Our review indicates that very little effort has been devoted to developing and operating countermeasures for drug-impaired driving. This is no doubt due, at least partially, to society's recognition that the magnitude of the drug-crash problem is much smaller (perhaps one to two orders of magnitude smaller) than that of the alcohol-crash problem. Consequently, society has responded rationally by putting forth less effort toward dealing with the drug-crash problem than it has toward dealing with the alcohol-crash problem.

Whereas there is now a large body of literature covering a range of countermeasure approaches for the alcohol-crash problem (5), nearly all of the very sparse literature on drug-crash countermeasures is concerned with a single approach. That approach involves the use of the Criminal Justice System to create, enforce, and adjudicate laws prohibiting drug-impaired driving, and to impose sanctions on persons convicted of violating such laws. Further, a single function of the Criminal Justice System, enforcement, has received virtually all of the attention in the literature. And, within the enforcement function, only activities involved in processing a motorist who has been stopped (for example, performing behavioral and chemical tests to determine impairment) are addressed in the literature.

This chapter discusses this literature as it pertains to countermeasures in the United States and in other countries as well.


Countermeasure Programs in the United States

For the most part, the enforcement of laws against drug-impaired driving has been performed in concert with the enforcement of laws against alcohol-impaired driving. In general, the laws are written in such a way as to proscribe driving while impaired by any substance, be it alcohol or some other drug. However, while in most states impairment is described rather precisely in terms of BAC for alcohol, it is described much more subjectively or not at all for other drugs. Some states limit the types of drugs covered in their law to controlled substances, that is, those substances that are controlled by the Federal government according to their potential for abuse and their accepted medical use in treatment. And in some states, the mere presence of illegal drugs constitutes a drug-driving violation. Also, some state laws explicitly prohibit driving while impaired by a combination of alcohol and other drugs. (6)

There are three main types of driving under the influence of drugs (DUID) statutes: (1) Statutes requiring that such a drug render a driver incapable of driving safely; (2) Statutes requiring that the drug impair the driver's ability to operate safely or require a driver to be under the influence or affected by an intoxicating drug; and (3) zero tolerance per se laws which make it a criminal offense to have an illicit drug or metabolite in the body (bodily fluids) while operating a motor vehicle.

All of the states save Texas and New York use the phrase "under the influence" in their DUID statutes. A total of fourteen states (Alabama, Arkansas, Illinois, Kansas, Nevada, Maryland, New Mexico, North Dakota, Oklahoma, Pennsylvania, South Dakota, Vermont, Wisconsin, and Wyoming) define the standard that constitutes "under the influence" within the body of the statute as "incapacity"; that is, the influence of the drug "renders the driver incapable of safely driving." Incapacity to drive safely is thus linked to the drug ingested, and the prosecutor must show a connection between drug ingestion and the incapacity of the driver.

Eight states (Arizona, Florida, Hawaii, Indiana, Kentucky, Montana, South Carolina, and Virginia) use the standard of impairment to define "under the influence" such that the influence impairs the person's driving abilities. This suggests a requirement of proof that is less stringent than one that renders the driver "incapable" of safely driving; nevertheless, the prosecutor must still prove that the impairment is directly related to the drug ingested.

As a result of the overall prevalence of drug abuse in the nation and the growing body of evidence of illegal drug use by drivers, eight states (Arizona, Georgia, Iowa, Illinois, Indiana, Minnesota, Rhode Island, and Utah) have enacted so-called "zero tolerance" laws which make it a criminal offense to operate a motor vehicle while having a drug or metabolite in one's body or bodily fluids. Under such statutes, individuals can be found guilty of violating the law if he/she were operating a motor vehicle while any amount of prohibited substances were present in his/her system.

The most extensive U.S. program dealing with the enforcement of drug-impaired driving laws is NHTSA's Drug Evaluation and Classification program (DEC). The DEC program was an outgrowth of a program developed by the Los Angeles, California Police Department (LAPD) in which officers were trained to become Drug Recognition Experts (DREs), and as such, to recognize behaviors and physiological states associated with seven categories of drugs, viz., narcotic analgesics, CNS depressants, CNS stimulants, phencyclidine (PCP), cannabis, hallucinogens, and inhalants. A major objective of the program was to determine whether stopped drivers exhibiting the symptoms of alcohol impairment, but with low BACs, were impaired by some other drug. There are currently 36 states with DEC programs, and approximately 6,000 officers have received Drug Recognition Expert (DRE) training.

NHTSA sponsored two evaluations of the LAPD program, the first in collaboration with the National Institute on Drug Abuse (NIDA) and concerned with subject examination procedures (Bigelow, Bickel, Roache et al., 1985), and the second concerned with the program as a whole (Compton, 1986). The two evaluations found that LAPD's drug recognition procedure enabled police officers to recognize the symptoms of many types of drugs used by drivers suspected of drug use. Also, the DREs were able to correctly identify at least one drug in most of the suspects they judged to be impaired by drugs, and were able to correctly identify all of the drugs detected in about half of the suspects.

