Assisting the older driver - SWOV

Assisting the older driver
place at an intersection in the indicated period of 10 years for the intersection
to be considered for inclusion in this study. The actual inclusion in this study
depended on the percentage of crashes in which older drivers were involved.
As this study was aimed at determining road design elements that raise the
task difficulty of passing an intersection for older drivers, thus leading to an
increased risk of errors and crashes caused by older drivers, the focus was on
the age of the first registered collision partner. This collision partner often
turns out to be the legally responsible one (see Appendix A). For every
intersection in the province of South Holland, two numbers were calculated:
1) The total number of crashes in which the first collision partner was a car
driver, and 2) the number of crashes in which the first collision partner was
aged 65 or above. If the ratio between the latter and the former was 0.30 or
higher, the intersection was included in the group of intersections called
Intold. If none of the first collision partners was 65 or older, the intersection
was included in the group of intersections called Intyoung. To avoid differences
between these two groups of intersections that are merely related to
differences in exposure, only those intersections were included in Intyoung that
had a comparable number of crashes in the period 1990‐2000 as those which
were included in Intold.
The total number of crashes that took place at the selected intersections
varied from 11 through 20. Intersections with relatively many crashes were
not selected, as none of these intersections could be assigned to Intold. Hence,
the intersections included in Intyoung may not be representative for all
intersections with no crashes involving older drivers. In addition, note that in
the rest of this section older drivers are those aged 65 and above. It would
have been preferable to use the age limit of 75 to assign intersections to either
Intold or Intyoung. However, it turned out that the use of the latter age limit
would have resulted in a selection of intersections that was too small to be
able to make any comparisons.
Data collection
To compare the two groups of selected intersections, several characteristics
of each of the intersections were gathered during visits on the spot. Pictures
were taken from each of the intersecting streets (from the perspective of a
driver approaching the intersection, both at 50 m and 10 m before the
intersection), and some general characteristics of the traffic flow were
recorded manually (between 9:15 am and 15:15 pm). Back in the office, the
information available from the pictures was coded into variables. These
variables were considered to describe the factors that were expected to
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