If there is one field in which it is absolutely essential for policies to be drawn up on the basis of sound scientific evidence, it is road safety, or more particularly driving under the influence of substances which adversely affect one's ability to drive.The number of people who drive after drinking alcohol or taking medicines or other psychoactive substances, both legal and illegal, alone, in combination or in succession, is very high, and in many European countries this number is constantly rising.The Pompidou Group organised a meeting bringing together 66 experts to take stock of the situation. Five working groups looked at legal aspects, prevalence and risk assessment, problems in the field of policies practices, prevention and substitution treatment issues.This book contains the background reports, the presentations given at the seminar, and the conclusions and recommendations made at the close of the meeting.