A CONTROLLED EVALUATION OF THE DWI VISUAL DETECTION GUIDE TRAINING PROGRAMS FOR POLICE OFFICERS(1)

E. Vingilis, Ph.D.*, E. M. Adlaf, M.A.*,H. Blefgen, B.Sc.**, and C. Bennett, M.A.**

SYNOPSIS

The need and justification for specialized training of police officers in DWI detection is evident. Harris, Howlett, and Ridgeway recently developed an innovative DWI Detection Guide consisting of 23 driving cues capable of discriminating DWI from DWS. This study evaluated the DWI Detection Guide Training program versus informal class discussion on DWI and found no pre- versus post-arrest rate differences between the 2 programs but an overall main effect, with a significant post-DWI program increase in arrest rates. These results suggest that any program that focuses attention on DWI enforcement will increase arrest rates and that the Detection Guide is as effective with police officers as general discussion on DWI enforcement in increasing arrest rates.

INTRODUCTION

In North America, the detection rate by police officers of impaired drivers is low. North American statistics show that the average patrol officer makes only 1-5 impaireddriving arrests a year (N.H.T.S.A., 1980; Vingilis et al.1983). Estimates of apprehension risk for drinking driving range from a high of 1 in 200 (Beitel et al. 1975) to a low of 1 in 2,000 (Borkenstein, 1972; 1975). Lawson (1983),using roadside surveys of DWI driving surveys and DWI charges, has estimated that in Canada the risk ofapprehension is 1 in 514 impaired (blood alcoholconcentration, BAC, over 80 mg/100 ml or 80 mg%) trips, or 1 in every 2,575 impaired vehicle kilometers. Because thesubjective perception of apprehension of risk is strongly tied to objective probability, researchers concerned with developing effective countermeasure programs have recently begun to address the problem of detection rates (e.g. Bragg & Wilson, 1980; Harris et al. 1979; Nichols et al. 1981).

* Addiction Research Foundation, 33 Russell Street, Toronto, Ontario M5S 2S1, CANADA.

** The Barrie Police Force.(1) The views in this document are those of the authors

and do not necessarily reflect those of the Addiction Research Foundation.

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This absence of effective driving-while-impaired (DWI) detection is evident throughout the literature. Picton(1978), referring to a Transport Canada (1974) study conducted in Alberta, calculated that only 8% of drivers with BAC's greater than 80 mg% were detected by the police officers. These findings regarding the lack of detectability of individuals with high levels of alcohol by police officers was similarly confirmed by Pagano and Taylor(1979). They found that police officers were unable effectively to discriminate between subjects who had consumed either high or low levels of alcohol, even after personal interaction. Similarly, Beitel et al. (1975) indicated that the arrest rates tend to be extremely low, even if officers are highly motivated. Therefore, the inability of police officers on vehicle patrol accurately to detect DWI1s may be a significant explanatory factor in low detection and arrest rates.

Not only has the literature indicated the lack of training of police officers in the detection of DWI1s but, likewise, has supported the need and development of training programs. Arthur Young and Co. (1974) investigated factors which influenced DWI arrests and recommended periodic police officer retraining in DWI enforcement. That study also indicated that 47% of the police patrol officers felt that the specialized training improved their detection of DWI1s whereas only 35% felt that the training did not improve their detection ability.

IMPROVING DETECTION RATESThe need and justification for specialized training of

police officers in the detection of DWI1s is evident, yet only lately has work been done to develop training packages to improve detection rates. Harris et al. (1979) have recently developed a DWI detection guide to facilitate the application of research findings to the on-the-road detection of impaired driving by police patrol officers. The guide consists of 23 visual cues, a value for each cue reflecting the ability of the cue to discriminate between DWI and DWS (driving-while-sober) , and a set of 3 rules for estimating the probability for any set of observed cues. The 23 cues accounted for 92% of the cues observed during the detection study. A training package was developed consisting of a handbook, a film on the cues, and a DWI Detection Guide containing the visual cues and respective probability for each cue that a driver has a BAC equal to or greater than 100 mg% (see Harris et al. [1979] for details).

