The Police Chief, the Professional Voice of Law Enforcement
Advanced Search
September 2016HomeSite MapContact UsFAQsSubscribe/Renew/UpdateIACP

Current Issue
Search Archives
Web-Only Articles
About Police Chief
Law Enforcement Jobs
buyers Your Oppinion

Back to Archives | Back to July 2010 Contents 

Automated Speed Enforcement on Arizona State Highways: A Second Look

By Jack Hegarty, Lieutenant Colonel, Arizona Department of Public Safety, Highway Patrol Division

Click to view the digital edition.

n automated speed enforcement demonstration project on a freeway, likely the first of its kind, was completed by the city of Scottsdale, Arizona, and the Arizona Department of Transportation (AZDOT) in 2006. A 2007 Police Chief article provided an early assessment of the effectiveness and results of the project.1 In the time since that article was published, the final report on the project has been made available, and automated speed enforcement has been significantly expanded in Arizona. 2 Another examination of the impact of the 2006 demonstration project and an initial assessment of the expanded program in Arizona can now be performed.

Both programs are unique in their scope and application and should provide valuable insight for other states considering automated speed enforcement on state roads and highways. The demonstration project on State Route 101 (SR101) in the city of Scottsdale occurred from February to October 2006. The system was turned over to the Arizona Department of Public Safety (AZDPS) after 2006, but it was then deactivated and removed due to construction on that section of freeway. This provides an opportunity to assess crash data in the period before, during, and after the project. The construction involved adding a high-occupancy lane to the existing three lanes of traffic in each direction.

Table 1 includes total crashes in the automated speed enforcement zone from 2005 to 2009 during the program year dates, January 22 to October 23. Each year in the table includes crashes from this period only so they can be compared to the 2006 program year. While the system had been turned off and later removed after 2006, the new program included mobile photo speed enforcement and those units occasionally were stationed in the 2006 program area in the following years. This eliminated the ideal before and after analysis conditions, but the data are interesting regardless. The contributing factors listed are not mutually exclusive and therefore do not add to the total crashes. “Speed” in this table includes any failure to control violations, which normally are vehicles that were not exceeding the posted limit yet were responsible for crashes.

Table 1: SR101 ASE Program Area Contributing Causes (2006 is the Program Year)
Total Crashes209185173174156
Exceed Posted Limit32110
Source: Arizona DPS Crash Data
*Includes failure-to-control violations

While overall crashes decreased significantly in 2006—11.5 percent compared to 2005—crashes continued to decrease after the program year. The decrease in 2007 was 6.5 percent; in 2009, it was 10.3 percent (see figure 1). This suggests other factors besides photo enforcement may have influenced crashes during the period 2005 to 2009 (see figure 2). The overall trend from 2005 to 2009 is not significantly different from national or regional trends that display similar crash reductions, and these do not involve any comprehensive or statistically significant automated enforcement programs.

The final study by Simon Washington, Ph.D., et al. regarding this project clearly shows decreases in speeds at the measurement sites and reductions in certain types of crashes during certain times of day.3 However, the assumption utilized in the analysis that traffic volume is proportional to traffic crashes is not widely accepted by traffic safety experts.4 Traffic volumes and crash rates are clearly related but not necessarily linearly or similarly over varying roadway types. The assumptions and the narrow focus of analysis regarding time of day and types of crashes minimize the lessons learned from the program and the final study. Clearly, the national trends in fatal crash reductions that are similar to the overall crash reductions in the Washington study on the SR101 program are not due to automated enforcement; other factors are likely significant. Experts at the National Highway Traffic Safety Administration (NHTSA) and other organizations indicate that vehicle safety systems are more advanced and widespread than at any other point in passenger vehicle history. 5 Vehicles on the road with dual front air bags surpassed 90 percent for the first time in 2007, and that number continues to increase. This is not a data set utilized in most research, but it is certainly a factor in the fatal crash reductions experienced nationwide since 2006.


