidence of crashes caused by these driving

behaviors can be expected to influence only the portion of those crashes that results

from volitional acts, rather than human error and misjudgment.

Both programs were well planned and conducted by skilled and highlymotivated professionals. It is quite likely that at least Tucson’s countermeasure

program achieved as much success as reasonably can be expected based on the actual,

rather than the news media-inflated, magnitude of the “aggressive driving problem.”

Further, Tucson’s eight percent decline in the proportion of crashes with aggressive

driving PCFs is a considerable accomplishment. The eight percent decline represents

approximately 13 fewer crashes in the special enforcement zones during the six-month

program period than would have occurred had the program not been conducted (i.e.,

five injury crashes and eight property damage only crashes). Some portion, if not all of

those prevented crashes, could be attributable to the Tucson program. Although

statistical tests were not conducted, all measures are consistent with the hypothesis that

a program that combines special enforcement with publicity about the enforcement can

change driver behavior. Economists have calculated the overall costs resulting from

crashes of different severity. The savings to society from preventing eight PDO crashes

and five crashes with only moderate injuries to one person per crash greatly exceeds

the cost of Tucson’s aggressive driving program.

RECOMMENDATIONS

The current study used direct, unobtrusive measures of vehicle speed, and

indirect, archival measures of crash incidence to assess program effects. Both of these

methods produce quantifiable data that are easily obtained and linked to the behavior

of interest. However, not all incidents of aggressive driving result in crashes, and not all

crashes with “aggressive driving” PCFs are caused by aggressive driving. As stated

previously, the methods used in this evaluation are imperfect and might be insensitive

to the accurate measurement of aggressive driving.

Based on the experiences of the current study, it is recommended that observational methods also be used in future evaluations of aggressive driving countermeasure programs. In particular, trained data collectors, positioned unobtrusively at

roadside or at intersections, could record observed incidents of aggressive driving on

paper or electronic forms. The observers would have the advantage of actually seeing

the drivers and the surrounding traffic and, thus, be able to discriminate, in most cases,

whether the behavior was intentional or the result of human error or misjudgment.

Observations conducted according to a systematic sampling plan, involving time of day,

day of week, and location, could provide robust data sets for comparing baseline to

treatment conditions. Direct observation of the behaviors in question would help interpret and allow greater confidence in study results.
– 33 –

ACKNOWLEDGMENTS

We are grateful for the efforts of Ann Stickford and Lieutenant Don Bickel of the

Marion County Traffic Safety Partnership, and Lieutenants Martín Moreno and Brett

Klein, Sergeant Frank Greene, and Officers John Parris and Chris Morand of the Tucson

Police Department.
– 34 –
– 35 –

REFERENCES

Boyle, J., Dienstfrey, S., and Sothoron, A. National Survey of Speeding and Other Unsafe

Driving Actions, Volume II: Driver Attitudes and Behavior. National Highway Traffic

Safety Administration, Washington, DC, Report DOT-HS-808-749, September 1998.

Ellison, P.A., Govern, J.M., Petri, H.L., and Figler, H.M. Anonymity and Aggressive

Driving Behavior: A Field Study. Journal of Social Behavior and Personality, 10, 265-

272, 1995.

Ferguson, A. Road Rage. Time, 151(1), January 12, 1998.

Gulledge, J.D. Victim Visibility as an Inhibitor of Horn Honking Aggression in Traffic.

http://www.mwsc.edu/psychology/research/psy302/fall96/jerry_gulledge.html

December 1996.

Mizel, L. Aggressive Driving. In, Aggressive Driving: Three Studies. AAA Foundation for

Traffic Safety, Washington, DC, March 1997.

Parker, D., Lajunen, T., and Stradling, S. Attitudinal Predictors of Interpersonally

Aggressive violations on the Road, Transportation Research Part F, pp. 11-24, 1998.

Scott, K.M. The Phenomenon of Road Rage: Complexities, Discrepancies, and

Opportunities for CR Analysis. The Online Journal of Conflict Resolution, Issue 3.3,

Fall 2000.

STPP. High Milage Moms. Report by the Surface Transportation Policy Project, July

2002.
– 36 –
– 37 –

APPENDIX A

CONTRIBUTING FACTORS TO AGGRESSIVE DRIVING
– 38 –
– 39 –

CONTRIBUTING FACTORS TO AGGRESSIVE DRIVING

The items on the following list have been suggested in news accounts, scholarly

articles, or the current research as factors that can contribute to the incidence of

aggressive driving.

•Increased congestion on roadways;

•Running late, too many obligations;

•Anonymity provided by a closed vehicle;

•Disregard for others and the law;

• Chronic or pathological anger;

•Traffic jams caused by construction zones with little or no work going on;

•Fewer mental health services available than in the past;

•Violent video games;

• Violent films and television programs;

•Increased levels of intrapersonal and interpersonal stress, including stress associated

with employment, two-career families, familial relationships, child-care issues, eldercare issues, and fundamental economic and technological changes in society;

•Loud, thumping music on the car radio while driving;

•The need to “save face” and overcome feelings of being disrespected by another

driver;

•The need to assert one’s identity and maintain control in a situation where one fears

losing control;

•A cultural focus on “time” as a limited resource, including concerns about “saving

time,” “using time wisely,” “being on time,” and “time is money”;

•A human need for “space” that causes some drivers to be territorial about

infringements on their space;

• The summer heat;

