- Functional limitations and physical vulnerability
- Functional limitations, diseases and medication
- Physical vulnerability
Functional limitations and age related disorders do not automatically lead to unsafe traffic behaviour. Other characteristics of older road users can prevent safety problems. They include the insight into one's own limitations, driving experience, and compensatory behaviour such as driving when the roads are less busy or when it is daytime and dry. One can think of various ways that older people have the possibility to compensate. In the first place they often have more freedom in choosing the moment to travel. Various studies have shown that older people more often choose to drive during daytime and dry weather. In the second place older people on average have a great deal of driving experience. The traffic insight they have acquired may give them the ability to anticipate on possible problematic situations. In the third place, the diminishing desire for excitement and sensation when getting older possibly plays a role. In keeping with this, older people, on average, less often drink-drive than younger adults and generally obey the traffic rules more frequently .
With regard to compensation for functional limitations, Jansen et al.  identified four different compensation styles among older drivers which account for 84% of their study participants (the compensation styles of the remaining 16% could not be identified):
- Functional compensation (23.4%): people are aware of their deficits and report adequate changes of driving behaviour.
- Dysfunctional compensation (5, 5%): people are aware of their deficits, but do not report adequate changes of driving behaviour.
- Preventive behaviour (24, 9%): people are not aware of their deficits, but they report adequate changes of driving behaviour.
- Missing compensation (30 %): people are not aware of their deficits, and they do not report adequate changes of driving behaviour.
Possibilities for compensatory behaviour
According to the hierarchic structure of the driving task proposed by Michon (1971, 1985), there are three levels of skill and control: strategic, tactical and operational. Possibilities for compensatory behaviour are offered especially at the higher levels of control. On these higher levels (strategic and tactical), there is hardly any pressure of time, giving the driver enough time to make the right decisions. Examples of the kind of decisions that are made on the strategic level are "when and how to drive to a certain destination". On the tactical level, decisions are made on the distance that should be kept to the vehicle in front, and whether or not to overtake. On the operational level, one has only milliseconds to decide on braking and steering. But by deciding on a longer distance from the vehicle in front (at the tactical level), one will have more time to react and operate. Similarly, by reducing speed at the approach of an intersection, one will have more time to respond to the information given by the traffic environment.