Since the 2006 test program on SR101, Arizona has implemented a statewide speed photo enforcement system with both fixed sites and mobile photo enforcement vehicles. Beginning October 1, 2008, 36 fixed sites on freeways and interstates in the greater Phoenix area were in operation, as well as 40 mobile units statewide.6 This system was planned and implemented after the 2008 Arizona legislative session required AZDPS to enter into a contract for automated speed enforcement on state highways.

The fixed units utilized sensors in the roadway to measure vehicle speeds, and the mobile units used conventional radar technology. All the utilized speed measurement and photographic technology were tested to extremes by Arizona weather, road, and traffic conditions, and the roadway environment. The freeways in the Phoenix area are multilane, and significant issues were encountered regarding sun glare, camera flash color and intensity, and blockage of violators by other vehicles. Some neighborhood residents in areas in proximity to the photo enforcement equipment complained of camera flashes at night. Darker, red lenses seemed to solve this problem. All of these issues made early expectations regarding driver identification rates and successful service of violation notices overly optimistic and the lessons learned are significant. Only 53 percent of speed activations resulted in a violation notice being issued in the first year of the program and some drivers simply ignored the notices and resulting citations.7 These are significant issues for states and communities considering comprehensive automated speed enforcement programs.

The service of violations is a critical component of any program and must be viable for program success. NHTSA guidelines emphasize public outreach to educate motorists and communicate with the courts and other stakeholders to obtain support for photo enforcement prior to implementation.8 The AZDPS system required a full year of experience after implementation to reach a point at which the administrative support process was complete and effective. Activations were processed by the AZDPS and its vendor as notices of violations and then passed onto the court system as citations when the notices were not satisfied. Significant efforts and partnerships with courts to facilitate the service of citations were required to reach a point where stakeholders at all levels understood and committed to a system that effectively processed violations. Significant investments were made by the AZDPS and its vendor to reach this level of effectiveness. Anticipated revenues for the state and the vendor did not materialize in the first year of the program. By mid-2010, after approximately 18 months of full-scale operations, activations and successful processing of violation notices and citations had stabilized and costs and revenues had become clearer.9

There has been significant debate around the country regarding crash reduction and photo enforcement, and Arizona’s programs have been no exception. In Arizona, as in the rest of the country, fatal crashes decreased significantly in 2008 and 2009. Because the statewide photo enforcement went into effect October 1, 2008, the reductions in Arizona occurred during the same time frame as the national reductions in fatal crashes, so the impact of photo enforcement is unclear.

The analysis of the safety impact of automated speed enforcement is complex and controversial. Highways, roads, and streets are not laboratories, and conditions cannot be easily controlled. Traditional before-and-after comparisons or designation of a control corridor as a comparison is problematic due to constantly changing traffic and road conditions. Multiple factors impact traffic crashes, including vehicle safety systems, engineering changes, road conditions, construction of alternate routes, and traffic volumes. None of these factors can be controlled or held constant for analysis of the impact of automated enforcement. Multivariate regression analysis could produce significant conclusions if accurate data were available. Unfortunately, accurate and sufficiently large data sets regarding traffic volumes, road conditions, vehicle safety systems, driver profiles, and so on, are not available, so this type of analysis is not practical and, if applied, could yield misleading results.

Compounding the controversy, governments and traffic safety organizations quote NHTSA research indicating that a significant percentage of fatal crashes—usually around 30 percent—are caused by speed.10 This statement is part of the justification for automated speed enforcement; however, collection methodology in the states can vary from the NHSTA methodology, resulting in misinterpretation of the data. Most states, including Arizona, allow investigators to select from a multitude of crash causations when documenting crashes, and NHTSA then compiles these data. The process results in state-reported crashes caused by excessive speed, speed too fast for conditions, failure to control a vehicle to avoid a collision, and similar speed-related violations, to all be recorded as speed-related in the NHTSA Fatality Analysis Reporting System (FARS) database. On state highways in Arizona, excessive speed or traveling above the speed limit was listed as the primary cause in only 2 percent of fatal crashes in 2009. In contrast, inattention or distracted driving was recorded as the contributing cause in 19 percent of all fatal crashes on state highways last year, and impaired drivers were responsible for 15 percent.11