•Popular culture’s focus on machismo and masculinity;

•Increased immigration trends leading to a mixture of different driving styles;

•A widespread increase in interpersonal violence, including murder, domestic abuse,

and street crime;

•A focus on individualism that produces a “me first” mentality;

•Oppressive social conditions that produce feelings of alienation in individuals;

•Slow drivers (especially in the “fast lane”);
– 40 –

•Defensive driving habits that produce an inflated concern about the poor driving skills

of others;

•A lower emotional intelligence and moral character than exhibited in past societies;

•An innate human drive to aggression;

•Decreased drivers education in schools;

•Reduced levels of traffic enforcement;

•Ignorance about the “rules of the road”;

•Dehumanization of the other;

•An attempt to attain power in an otherwise powerless existence;

•Increased commuting distances and durations;

•Fewer people relying on mass transit and more relying on cars;

•An increased sense of invincibility behind the wheel of a 3,000-pound vehicle;

•A cultural propensity to promote and reward competitive, tenacious, and aggressive

behavior; and,

•An individual propensity to perceive one’s vehicle as an extension of oneself.
– 41 –

APPENDIX B

DATA TABLES AND FIGURES
– 42 –
– 43 –

Comparison Site 1: W. Washington St.

0

1

2

3

4

5

6

7

8

9

10

March April May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001

Comparison Site 2: E. Raymond St.

0

2

4

6

8

10

12

14

16

18

March April May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001

Marion County Comparison Zone Crash Figures.

TABLE B-1

PROPERTY DAMAGE ONLY (PDO) CRASHES DURING THE PROGRAM PERIOD

AND THE SAME SIX-MONTH PERIOD ONE YEAR EARLIER:

MARION COUNTY SPECIAL ENFORCEMENT ZONES AND COMPARISON ZONES

Enforcement Zone Comparison Period Program Period Change

B 63 106 +68%

C 69 70 +1

D 46 72 +57 %

Total 178 248 +39%

Comparison Zone Comparison Period Program Period Change

1 30 31 +3%

2 53 72 +36

3 94 135 +44 %

Total 177 238 +34%

TABLE B-2

INJURY CRASHES DURING THE PROGRAM PERIOD AND THE SAME SIX-MONTH PERIOD

ONE YEAR EARLIER: MARION COUNTY SPECIAL ENFORCEMENT ZONES AND COMPARISON ZONES

Enforcement Zone Comparison Period Program Period Change

B 25 42 +68%

C 24 24 0%

D 32 29 -9 %

Total 81 95 +17%

Comparison Zone Comparison Period Program Period Change

1 10 15 +50%

2 30 31 +3

3 63 63 0 %

Total 103 109 +7%

Comparison Site 3: E. 38th St.

0

5

10

15

20

25

30

35

March April May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug.

PDO Crashes Injury Crashes

Comparison Period Program Period

2000 2001
– 44 –

TABLE B-3

TARGET PCFS DURING THE PROGRAM PERIOD AND THE SAME SIX-MONTH PERIOD

ONE YEAR EARLIER: MARION COUNTY SPECIAL ENFORCEMENT ZONES AND COMPARISON ZONES

Enforcement Zone Comparison Period Program Period Change

B 57 103 +81%

C 54 59 +9

D 49 64 +31 %

Total 160 226 +41%

Comparison Zone Comparison Period Program Period Change

1 30 28 -7%

2 67 77 +15%

3 99 133 +34 %

Total 196 238 +21%

TABLE B-4

PROPERTY DAMAGE ONLY (PDO) CRASHES DURING THE PROGRAM PERIOD

AND THE SAME SIX-MONTH PERIOD ONE YEAR EARLIER:

TUCSON SPECIAL ENFORCEMENT ZONES AND COMPARISON ZONES

Enforcement Zone Comparison Period Program Period Change

1 31 33 +7%

2 20 24 +20

3 11 14 +27

4 22 30 +36 %

Total 84 101 +20%

Comparison Zone Comparison Period Program Period Change

1 30 18 -40%

2 11 25 +127%

3 18 26 +44%

4 27 23 -15 %

Total 86 92 +7%

TABLE B-5

INJURY CRASHES DURING THE PROGRAM PERIOD AND THE SAME SIX-MONTH PERIOD

ONE YEAR EARLIER: TUCSON SPECIAL ENFORCEMENT ZONES AND COMPARISON ZONES

Enforcement Zone Comparison Period Program Period Change

1 21 18 -14%

2 8 9 +13%

3 8 9 +13

4 24 23 -4 %

Total 61 59 -3%

Comparison Zone Comparison Period Program Period Change

1 16 13 -19%

2 13 11 -15%

3 11 16 +45%

4 22 13 -41 %

Total 62 53 -15%
– 45 –

TABLE B-6

TARGET PCFS DURING THE PROGRAM PERIOD AND THE SAME SIX-MONTH PERIOD

ONE YEAR EARLIER:TUCSON SPECIAL ENFORCEMENT ZONES AND COMPARISON ZONES

Enforcement Zone Comparison Period Program Period Change

1 45 37 -18%

2 24 27 +13%

3 18 20 +11%

4 34 38 +12 %

Total 121 122 +1%

Comparison Zone Comparison Period Program Period Change

1 33 22 -33%

2 19 23 +21%

3 20 29 +45%

4 32 24 -25 %

Total 104 98 -6%
– 46 –
DOT HS 809 707

March 2004