Assisting the older driver - SWOV

Assisting the older driver
route instructions for surrounding traffic and the resulting speed reductions
of these vehicles may have exaggerated the proportion of unsafe driver
decisions at roundabouts and three‐way intersections with a side‐street at the
driver’s right‐hand side.
6.4.2. Functional age
With regard to functional age it was found that functional age affects
workload as soon as people start driving. The reaction times of drivers of
different functional age groups were the same when they had to carry out a
detection task while they were sitting in a parked simulator car. However,
when performing the same task while driving, functionally old drivers had
longer reaction times than both functionally young and middle‐aged drivers.
This can be attributed to the age‐related increase in the cost of dividing
attention (see e.g., McDowd, & Craik, 1988; McDowd, Vercruyssen & Birren,
1991; Salthouse, 1991). As traffic situations got more difficult, the workload
of all drivers increased further. However, this increase in workload did not
increase with functional age. An interaction effect was only established for
the increased effort needed to combine the primary and secondary task. In
that case, functionally old drivers experienced a higher increase in workload
than young drivers did. Whereas functional age did affect workload, this age
effect was not established for safety of decision making. All age groups
appeared equally capable of deciding whether it was safe to cross or join
other traffic streams.
The fact that functional age only affected workload and not safety of driver
decisions, can be the result of three related things. First of all, it may indicate
that our functionally older drivers were capable of adequately compensating
for their increased reaction time. Another explanation may be that our
simulator environment did not sufficiently put our drivers to the test.
Perhaps task demand should have been higher to overask the capabilities of
the functionally older driver and affect the safety of his decisions. On the
other hand, our functionally older drivers may have been too young to find a
safety effect of intersection design. After all, they were people who still drove
on a regular basis and did not have considerable functional limitations.
Therefore, it is recommended that future studies investigating the differential
effects of intersection design on driver behaviour of older and younger
drivers either include drivers with more severe functional limitations or
confront drivers with traffic situations that are more difficult to pass.
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