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.

Children are a vulnerable group among road users. They are, after all, still building up skills which will eventually allow them to become safe and independent road users. The role of parents in teaching their children how to behave safely in traffic is very important.  In this fact sheet, children are taken to belong to the age category 0 to 14, unless specified otherwise.

A progressive penalty system encompasses heavier or more far-reaching sanctions being imposed as one commits more offences. A progressive penalty system is often called a progressive fines system if it involves increasingly higher financial penalties (fines), but (other) recidivism schemes such as demerit points systems can also be seen as a progressive penalty systems.

The elderly have a higher than average fatality rate in traffic. The most important cause of this high fatality rate among the 75 year olds and older is their greater physical vulnerability. In addition, functional limitations can lead to the elderly more frequently being involved in certain types of crashes.