Traffic Tech #96: Field Test of Combined Speed, Alcohol, and Safety Belt Enforcement Strategies |
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Number 96 June 1995
FIELD TEST OF COMBINED SPEED, ALCOHOL, AND SAFETY BELT ENFORCEMENT STRATEGIES
The National Highway Traffic Safety Administration (NHTSA) sponsored a study to determine the potential effectiveness of a combined enforcement program that focused on speed, alcohol, and safety belts. Combined enforcement programs concentrate on several problem behaviors at a time. It is thought that if motorists perceive a heightened risk of arrest for each type of violation, this will lead to greater deterrence and enforcement efficiency.
Lexington, Kentucky, Wichita, Kansas, and Knoxville, Tennessee implemented well-publicized combined enforcement programs. Each program emphasized five different enforcement strategies in sequence during a period of about one year. Examples included saturation patrols in high crash locations, sobriety checkpoints, youth campaigns, and special Driving While Intoxicated (DWI), and speed enforcement squads. For each strategy, publicity programs included press conferences, billboard advertising, public service announcements on TV and radio, and presentations to community groups. A general theme stressed simultaneous enforcement of speed, DWI, and safety belt laws in each program. Each of these combined programs was in continuous operation during the test period, unlike periodic blitzes, which are brief periods of high intensity publicity followed by a short but intensive enforcement program such as saturation patrols.
Mid-America Research Institute conducted an evaluation to measure the effect of the combined programs on:
Measurements were made in the test sites before, during, and after the combined programs, and in closely matched control sites that did not implement any special enforcement activity.
Lexington
In Lexington, the combined program maintained a high level of publicity and enforcement activity directed at all three target behaviors throughout the test period. There was a reduction of about 10 percent in surrogate measures of alcohol-related crashes such as nighttime single vehicle crashes, and a 12 percent reduction in the number of vehicles exceeding the speed limit by at least 5 mph. Minor injury crashes declined by about 17 percent during the test period, a possible reflection of the lower speeds. Safety belt usage in Lexington remained at its already high rate throughout the test period.
Wichita
In Wichita, the combined enforcement program significantly increased enforcement activity directed at DWI. Enforcement activity for the other two target violations either decreased or increased only moderately. The phasing of the comprehensive publicity campaign did not always coincide with the phasing of the various combined enforcement strategies. This approach only partially met the basic requirements of a combined enforcement program. The effort against DWI did meet most of the requirements of the project, and resulted in reductions in nighttime crashes of at least 20percent. This measure is often used as a proxy of alcohol-related crashes.
Knoxville
The Knoxville combined program had no measurable effect on any of the evaluation parameters. The program was unable to maintain increased enforcement activity throughout the test period as measured by the number of citations issued and number of officers assigned to enforce the target violations. Furthermore, the publicity campaign focused on the multiple threat aspect of the combined program rather than on individual enforcement strategies. As a result, partial implementation of the combined enforcement program may not have been sufficient to convince the driving public that enforcement activity had changed or that their risk of detection had increased.
Comparisons were also made between two of the test programs and a program in a similar test site where a speed enforcement program alone was implemented. The single issue program had a greater impact on speed related violations than either of the combined programs.
These findings imply that continuously operating combined enforcement programs need to maintain a high level of increased enforcement activity and publicity. Since two of the test sites could not consistently maintain this increased activity, it appears that a combined enforcement program may be difficult to implement for many communities. This type of program clearly places a strain on police resources because of the need to simultan-eously increase enforcement for all target behaviors.
These findings also imply that a single emphasis enforcement approach can have a greater impact than a combined approach. This effect is achieved, however, without the positive effect on other behaviors that the combined program can achieve. A combined enforcement program might have a greater overall highway safety impact than a single emphasis program of comparable magnitude.
All the test sites had secondary safety belt enforce-ment laws for adults. Secondary enforcement means that an officer can issue a safety belt citation only if the vehicle has been stopped for some other reason. It is possible that the combined enforce-ment programs would have shown stronger results had the sites been able to practice primary enforcement.
Limited copies of Field Test of Combined Speed, Alcohol, and Safety Belt Enforcement Strategies, are available from the Office of Program Development and Evaluation, NHTSA, NTS-32, 400 Seventh Street, S.W., Washington, DC 20590, (202) 366-2752, or send a fax to (202) 366-7096. In addition to the Summary Report, limited copies of the individual site reports for Lexington, Wichita, or Knoxville are also available. Please specify the reports you would like.
U.S. Department of Transportation
National Highway
Traffic Safety
Administration
400 Seventh Street, S.W. NTS-33
Washington, DC 20590
Traffic Tech is a publication to disseminate information about traffic safety programs, including evaluations, innovative programs, and new publications. Feel free to copy it as you wish.
If you would like to receive a copy contact:
Linda Cosgrove, Ph.D., Editor,
Evaluation Staff Traffic Safety Programs
(202) 366-2759