Assisting the older driver - SWOV

Assisting the older driver
6.4. Discussion and conclusions
The aim of this study was to identify those intersection characteristics that
have the largest impact on the difficulty of passing intersections, as indicated
by driver workload and safety of driver decisions. A distinction was made
between the performance of functionally young and functionally older
drivers. The latter group of drivers was expected to have more difficulties
passing complex intersections than the younger group. The complexity of an
intersection was expected to increase with the number of streets and lanes it
connects, and to be dependent on the type of priority regulation and the
participants’ view of the intersection.
6.4.1. Intersection characteristics
The results of this study showed that intersection layout, priority regulation,
as well as driver manoeuvres influenced the difficulty of passing
intersections. Intersection layout was the best predictor of variations in
workload. Three‐way intersections that only had a side‐street at the left‐hand
side of the driver turned out to be the easiest intersections to pass, whereas
four‐way intersections with dual carriageways were the most difficult to
manage. The abovementioned characteristics had the same effect on the
workload of functionally young and functionally old participants.
Functionally old participants had longer reaction times than functionally
young participants, and an increase in the complexity of the intersections to
pass led to longer reaction times for both functionally old and functionally
young drivers. However, the difference between the reaction times of these
age groups stayed the same (see Section 6.4.2).
The participants’ view of the intersection did not affect workload as
indicated by reaction times on a secondary task. However, this intersection
characteristic did affect another indicator of secondary task performance,
fraction missed. If buildings or trees obstructed the drivers’ view of the
intersection, drivers reacted to more stimuli than when their view of the
intersection was not restricted. This may indicate that it is more difficult to
pass intersections of which drivers have a good view while approaching it
than it is to pass intersections at which buildings and/or trees obstruct the
drivers’ view of the intersection. However, as the participants’ view of the
intersection only affected fraction missed and not reaction time, the higher
fractions missed which were found for intersections that were better visible
may also have been the result of a larger amount of visual information.
Having the opportunity to also look at cars and signs that are situated at the
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