Assisting the older driver - SWOV

Effects of intersection design on workload and driving performance
Crashes in which older drivers are involved probably occur in traffic
situations that are more difficult to handle. An essential element that makes
these situations more difficult may be the fact that they trigger the wrong
mental schemata. If a situation looks similar to a well‐known situation but in
fact is completely different and requires other actions for safely passing the
intersection, mental schemata will work counterproductive. They will lead to
the selection of inappropriate actions and will therefore make the task more
difficult instead of making it easier. It would be interesting to check this
assumption by evaluating the design of intersections at which many crashes
occur in which older drivers were involved. The question to be asked would
be whether there is something in the design of the intersection or in the
design of the approaching streets that triggers mental schemata that do not
fit the actual situation. The pilot study that was reported in Section 5.2 has
shown that such an exercise asks for a well‐organized examination based on
a structured list of elements that may trigger mental schemata. As a matter of
fact, the examination could be considered to be the psychological version of a
black‐spot analysis or its proactive counterpart the road safety audit.
6.4.3. Limitations
There are a number of limitations of this study which should be mentioned.
First, the proportion of unsafe driver decisions may have been affected by
route instructions for surrounding traffic and the resulting speed reductions
of these vehicles (see Section 6.4.1).
Second, the secondary task that was used for measuring workload could
have measured more than that. One of the benefits of the introduction of a
secondary task is that it indicates whether task difficulty indeed differed
between various experimental conditions (see e.g., Teasdale, Cantin,
Desroches, Blouin & Simoneau (2004), and Van Winsum, Martens & Herland
(1999) for similar results on the effects of road design on secondary task
performance). However, a secondary task can also distort the results of an
experiment. The addition of a secondary task can, for example, influence the
primary task (Kantowitz & Simsek, 2001). In the present study, this could
have occurred as a result of visual distraction or interference with regular
driving‐related scanning behaviour and as a result of interference with
steering behaviour. To prevent the former – participants paying too much
attention to the area in which stimuli were going to be presented – we
instructed participants to consider the task of driving as the most important
one. If they saw one of the stimuli on the screen they should press the button,
but otherwise they should pay attention to the traffic situation just the way
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