Assisting the older driver - SWOV

Current state of the art: crashes and injuries
However, the most important conclusion that can be drawn from Table 1.1 is
that older drivers not only have a higher than average injury rate, but are
also more often legally responsible for the crashes they are involved in. This
offers possibilities for developing measures that prevent the crash types for
which the older driver is legally responsible. It is expected that these
measures will lead especially to a decrease in their crash involvement, and
with it the fatality rate of the older driver, if the crashes they are involved in
are the result of functional limitations instead of (wilful) risk‐taking
behaviour. In Section 1.3, it is examined whether there are indeed crash types
that are over‐represented among older drivers, and if so, how they can be
characterized. The next section discusses another factor that may influence
the older driver’s fatality rate: annual mileage.
1.2.4. Role of annual mileage
Older drivers typically drive a shorter distance per trip and hence have lower
accumulated driving distances per year. In general, drivers travelling more
kilometres have reduced crash rates per kilometre compared to those driving
fewer kilometres. Therefore, the low mileage of older drivers may exaggerate
older driver risk per kilometre estimates (Janke, 1991). Several studies, using
data from different countries, have tested this hypothesis (Fontaine, 2003;
Hakamies‐Blomqvist, Raitanen & O’Neill, 2002; Holte, 2005; Langford,
Methorst & Hakamies‐Blomqvist, 2006). They all found that when driver
groups were matched for yearly mileage, age‐related increases in crash rates
per km disappeared. That is, older drivers with an average or high annual
mileage have crash rates that are comparable to those of younger adult
drivers with the same annual mileage. Only drivers with a low annual
mileage have more crashes per million driver kilometres, but this goes for
younger drivers as well as for older drivers.
Crash rates can also be biased by the type of roads typically travelled by
older drivers. Many avoid driving on motorways (with interchanges), the
safest types of roads, and tend to drive on streets with intersections, which
are, by their very nature, less safe and have more crashes (Janke, 1991).
Hence, older drivers’ risk estimates based on injuries or fatalities per mile
driven will be overestimated when compared to those of younger drivers
with higher yearly mileage on safer roads (OECD, 2001).
23