Evaluations of the DEC program in other jurisdictions were published in 1992, 1994, and 1996. A study by Preusser and associates (1992) evaluated DEC programs in selected sites in the states of Arizona, California, Colorado, New York, and Texas over various periods during 1986 to 1991, finding that most of the DRE opinions were confirmed by chemical tests and that most of the confirmed suspects were convicted. Jernigan (1992) performed a preliminary evaluation of Virginia's DEC program using data from the period 1988-1990. The program was a response to a 1988 Virginia law giving police officers the authority to require a driver to submit a blood sample to be tested for drugs. Jernigan concluded that the law helped increase arrests for DUI, but that DRE cases were no more likely to result in a conviction than non-DRE cases. Also, Jernigan found no evidence that the law reduced traffic crash injuries or fatalities.

Adler and Burns (1994) evaluated the Arizona DEC program using data from the January 1989 - May 1993 period. They found the DREs' decisions regarding the suspects, impairment and the drug categories creating the impairment to be highly accurate and concluded that the DEC program was a valid method for detecting and classifying drug-impaired drivers. Similar positive conclusions about DREs' ability to predict drugs in suspected impaired drivers were drawn in an evaluation of DRE performance in Denver, Colorado (Tomaszewski, Kirk, Bingham et al., 1996).

Recently, Shinar, Schechtman, and Compton (2000) evaluated DREs' actual performance in detecting drug impairment and in identifying the drug category causing the impairment. Four drug classes were tested in the study, cannabis, depressant, narcotic analgesic, and stimulant. Drug doses were administered by a nurse under the supervision of a physician, and the DREs were told that the subjects may be under the influence of none, one, or two or more drugs of any type except hallucinogens and inhalants. A total of 54 subjects participated in the experiment, and each subject was tested in six sessions over a period of six weeks spent as an in-patient. The tests were an abridged form of the standard DEC test protocol, containing all of the elements of the standard test series except the interview with the arresting officer.

The study indicated that the DREs' ability to distinguish between subjects who were impaired and subjects who were not impaired was, in the words of the authors, "moderate at best." The DREs' ability to identify the drug class causing the impairment varied from "moderate" (for alprazolam) to "lower" (for cannabis and codeine) to "not better than chance" (for amphetamine). Further, the DREs relied on just one or two "pivotal" symptoms in making their diagnoses, rather than utilizing all of the information they had available as recommended by the DEC manual. The authors recommended that future training include formal models for synthesizing information and that the DEC protocol include the use of the interview and the arresting officer's report to check the results of the testing of physical signs and symptoms.

Countermeasure Programs in Other Countries

The literature we found deals almost entirely with European countries and indicates that, in most countries, a drugged driving violation requires proof of impairment due to the drug (ICADTS Working Group on Illegal drugs and Driving, 2000). However, Germany, Belgium, and Sweden have laws similar to the United States per se law for alcohol, prohibiting driving with the presence of any amount of illegal drug as determined by a chemical test of a body fluid.

The International Council on Alcohol, Drugs and Traffic Safety (ICADTS) has summarized the status of drugged driving countermeasure activity in Europe in its recent report referenced above. Information used in the report was obtained from a survey of ICADTS members and affiliates in 17 countries. Overall, as in the United States, countermeasures focus on enforcement of criminal statutes prohibiting drugged driving however defined. Clinical determination of impairment, roadside testing, laboratory testing, or all three may be required to establish impairment, depending on the country. A recent Belgian law explicitly allows the use of roadside urine tests as a component of its procedure to determine the presence of illicit drugs. Some countries (for example, Germany) have a procedure similar to the one used by DREs in the United States to determine impairment.

There is evidence that the drugged driving problem has begun to get more attention in Europe. Several initiatives involving multiple countries have been created and are examining the technological, legal, and operational aspects of drugged driving enforcement. Organizations include the Council of Europe (41 member states) and its Pompidou Group, founded to combat drug abuse and illicit trafficking in drugs; the European Monitoring Center for Drugs and Drug Addiction; and the European Transport Safety Council. Detailed recommendations for improving Criminal Justice System responses to the drugged driving problem in Europe are included in a recent report published by the Pompidou Group (Krueger, Perrine, Mettke et al., 1999).


The literature indicates that countermeasure approaches in the United States and Europe have involved the use of the Criminal Justice System to enforce drugged driving laws using methods similar to those used in enforcing DWI laws. The major emphasis appears to be the identification of impairment among stopped drivers using chemical tests and / or clinical assessments. In Europe, both approaches are used, the approach used depending on the country. In the United States, the emphasis is on the clinical approach as embodied in the Drug Evaluation and Classification program, (DEC).

Three evaluations of DEC found good agreement between assessments and chemical tests, but a more recent evaluation found problems in differentiating drivers who were impaired from drivers who were not impaired, and also found problems in identifying drug classes causing impairment.

Finally, we found no evaluations the impact of any drugged driving countermeasure on crashes, either in the United States or Europe. This might be expected, given the lack of any databases containing objective measures of the presence of drugs in crash-involved drivers.

5These approaches are discussed at length by Jones and Lacey (2001) in a recent update of the literature on the state of knowledge of the alcohol-crash problem.

6 A summary of state laws on driving while impaired. These approaches are discussed at length by Jones and Lacey (2001) in a recent update of the literature on the state of knowledge of the alcohol-crash problem.nited States may be found in a report by Walsh et al. (2002).