How many crashes are caused by risky road user behaviour is unknown. For road crashes, police do not register whether they involved risky road user behaviour. Yet, something can be said about risk increases associated with specific risky behaviour.
For risky road user behaviour prioritised by enforcement, such as drink-driving, speeding and distracted driving, information about the risk of road deaths or crashes is available. It is estimated that 12% to 23% of Dutch road deaths are caused by drink-driving (see SWOV fact sheet Driving under the influence of alcohol). International research shows that about one third of fatal crashes is related to speeding (above the limit) or inappropriate speed (unadapted to the prevailing conditions); see SWOV fact sheet Speed and speed management. There are no recent Dutch estimates of the number of crashes caused by distraction. American 2017 crash figures show that distraction is involved in 9% of registered fatal car crashes and that 6% of drivers involved in a fatal crash were distracted [27] (see SWOV fact sheet Distraction in traffic). Driver fatigue, although not an enforcement priority, is involved in 15 to 20% of crashes (see SWOV fact sheet Fatigue).
Less is known about the effect of other risky road user behaviour (red light negation, cycling without lights, insufficient headway time) on the number of crashes, but there is some knowledge about risk increasing factors and what part they play in specific types of crashes. Studying fatal crashes at signalised 50km/h-intersections shows that in 41 to 67% of these crashes red light negation certainly or possibly played a part [28]. Furthermore, red light negation is estimated to increase crashes of this type 14 times [28]. In the dark, not having or not using front and rear bicycle lights increases the risk of getting involved in a bicycle crash by an estimated 17% [29]. However, the researchers note that the uncertainty of the estimates is significant. Moreover, the quality of the bicycle lights was not taken into account either (the results relate to bicycle lights common between 2002 to 2010). Also see SWOV fact sheet Public lighting and vehicle lighting.
In the United States, it was previously estimated that over 50% of fatal crashes were possibly related to risky (or aggressive) behaviour [30] including speed violations, too short headway times, giving right of way, incorrect overtaking, but also to omitting to indicate direction, or sudden speed changes.
For research purposes, information about repeat offences is only available at vehicle level (the actual operator of the vehicle is unknown). Goldenbeld et al. [26] found that the group of vehicles involved in nine or more offences a year, is involved in over 6% of crashes, while this group constitutes less than 0.5% of the offender population.
