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Mid-America Research Institute, PO Box 3329, Shepherdstown, WV 25443, USA
Checkpoints or roadblocks have long been accepted as an effective impaired driving enforcement method in the United States. However, until recently, they have been implemented primarily on a local level and intermittently. In late 1993 and early 1994, respectively, New Mexico and Tennessee initiated year long, statewide checkpoint programs. One state's program features checkpoint blitzes on alternate months and the other involves a lower level of intensity of checkpoints but on a continuous basis. This paper reports on the results of each program in terms of effect on crashes and public awareness and perceptions of impaired driving enforcement. A discussion of the differences between the effects of the two approaches is also included.
Checkpoints or roadblocks have long been known to be an effective impaired driving enforcement method in the United States, especially in terms of achieving general deterrence (Lacey et al., 1986). However, until recently, checkpoints have generally been implemented in the US on a local level and intermittently (Ross, 1992). This purportedly has led to a diminished effectiveness of this countermeasure approach in achieving a long term deterrent effect on impaired driving. Recently two of the United Sates have implemented yearlong statewide programs of impaired driving checkpoints thus affording an opportunity to assess the viability and effectiveness of this enforcement strategy for larger jurisdictions in the United States. Additionally, the two states differ in their implementation approach in that one is conducting intensive checkpoint blitzes during alternate months while the other has chosen to implement checkpoints more continuously, but at a lower level of intensity. This offers the opportunity to assess whether one approach is preferable over the other. The two states under study are New Mexico, in the southwest of the United States, and Tennessee, in the southeast. Neither study is complete and thus only preliminary results are presented here. Results reported here focus on potential effects on fatal crashes and public perceptions.
New Mexico initiated their checkpoint program, "Operation DWI," in December 1993. Their program involves the conduct of well publicized checkpoint blitzes in alternate months. A complicating factor is that several legislative changes related to driving while intoxicated (DWI) were implemented in January 1994. Grants were given to enforcement agencies in all of the larger local jurisdictions throughout the state and to the Highway Patrol by the New Mexico Traffic Safety Bureau to purchase equipment and fund overtime enforcement personnel to assist in implementing the checkpoints. Equipment included items such as generators, lights, cones, special signs, traffic counters and trailers to transport the equipment. Each jurisdiction developed policies and submitted plans as to how they would carry out the checkpoints. The checkpoints were coordinated to ensure that intensive enforcement activity was carried out throughout each blitz month. At the state level the Traffic Safety Bureau coordinated publicity efforts to draw the public's attention to the enforcement efforts. These were supplemented by local efforts in this area.
A telephone survey of New Mexico residents was conducted in the Fall of 1993, the Spring of 1994 and the Fall of 1994. In each wave responses were sought from at least 600 individuals (400 male, 200 female).
One question asked was "In the past year when you were driving, how many times have you been stopped at a police checkpoint where they were looking for alcohol use or drunk driving?" On the first wave 18.7% of women responded that they had been stopped one or more times. On the two waves subsequent to initiation of the program 24% and 24.9% responded that they had been stopped one or more times. Thus there seems to be an increase in reported exposure of female drivers to checkpoints coincident with implementation of the program.
Male drivers, however started out with a higher level of exposure (34.3% at wave one, which essentially did not change (32.2% at wave 2 and 34.2% at wave 3). One candidate explanation for the somewhat different pattern between the two sexes is that perhaps women were asked to drive as designated drivers more frequently after initiation of the program.
Respondents were then asked if they thought the chances of a drunk driver being stopped had change in the past year and in what direction. At wave 1, 47.1% of women felt it had increased, 61.8% at wave 2 and 69.6% at wave 3. For men the corresponding figures were 60.1%, 57.9% and 69.6%. Thus both groups perceptions of increased enforcement have increased with that for women being more dramatic.
Another question asked was "In New Mexico, how likely do you think it is for a drunk driver to be stopped by a police officer?" In the first wave 24.1% of female respondents indicated that it was almost certain or very likely. That figure rose to 27.1% at the second wave and 33.9 at the third. For men the value was 24.4% for wave 1, 27.6 for wave 2 and 19.6 for wave 3. Thus the perceived risk of arrest for women seems to be gradually improving, while that of men is fluctuating.
Self reported drinking driving behavior was measured by asking "In the past year, about how many times have you driven within two hours after drinking any type of alcohol, even as much as one drink?" More men than women would admit to this behavior but there was little change in either group over time. At wave 1, 21% of women admitted to having done so, 17.5% at wave 2 and 19.9% at wave 3. For men those figures were 36.9%, 38.1% and 41.4%.
On the third wave of the survey a question asking respondents whether they had heard of a program called "Operation DWI" was added to the instrument. Sixty-seven point seven percent of women reported they had compared to 60.4% of men.
In general, there was little movement on any of the survey measures of perception of risk, sanction certainty or reported drinking driving behavior. However, for most measures what little movement there was was in the desired direction.