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Only one preliminary uncontrolled evaluation has been carried out by Harris et al. (1980) . The Guide was tested on a sample of 10 law enforcement agencies at locations throughout the United States. A statistically significant overall increase of 12% in the DWI arrest rate was found with the use of the Guide. (Rates during a 3-month period in which the Guide was used were compared to a 12-month baseline period.) Five of the police forces had significant increases of up to 94%, 4 forces had no change, and 1 force had a significant decrease. Although no statistically significant changes occurred in detection practices, such as those revealed by greater use of the more discriminating cues or by arrests of more drivers with lower BAC levels, trends were in the expected directions.

Unfortunately, major methodological problems with the research preclude definitive conclusions on the efficacy of the Detection Guide to increase the detection of DWI's. First and foremost, no control or comparison group was used in the evaluation. Thus, it is impossible to determine whether the Guide per se or other factors (such as, drinking driving becoming a police management priority) increased the arrest rate. Second, only a 3-month intervention period was evaluated. Little can be said about the efficacy of the program with so short a test period. Finally, the evaluation did not test for an improvement of the discriminability of police officers between DWI's and DWS's. The assumption of the program is that officers will make fewer false-positive and false-negative detections with the use of the Guide. This, however, was not evaluated.

The purpose of this investigation was to evaluate the effectiveness of the DWI Visual Detection Guide against an informal general class discussion on drinking-driving enforcement. Multiple evaluation measures were used to determine the usefulness of the training package.

METHODCommencing December 1, 1980, 0001 hours to November 1,

1981, 2400 hours, police officers from the southern Ontario City of Barrie (population 38,423) participated in a project to evaluate the effectiveness of the Harris et al. (1979) training package in comparison to an informal discussion on drinking-driving enforcement.

Because the small sample size did not allow for random assignment, the 26 participating officers were matched and ranked according to length of time on the force, age, and

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number of drinking-driving arrests made in 1980, and then assigned to 1 of 2 groups: the experimental group using the Harris package (n=13) or the control group involved in an informal discussion (n=13). The experimental group received the Harris DWI detection film, guide, cards, and instructions on their use. The control group received another drinking-driving film, guide, and cards that only contained a small list of vehicle (e.g. "going too fast or too slow," "turning too square corners") and driver (e.g. "speech slurred," "smell of alcoholic beverage") detection cues and a discussion of problems in drinking-driving enforcement.

The project ran for a period of 48 consecutive weeks, or 11 police reporting periods (28 days = 1 reportingperiod). Weeks 1-20 represented pre-intervention, Week 21 (April 20-26, 1981) was intervention, followed bypost-intervention, Weeks 22-48. Intervention Week consisted of a training session of 1 hour's duration for each group of officers.

DATA COLLECTION

Four sets of data were gathered for this study:1) Monthly police statistics on charges laid for

drinking-driving offences for each officer were collected for 1980.

2) Drinking-driver suspect forms were gathered from each officer for the pre- and post-intervention periods. These forms were to be completed every time an officer stopped a driver suspected of drinking, regardless of whether or not the driver was arrested. Information was obtained on the date, time of stop, age and sex of driver, charge (s) laid if arrested, breath analyzer readings if taken, and the cues the officer used in suspecting that the driver had been drinking.

3) Two sets of questionnaires were also used. Prior to the pre-intervention and immediately following the post-intervention period, a drinking-driving enforcement questionnaire regarding training attitudes, and motivation towards enforcing the drinking-driving laws was administered.

4) Additionally, the officers completed an evaluation of the training programs at the end of the training session.(2 ) The 23 cues from the Harris package were randomly

ordered into a list and "accident-related" and "other"were added. The officers were asked to check no morethan 3 as their reasons for investigation.

