High fatality rate: more crashes or more severe injuries?

Older drivers have a relatively high fatality rate. Data from the Netherlands illustrates this. Taking the distances travelled into account, the fatality rate for car drivers is more than five times higher for the 75 years and older than for the average for all ages. That of the 65 to 74-year-olds is much lower. However, other means of transport are not safer. The fatality rate is particularly high for older cyclists. The rate is about 12 times higher for the 75 years and older than for 'the average cyclist'. Compared with the fit group of 30 to 49-year-olds, the difference is even larger:

Unfortunately, cross-national comparisons at this level of detail (fatality rate by age and mode of transport) are not possible. The international databases that contain crash data of several European countries do not include data on fatalities per means of transport per age group. The data for the Netherlands, however, is comparable to that of the other European countries, although the number of pedestrian fatalities seems to be somewhat lower than in other countries [81]. Cross-national comparisons of the number of fatalities and of fatality rates for all road users aged 65 years and above (regardless of means of transport) can be found in SafetyNet's Traffic Safety Basic Facts on The Elderly.

High fatality rates can be caused either by higher crash rates or by greater fragility. The fragility of a group of road users is reflected in the difference between their fatality rate and injury rate, but also in their fatality ratio: the percentage of fatalities in the total number of casualties.

Fatality rate versus injury rate for different age groups

Older drivers have the second highest fatality rate. Only the youngest group of drivers (18- and 19-year olds) has a higher fatality rate. The figure on the left shows the well-known U-shape: fatality rates of the young drivers are high, after which the rate declines to a minimum for drivers of the age of 40-60 years. Then it increases again, to a maximum for those aged 75 and older. The injury rates, depicted in the figure on the right, also show a U-shape, but this one levels off on the right-hand side. Whereas young drivers (18-24 years old) have a relatively high injury rate as well as a high fatality rate, the injury rate for older drivers is much lower than their fatality rate.

To explain this difference between young and older drivers, data is needed on the two underlying aspects of both rates: crash involvement and fragility. Crash involvement indicates how often a particular group of road users is involved in a crash (of a particular severity), without giving insight in the injury of the group of road users concerned. Fragility indicates the average injury severity of a particular group of road users.

Crash rate of older drivers in comparison with other age groups

A comparison of the crash rates for fatal and non-fatal injury crashes for different age groups shows that the youngest group of drivers is much more often involved in these types of crashes than the other age groups. The group of drivers aged 75 and above has the second and third highest crash rate for fatal and non-fatal injury crashes respectively. However, the difference between the fatal crash rate for the youngest and that for the oldest group is much larger than the difference between their fatality rates. Therefore, it seems that the fatality rate of young drivers is influenced more by their crash involvement than is the case for those aged 75 and above. The high fatality rate of the latter age group is probably determined to a larger extent by their fragility.

A confounding factor in the relationship between crash involvement and fatality rate is crash type. Some age groups may have crashes that typically have greater impact, such as running off the road or crashes while driving at a higher speed. Driver behaviour also plays a role here. Older people, on average, less often drink-drive than younger adults and generally obey the traffic rules more often.

Fatality ratio of older drivers in comparison with other age groups

Fragility can be expressed as the number of fatalities per 100 injured victims or as the percentage of fatalities in the total number of casualties. The latter is called the fatality ratio [79]. This ratio increases with age and is higher for unprotected road users such as pedestrians (see also physical vulnerability):