Photo enforcement opponents point to the fact that fatal traffic crashes have been decreasing for several years nationally. NHTSA, which maintains fatal traffic crash data and assesses trends, reports significant reductions in fatal traffic crashes, including a 9 percent decrease nationwide in 2008. Early estimates of 2009 data indicate another significant decrease: The first six months of 2009 resulted in a 7 percent reduction in fatal crashes, compared with the first six months of 2008. Initial 2009 estimates indicate an 8.9 percent decrease for the year. Traffic volumes were down nationwide as well.

According to traffic crash records maintained by AZDPS and AZDOT, fatal crashes in 2008 decreased 12 percent statewide and 11.5 percent on state highways. On Phoenix’s freeways, AZDPS records indicate a decrease of 31 percent in fatal crashes in 2008 and another 5 percent reduction in 2009.12 This compares with a 20 percent decrease in fatal crashes statewide on highways in 2009. Total crash damages—fatal, injury, and property combined—decreased 17 percent in 2008 and another 17 percent in 2009 on Phoenix area freeways. These decreases compare with national decreases in fatal crashes of 9 percent in 2008 and 8.9 percent in 2009.

Several factors are involved with these decreases. Statewide, roadways experienced some engineering improvements. However, in the Phoenix area, significant projects were completed in 2008 and 2009, and these improvements likely played a significant role in traffic volume reductions and crash decreases. Still, a 31 percent decrease in fatal crashes in 2008 on Phoenix freeways is fairly incredible and unprecedented. Statistically, however, caution should be exercised as the total for Phoenix freeway fatal crashes in 2007 was 86; in 2008, it was 59. While a significant decrease, these totals are small numerically, and their use statistically may be limited. The total decrease is small enough that minor engineering changes or traffic volume differences, as opposed to photo enforcement, could account for the entire decrease due to the small data sets. Therefore, caution should be exercised in assessing this change. Photo enforcement was implemented only during the last quarter of 2008 and clearly is not responsible for the bulk of the 31 percent decrease. Total crashes in the Phoenix area, which numerically are much more useful, decreased 17 percent in 2008.

How does the AZDPS statewide photo enforcement system impact the national discussion of photo enforcement programs? The full implementation of the AZDPS automated speed enforcement system occurred on October 1, 2008, and impacted only the last quarter of 2008. Table 2 indicates that the reductions in Phoenix-area fatal crashes in the first full year of photo enforcement implementation are similar to the national trends and actually have not kept pace when fatal crashes are compared. In the first nine months of 2008, prior to the full implementation of photo enforcement on freeways, fatal crashes on Arizona’s Valley Freeway System were down 11 percent compared to the first nine months of 2007 and 30 percent compared to the first nine months of 2006. None of these periods was significantly influenced by photo enforcement. Nationally in 2009, fatal crashes were down 8.9 percent. On Phoenix area freeways, fatal crashes were down 5 percent. This is significant since 2009 was the first full year of automated speed enforcement in the Phoenix area. The fact that the area most impacted by photo enforcement did not keep pace with national fatal crash decreases or Arizona state trends is troubling and invites further analysis.

Table 2: Crashes on Phoenix Area Freeways Compared to U.S. Fatal Crash Totals
Phoenix Fatal Crashes99865956
Percent Change5%-13%-31%-5%
All Phoenix Crashes22,29321,45217,73514,807
Percent Change4%-4%-17%-17%
Arizona Highway Fatal Crashes398321284228
Percent Change3%-18.3%-11.5%-20%
U.S. Fatal Crashes38,64837,43534,01730,990
Percent Change-15%-3%-9%-8.9%
Source: DPS Personnel Deployment Program database and NHTSA FARS

The vertical lines in figure 3 indicate the start date of the statewide-automated speed enforcement program in Arizona. Clearly, significant decreases in fatal crashes occurred after its implementation. It is interesting, however, that the Phoenix area saw the smallest decrease while enjoying the largest implementation of photo enforcement. More than 90 percent of all statewide photo enforcement violations occurred in Maricopa County, which includes Phoenix, yet the decrease in fatal crashes was 5 percent. Nationally, fatal crashes were down 8.9 percent; statewide, they decreased 20 percent.

