Abstract: This Thematic paper presents the key findings of the European Union’s research project on Driving Under the Influence of Drugs, alcohol and Medicines, known as the DRUID project. The project looked at experimental studies, epidemiological studies, enforcement, classification of medicines, driver rehabilitation, withdrawal of driving licence, and dissemination and guidelines. Over 5 years of work across 18 countries, the project has produced some 50 reports, each one contributing key evidence to road safety policy. The thematic paper therefore aims to summarise the findings of one of the biggest research projects ever carried out in the EU on drugs and driving.