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RESULTSAll but 1 of the officers were male, with an average

age of 32.3 years (range: 22-46 years), with an average 73.2 months or 6.1 years of experience (range: 2 months - 20.3years), and had made an average 1.2 drinking-driving arrests during the Year 1980 (range: 0-4 arrests). Over a 10-month period, a total of 183 drinking-driver suspect forms were submitted by the officers: 43.2% (n=79) of these forms were completed by the experimental group and 56.8% (n=104) ofthese forms, by the control group. From this sample, 68.9% (n=126) of the suspected drivers were arrested for Criminal Code offences: 85% (n=102) of those arrested were charged under the Criminal Code Section 236 "over 80"; 8.3% (n=10) charged under Section 234 "Impaired"; 4.2% (n=5) chargedunder Section 235 (2) "Failure or refusal to provide a breath sample"; and 2.5% (n=3) charged under Section 233 "Criminal negligence or dangerous driving." However, 19.9% (n=36) of the drivers stopped were not arrested but charged under the Liquor License Act (L.L.A.) or Highway Traffic Act (H.T.A.) (for example, "careless driving"). Only 11.6% (n=21) of the drivers stopped were neither arrested nor charged. (Table 1 summarizes these results).

Of all the drivers stopped, 90.6% (n=164) were male.Of this population, 37.8% (n=62) were between the ages of 16 and 24 years, 32.9% (n=54) between 25 and 34 years, and29.3% (n=48) were 35 years or over. The majority ofvehicles, 54.2% (n=99) , were stopped between 0001 to 0700hours— only 28.6% (n=52) between 1901 to 2400 hours— mostfrequently on Friday and Saturday nights.

The drinking-driver suspect forms also provided the data to obtain the weekly arrest rates for each group of officers. The arrest rates were calculated from the suspects who were stopped, arrested, and subsequently charged under C.C. Section 234, 235 and 236. A logtransformation was performed on the data to stabilize the variance (Figure 1) . Because of low, nonsignificant autocorrelations, the data were subjected to a 2 (group) x 2 (phase) repeated measures analysis of variance (ANOVA; see Table 2). A significant main effect was found for subjects (p greater than .05) and a near significant main effect for phase. The only significant interaction was Subject x Group (p greater than .05). The Subject effect reflected the fact that older officers tended to have lower arrest rates when compared to younger officers. The near significant maineffect for phase was due to the fact that thepre-intervention mean arrest rate was 0.79, whereas the post-intervention mean arrest rate was 1.33 (Table 3). That is, there was an increasing trend in overall arrests after the intervention.

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Summary of Analysis of Variance of Arrest Rates Over the Pre- and Post-Intervention Phases by Group

Table 2

SOURCE DF ANOVA SS F VALUE P

SS 11 33.0625 3.29 0.03

Group 1 0.0208 0.02 0.88

Group SS 11 37.2291 3.70 0.02

Phase 1 3.5208 3.85 0.08

Phase SS 11 14.7291 1.46 0.27

Group Phase 1 0.1875 0.20 0.66

Error 11 10.0625

TOTAL 47 98.8123

Table 3

Mean Arrest Rates of the Experimental and Control Groups for the Pre- and Post-Intervention Phases

Mean Weekly Arrest Rates

Pre-Intervention Post-Intervention

Experimental 0.83 1.25

Control 0.75 1.42

TOTAL 0.79 1.33

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The trends observed in the ANOVA results indicated the need to investigate further the officers' abilities to discriminate between DWI1s and DWS's. To evaluate the groups' performance for pre-post intervention, we computed a score to measure the officers correct detection rate. This rate was represented by the number of suspect forms for which an arrested driver was registered on a breath analyzer 80 mg% or over for a first reading, divided by the total number of suspect forms submitted for each period by each group.

Correct detection rate = Number of suspect forms(when BAC greater than 80 mq%)

Total number of suspect forms submitted

The data were subjected to logit analysis, and onlyperiod showed a significant mean effect (Chi-sguared=8.09,df=l, £ greater than .01). The detection rates for bothgroups were higher after the intervention (Table 4).

