Assisting the older driver - SWOV

Assisting the older driver
intersection characteristics and manoeuvres, intersections were also grouped
together according to the combination of characteristics that pertained to
them, and the manoeuvre the driver had to carry out. For grouping
purposes, intersections and the necessary manoeuvres were first scored on
whether participants had to: 1) pay attention to other traffic participants
before passing the intersection (yes/no), 2) think about what is left and right
(yes/no), 3) turn the steering wheel (yes/no), and 4) turn in front of a traffic
stream (0‐3 streams). Total scores ranged from zero to six. Intersections were
then grouped according to their total score. In order of difficulty (from very
easy to very difficult), the resulting categories were (nint = number of
intersections):
• (IM1) Right of way (nint = 5)
• (IM2) Yield to approaching traffic on a 3‐way intersection while turning left ( ┤) (nint = 4)
• (IM3) Yield to approaching traffic on a 4‐way intersection while turning left (nint = 5)
• (IM4) Enter a roundabout (nint = 2)
• (IM5) Yield to traffic from the right while crossing an intersection (nint = 3)
• (IM6) Cross a major road or turn right onto it (nint = 3)
• (IM7) Turn left at a 3‐way intersection (┬) (nint = 3)
• (IM8) Turn left at a 4‐way intersection (nint = 3)
Again, mixed between‐within analysis of variance showed that functional
age significantly affected reaction time (F(2, 36) = 6.349; p = 0.004; η 2 = 0.261)
and fraction missed (F(2, 36)=5.630; p = 0.007; η 2 = 0.238). Post hoc Bonferroni
tests showed that functionally older participants had longer reaction times
than functionally younger and functionally middle‐aged participants (p =
0.004 and p = 0.037 respectively), and that their fractions missed were higher
than those of functionally younger participants (p = 0.006).
The combined intersection and manoeuvre characteristics (IM) also
significantly affected reaction time and fraction missed (see Table 6.6).
However, the proportion of the variance in the dependent variables reaction
time and fraction missed that can be attributed to this newly created variable
(η 2 = 0.264 and η 2 = 0.228 respectively) is lower than it was for the previously
described variable of intersection layout (η 2 = 0.355 and η 2 = 0.321
respectively). Moreover, results of the post hoc Bonferroni tests for the latter
variable were more consistent with the expected difficulty of various
intersection layouts (see third column of Table 6.5) than results of the post hoc
Bonferroni tests for the combined intersection and manoeuvre characteristics
were with their expected order. As a result, reaction times and fractions
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