2 - METHOD

The materials reviewed here are those dealing with the drug-crash problem created by various groups of drivers. The scope of the review included foreign as well as U.S. literature with a direct bearing on highway safety. The review covers the period 1980 to the present and addresses the following four major areas of research:

The review emphasizes controlled substances to include marijuana, benzodiazepines, non-benzodiazepine sedative and hypnotic drugs, and others such as amphetamines, cocaine, hallucinogens, and narcotic drugs. However, research related to any other drugs having the potential to significantly impair driving is also included in the review. Applicable research conducted in foreign countries, and documented in the English language, is included.

Specific topical areas examined for literature are:

ISSUES

Major issues considered when reviewing a document were:

SOURCES OF LITERATURE

Literature sources included collections and individual documents that have not been placed in traditional collections. Types of repositories that were contacted include:

The UMTRI library was the central focus and coordinating element of the literature search and collection activities. The research library at Purdue University was also accessed in the literature search.

LITERATURE SEARCH PROCEDURES

The starting point in the search was recent bibliographies and reviews of directly related materials. Relevant bibliographies and reviews were identified through a search of the UMTRI library, and through discussions with subject-matter experts (including a project advisory group) and others.

The next step in the search was to examine specific journals and conference proceedings known by the principal investigators to contain pertinent materials. These documents were not necessarily concerned directly with highway safety, but tended to focus on other related disciplines such as human factors, toxicology, and drug studies in general.

Another source considered for this review is material generated by the various Drug Evaluation and Classification (DEC) programs throughout the country. This material appears in different forms, including newsletters and pseudo-journals that report claims on the accomplishments of the programs, some of which are supported by data. NHTSA staff in Washington identified a number of contacts for gaining access to such materials.

Each document acquired through the literature search was screened for inclusion in this review. Two levels of screening were performed: (1) an initial screening to determine whether a document should undergo further substantive examination by the Principal Investigator (Mr. Jones), and (2) a final screening by the Principal Investigator of documents surviving the initial screening. Criteria contained in each these levels are indicated below:

Failure of a document to meet either of the Level-1 criteria resulted in its elimination from the review. However, documents that met Level-1 criteria but were flawed with respect to one or more Level-2 criteria were not necessarily rejected. For example, a study that was well-designed and executed, but made conclusions that did not flow from its findings might have been kept in the update. The update's commentary on that study noted the inconsistencies between the research results and the conclusions, and offered a more consistent interpretation of the results. Some other flawed studies that were being widely quoted in the non-scientific literature were retained simply to document their flaws.

Finally, the last step in conducting the update was the preparation of this document, the update report. Bibliographic information on each article was entered into a computerized bibliographic database.