Table 4

Detection Rates by Group Over Time

Group

Period Experimental Control

Pre Intervention .438 .412

Post Intervention .813 .762

A more detailed analysis was carried out on the detection cues by analyzing the "reasons for investigation." Three hundred and seventy four reasons for investigation were checked off on the 183 completed suspect forms. "Accident related" stop figured predominantly, despite it not being a detection cue. Other idiosyncratic cues were also frequently offered, such as, suspect driving with man standing on rear bumper, asleep on the side of the road, and

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squealing tires. One final problem occurred with the cues: unfortunately, half way through our program Harris et al.(1980) removed 3 cues from the original list, thus, when all the cues not contained in the Harris package were excluded from the count, 117 reasons remained. The most common cues were swerving (14.5%), drifting (12.8%), and weaving (10.3%).

The cues from the original guide were collapsed into 2 groups: those whose probabilities were greater than or equal to 50 and those whose probabilities were less than 50. If the package were an effective training program, we should expect the experimental group after training to use more cues with higher probabilities in their decisions to stop in relation to the cues they used before training and in comparison to the control group (Table 5) . Logit analysis of cue choice, by group and period, yielded only 1 significant result. Significantly more cues were chosen from the "50 and over" cue category than from the "under 50" cue category (Chi squared=17.52, df=l, p less than .001).

The analyses of the questions on motivation, training, and attitudes found nothing significant.

The final analyses were on the police officer's assessment of the training programs. No differences were found between groups on the assessment of their respective training packages. Of the officers, 57.2% (n=12) agreed orsomewhat agreed that the training session improved their performance to detect drinking drivers, 33.3% (n=7)disagreed or somewhat disagreed, and 9.5% (n=2) wereundecided. Only 23.8% (n=5) agreed or somewhat agreed thatthe training session improved their ability to get convictions in court; the same number remained undecided, and over 52.4% (n=ll) responded in the range of somewhat disagreed to strongly disagreed. Also, 50% (n=10) of theofficers disagreed and somewhat disagreed that the training session changed any of their previous attitudes or beliefs concerning drinking-driving violations, 40% (n=8) wereundecided, and 10% (n=2) somewhat agreed.

CONCLUSIONS

The results of this pilot test of the Harris DWI visual detection training program show that it is as good as an informal discussion on drinking and driving in increasing arrest rates. This means that the near significant increases in arrest rates were most likely due to the

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message given to the police that drinking-driving enforcement had become a high priority item through the introduction of training for DWI detection. Our data gave no suggestion that the experimental group shifted their criteria for DWI detection. Indeed, the results showed that both groups of officers tended to choose the cues with high probability of DWI throughout the study. In other words, they had been using the right cues all along. This is not surprising, given that the cues were originally developed from pooling detection cues used by samples of American officers. For this reason, it may be that this training package is of limited value to experienced officers. In fact, the conclusions of the Barrie officers were that they knew which cues were indicative of impaired driving and, in fact, other factors affected their arrest rates. The consensus was that the training program might be useful to recruits who do not have the benefit of experience but it is of little value to experienced officers. However, it is important to point out that perhaps the officers were not using the cards and training as well as they could, and perhaps with more training their performance could be improved. Furthermore, the program did derive some benefits, because arrest rates did seem to increase. Therefore, we conclude that the DWI Detection Guide, as Harris et al. (1980) found, did increase arrest rates but, most likely, through the general impact of training per se rather than the specific impact of the probabilistic cues.

ACKNOWLEDGEMENTWe would like to particularly acknowledge the

assistance of Chief E. Snider and Inspectors R. Berry, K. McKenzie, and R. Pickard.

REFERENCES

Arthur Young & Co. (1974). Factors Influencing Alcohol Safety Action Project Police Officer's DWI (Driving While Intoxicated) Arrests. Report No. DOT-HS-123-3-774. Washington, D.C.: National Highway Traffic SafetyAdministration.

