Driving under the influence of drugs or impairing medicines reduces fitness to drive[i] and increases crash risk. Drugs have a numbing, stimulating or mind-altering effect on the brain, or a combination of these effects, which impair traffic task performance.

In the Netherlands, a sustainable road safety approach, in which measures in the fields of Engineering, Education and Enforcement (3Es) are complementary, has been used for decades. Enforcement reduces high-risk road user behaviour and is therefore an important component of this safe system approach.

Driver fatigue is estimated to be a (contributing) factor in 15 to 20% of crashes, but estimates in individual studies vary widely. Drivers who are tired are less attentive and react less quickly and less adequately than drivers who are not tired. They also get irritated and frustrated more easily.