An analysis of fatal crashes for the period 1988 through the first nine months of 1994 involved an interrupted time-series approach employing a shock variable designed to simulate the introduction of the Operation DWI intervention with a value of 1 during the months of checkpoint operations and a value of 0 during all other months. A log-transformed seasonal model gave the best fit to alcohol-related fatal crashes.
For the months in which the intervention was active, alcohol related fatal crashes were reduced by 3.7 per month or about 21% (t=-1.6). This analysis, while suggestive of program effect during checkpoint months, must be regarded as preliminary and will be refined when a more extensive data series becomes available and will be supplemented by comparison series from adjoining states.
In March 1994, Tennessee initiated a statewide impaired driving checkpoint program labeled "Checkpoint Tennessee." With equipment purchases funded by the US National Highway Traffic Safety Administration, but personnel provided through diversion of existing resources to this activity, four sets of three checkpoints are conducted throughout the state every weekend using specially equipped vans with generator, lights, cones, signs, video taping and evidential breath testing equipment. Passive alcohol sensors in flashlights are also used to assist the officers in detecting impaired drivers. Periodically checkpoints are scheduled on the same night in each of the 95 counties in the state. These, necessarily, do not involve as many officers and as much equipment per checkpoint as those previously described. The checkpoints are coordinated and conducted primarily by the Tennessee Highway Patrol with support from local law enforcement agencies. Publicity in support of the program was stimulated by obtaining the special cooperation of a single television station in each of the four major markets in the state. They each took on Checkpoint Tennessee as a special project. This publicity was enhanced by hard news coverage from other outlets, a statewide billboard campaign and press releases announcing individual checkpoints, followed up by reports of their results.
Two waves of a paper and pencil survey have been administered in Driver's License offices in support of the Checkpoint Tennessee evaluation activities. The first wave of the survey was administered in March 1994 prior to the formal announcement and initiation of the Checkpoint Tennessee program, a second wave was administered during the summer of 1994 beginning four months after program initiation Wave 1 yielded 1305 respondents and wave 2, 1071.
An open ended question was asked about exposure to drinking and driving programs. There were 205 responses for wave 1 and 134 for wave 2. The salient response change is that only one person mentioned roadblocks at wave 1 while 24 did at wave 2.
One question was intended to measure perceived risk of arrest and was phrased as follows, "Suppose you drive after drinking enough to violate Tennessee's drinking and driving law. What are you chances of being arrested by the police?" At wave 1, 47% of respondents thought that the risk of arrest was 60% or greater, by wave 2 that value had eroded somewhat to 43.5%.
Respondents were also asked, "How often do you drink alcoholic beverages and then drive within a couple of hours?" The percentage of persons admitting to this behavior dropped slightly between waves with 17.4% admitting to the behavior at wave 1 and 15.6% at wave 2. They were then asked about impaired driving with the question, "Within the last 3 months, how often do you think you may have driven after drinking too much?" At wave 1, 8.6% of respondents admitted to this behavior and at wave 2, 7.3% - a slight improvement. There was virtually no change in the pattern of responses to the question asking whether their drinking driving behavior had changed compared with three months ago.
There was also virtually no change in the percentage of respondent reporting having been stopped by a police officer at night. However, when asked if they had recently been through a checkpoint 7.9% said yes at wave 1 with 10.5% indicating so after initiation of the program. At both waves the public overwhelmingly supported the use of checkpoints rising from 88.1% at wave 1 to 91.6% at wave 2.
A preliminary time-series analysis of nighttime single-vehicle fatal (NSVF) crashes from January 1990 through October 1994 was conducted with a step-function intervention variable introduced coincident with the startup of the checkpoint program (April 1994). This revealed a reduction of 1.8 NSVF's per month, or about 8% (t=-1.02). Though this is suggestive of a program effect, additional data, both before and after the intervention, will be introduced into the final analysis to assess whether the effect reaches statistical significance.
The salient finding of this preliminary examination of two statewide sobriety checkpoint programs in the United States is that viable, continuing programs of this size can be implemented. Both states are continuing the programs into a second year. In the case of New Mexico, funding for this continuation is being provided by the Traffic Safety Bureau. In Tennessee, the Tennessee Highway Patrol is continuing the program without additional outside funding by diverting existing personnel resources to the program.
Since New Mexico also implemented extensive legislative changes coincident with the checkpoint program beginning, it is difficult to assess the relative merits of the two approaches to mounting checkpoint programs in terms of deterrence. With an extended series and control states more insight may be brought to that issue, however it is safe to say that statewide checkpoint programs are a viable approach to increasing deterrence of impaired driving and reducing the subsequent consequences.
Lacey, JH; Stewart, JR; Marchetti. LM; Popkin, C; and Murphy, PV. (1986). Enforcement and public information strategies for DWI (driving-while-intoxicated) general deterrence: Arrest drunk driving - The Clearwater and Largo, Florida experience. Chapel Hill, NC: University of North Carolina Highway Safety Research Center.
Ross, HL. (1992). The deterrent capability of sobriety checkpoints: Summary of the American literature. Washington, DC: US Department of Transportation, National Highway Traffic Safety Administration (DOT-HS 807-862).