Beitel, G. A., Sharp, M. C. , and Glauz, W. D. (1975). Probability of arrest while driving under the influence of alcohol. Journal of Studies on Alcohol, 36: 109-116.

Borkenstein, R. F. (1972). A panoramic view of alcohol, drugs and traffic safety. Police, 16: 6-15.

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Borkenstein, R. F. (1975). Problems of enforcement, adjudication, and sanctioning. In Israelstam S., and Lambert S. (eds.), Alcohol, Drugs, and Traffic Safety.Toronto: Addiction Research Foundation.

Bragg, B. W. E., and Wilson, W. T. (1980). Evaluation of a performance test to detect impaired drivers. Accident Analysis & Prevention, 12: 55-65.

Harris, D. W. , Howlett, J. B., and Ridgeway, R. G.(1979). Visual Detection of Driving While Intoxicated. Project Interim Report: Identification of Visual Cues andDevelopment of Detection Methods. Report No. DOT-HS-80501. Washington, D.C.: National Highway Traffic SafetyAdministration.

Harris, D. H. , Dick, R. A., Casey, S. M. , and Jarosz,C. J. (1980). The Visual Detection of Driving WhileIntoxicated: Field Test of Visual Cues and DetectionMethods. Report No. DOT-HS-7-1538. Washington, D.C. : National Highway Traffic Safety Administration.

Lawson, J. J. (1983). Calculation of chance of arrest for alcohol impairment. Transport Canada Memorandum.

N.H.T.S.A. (1980) . Alcohol and Traffic Safety Workshop Series, 1980-81. Washington, D.C.: National Highway Traffic Safety Administration.

Nichols, J. L. , Weinstein, E. G., Ellingstad, V. S., Struckman-Johnson, D. L. , and Reis, R. E. (1981). The effectiveness of education and treatment programs for drinking drivers: A decade of evaluation. In Goldberg, L.(ed.), Alcohol, Drugs, and Traffic Safety, Stockholm: Almqvist and Wiksell International.

Pagano, M. R., and Taylor, S. P. (1979). Police perceptions of alcohol intoxication. Journal of Applied Social Psychology, 10: 166-174.

Picton, W. R. (1978) . Legislation to allow the safe release of potentially unsafe drinking drivers. Roadside Surveys of Drinking-Driving Behaviour: Two Pilot Projects,Catalogue No. T46-6. Ottawa: Information Canada Catalogue.

Vingilis, E., Blefgen, H., Colbourne, D., Reynolds, D., Wasylyk, N. , and Solomon, R. (1983). Ontario police officers' enforcement and perceptions of drinking-driving laws. Presented at 9th International Conference on Alcohol, Drugs, and Traffic Safety; San Juan, Puerto Rico; November 13-18.

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D J F M A M J J A S OMONTHS

Figure 1. Total monthly arrests for the pre- and post-intervention phases.

1 4 0 5

TABLE 1 SUMMARY OF THE DETECTION OF SUSPECTED DRINKING DRIVERS

NUMBER OF DRINKING DRIVER SUSPECT FORMS

N = 183

EXPERIMENTAL GROUP

N - 79

ARRESTED

CONTROL GROUP

N = 104

ARRESTED

YES

N = 55

CHARGES

NONE 2234* 6235** 1236*** 45OTHER+ 1

NO

N = 24

CHARGES

NONE 9 OTHER+ 15

YES

N = 71

CHARGES NONE234* 235** 236***OTHER+MISSING

24457

22

NOn = 33

CHARGES NONE 12 OTHER+ 21

IMPAIRED DRIVING ** REFUSAL TO PROVIDE BREATH SAMPLE

*** OVER 80+ OTHER = CHARGES UNDER HIGHWAY TRAFFIC ACT OR

LIQUOR LICENCE ACT

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