While Arizona experienced a significant decline in fatal crashes from 2006 to 2008, a portion of which proponents attribute to photo enforcement, other states—none of which has comprehensive automated speed enforcement systems on state roads—experienced similar declines. New Mexico saw a 24 percent decline, California a 19 percent drop, and Nevada a 25 percent reduction. The Arizona reduction from 2006 to 2008 was 24 percent (see table 3).13

Table 3: Fatal Crash Change 2006 to 2008
New Mexico-24%
Source: DPS Personnel Deployment Program database and NHTSA FARS

When specific segments of freeway in the Phoenix area are analyzed, the impact of photo enforcement is not clear. Figure 4 depicts total traffic crashes for four Phoenix area freeway segments, two of which had a significant fixed photo speed enforcement presence. All segments on Phoenix freeways had some level of mobile speed enforcement, so the comparisons are not between segments that have significant photo enforcement versus zero photo enforcement. The segments with fixed sites had significantly more photo enforcement influence than highways with mobile speed enforcement. The arrows in the year 2008 indicate the implementation of the statewide photo enforcement system.

Other Factors

What other factors are significant to crashes? AZDOT has added several hundred lane miles to Phoenix freeways in recent years. The State Route 202 loop was 100 percent completed in July 2008, just prior to the full implementation of the AZDPS photo enforcement system, adding a new option for east valley commuters and reducing traffic volumes on other major corridors. Other freeways also had significant construction projects completed in the last three years that resulted in hundreds of additional lane miles, and traffic volumes are down approximately 6 percent from 2006 to 2008 on Phoenix valley freeways.14 All of these factors could have impacted the historic crash decreases experienced in 2008 on Phoenix freeways.

This traffic volume decrease is significant, since minor changes in traffic volume and freeway lane mileage can significantly impact crash rates. NHTSA research has historically demonstrated a direct connection between traffic volumes and crashes. As volumes increase, crash rates increase and as volumes decrease, crashes diminish. The relationship is not linear, however, and cannot be utilized to predict crash rates. Small changes in volumes can have significant impacts on crashes. Additionally, freeway crash rates are largely dependent on secondary crash frequency. Secondary crashes occur when a crash blocks the roadway and the resulting congestion causes additional crashes. The effect makes the relationship between traffic volumes on major freeways and crashes much different than on rural roads or surface streets. The difference is likely significant. An excerpt from a NHTSA report describes the difficulty in relating crash rate to traffic volumes.

… 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.15


So where does all this information lead us regarding automated speed enforcement in Arizona? Any conclusion drawn based on raw crash data or anecdotal observations during the periods before and after the implementation of the AZDPS automated speed enforcement system that does not take into account all the potential factors that impact traffic crashes is not scientific and should not be utilized when deciding the fate of automated speed enforcement on state highways. Internationally recognized research universities and organizations have never conclusively proven automated enforcement as an effective, long-term crash reduction tool, except in the immediate area of the automated enforcement device.16 In addition, it appears the area with the most significant photo enforcement presence—Phoenix freeways—lagged the national trend in fatal crash reduction in its first full year of implementation.

The debate will likely continue. A straightforward and accurate discussion of the impact of automated speed enforcement and the due process concerns created by its operation will assist public safety leaders, elected officials, and, potentially, voters to decide its fate. AZDPS will watch the unfolding debate regarding the highway photo enforcement program with interest, but its focus will continue to be on improving safety on the state’s highways with conventional traffic enforcement and programs. Several new programs have been implemented recently such as Operation Safe Commute, Operation Safe Driver, and the DUI Fugitive Warrant program. AZDPS traditional enforcement programs targeting occupant restraint and impaired drivers will continue with renewed emphasis. These programs will continue to be the mainstay of fatal crash reduction efforts on Arizona highways and automated enforcement will require further analysis to properly gauge its worth and effectiveness. ■


1Jack Hegarty, “Automated Speed Enforcement Study,” The Police Chief 74 (July 2007): 28-31, (accessed May 18, 2010).
2Jack Stuster, “Implications,” Aggressive Driving Enforcement: Evaluations of Two Demonstration Programs, National Highway Traffic Safety Administration, DOT HS 809 707 (March 2004), (accessed May 18, 2010).
4Simon Washington et al., Evaluation of the City of Scottsdale Loop 101 Photo Enforcement Demonstration Program, Final Report AZ-684, Arizona Department of Transportation (November 2007), (accessed May 18, 2010).
5“2007 Motor Vehicle Occupant Safety Survey (MVOSS) Finds Continued Strong Support for Air Bags,” Traffic Safety Facts: Traffic Tech, March 2009, (accessed May 18, 2010).
6“Photo Enforcement Freeway Camera Locations & Map,” Arizona Department of Public Safety, (accessed May 18, 2010).
7State of Arizona Office of the Auditor General, Department of Public safety—Photo Enforcement Program, no. 10-02 (January 2010), (accessed May 18, 2010).
8U.S. Department of Transportation, Federal Highway Administration, Speed Enforcement Camera Systems Operational Guidelines, DOT HS 810 916 (March 2008),
10NHTSA’s National Center for Statistics and Analysis, “Speeding,” Traffic Safety Facts: 2008 Data, DOT HS 811 166, November 2009,
11Arizona Department of Public Safety Traffic Crash and Personnel Deployment internal database report, retrieved February 1, 2010; NHTSA’s National Center for Statistics and Analysis, “Early Estimate of Motor Vehicle Traffic Fatalities for the First Half (January-June) of 2009,” Traffic Safety Facts, DOT HS 811 207 (October 2009),; and NHTSA’s National Center for Statistics and Analysis, “Early Estimate of Motor Vehicle Traffic Fatalities in 2009,” Traffic Safety Facts, DOT HS 811 291 (March 2010), (all accessed May 18, 2010).
12Arizona Department of Public Safety Traffic Crash and Personnel Deployment internal database report, retrieved February 1, 2010.
13“Data Resource Website,” National Highway Traffic Safety Administration, (accessed May 18, 2010).
14Multimodal Planning Division, “Average Annual Daily Traffic (AADT),” Arizona Department of Transportation, (May 18, 2010).
15Simon Washington et al., Evaluation of the City of Scottsdale Loop 101 Photo Enforcement Demonstration Program, Final Report AZ-684, Arizona Department of Transportation (November 2007), (accessed May 18, 2010).
16Jack Stuster, “Implications,” Aggressive Driving Enforcement: Evaluations of Two Demonstration Programs, National Highway Traffic Safety Administration, DOT HS 809 707 (March 2004),; Lawrence E. Decina, Libby Thomas, Raghavan Srinivasan, and Loren Staplin, Automated Enforcement: A Compendium of Worldwide Evaluations of Results, September 2007, DOT HS 810 763, (accessed May 18, 2010).

Please cite as:

Jack Hegarty, "Automated Speed Enforcement on Arizona State Highways: A Second Look," The Police Chief 77 (July 2010): 46–52, (insert access date).



From The Police Chief, vol. LXXVII, no. 7, July 2010. Copyright held by the International Association of Chiefs of Police, 515 North Washington Street, Alexandria, VA 22314 USA.

The official publication of the International Association of Chiefs of Police.
The online version of the Police Chief Magazine is possible through a grant from the IACP Foundation. To learn more about the IACP Foundation, click here.

All contents Copyright © 2003 - International Association of Chiefs of Police. All Rights Reserved.
Copyright and Trademark Notice | Member and Non-Member Supplied Information | Links Policy

44 Canal Center Plaza, Suite 200, Alexandria, VA USA 22314 phone: 703.836.6767 or 1.800.THE IACP fax: 703.836.4543

Created by Matrix Group International, Inc.®