Assisting the older driver - SWOV

Intersection design and the older driver
multiple or advance signs, as well as by placing signs in the driver’s field of
vision and using signs that are larger in size and have a higher level of retro
reflectivity (Staplin et al., 2001). To prevent wrong‐way driving these
recommendations are particularly relevant for signs indicating one‐way
roads and ‘no entry’. However, the same applies to traffic signs indicating
stop‐and yield‐controlled intersections, since crashes resulting from failure to
yield are also overrepresented among crashes involving at‐fault drivers of
the age of 75 and older (Aizenberg & McKenzie, 1997; Davidse, 2000; Zhang
et al., 1998). More important, Council & Zegeer (1992, cited in Staplin, Lococo
& Byington, 1998) found that “young‐old” drivers (65‐74 years old) and “oldold”
drivers (75 years and older) more frequently failed to yield and more
often disregarded the stop‐sign than a comparison group did (30‐50 years
old).
Road marking and delineation of median islands and other discontinuities
Road markings help the driver to maintain the correct lane position and give
him a preview of the course of the road ahead. Because of their decreased
contrast sensitivity (and their extended perception‐reaction time) older
drivers need a higher contrast between pavement markings and carriageway
to be able to see the markings and have still enough time to act upon them
(Staplin et al., 2001). The same applies to the delineation of discontinuities,
such as curbs of traffic islands and medians. The results of several focus
group discussions have indicated that older adults have difficulties in seeing
these discontinuities, resulting in a possibility of running over them
(Benekohal et al., 1992; Staplin, Lococo & Sim, 1990; Staplin et al., 1997).
Studies in the United States have indicated that driver performance –
measured by the probability of exceeding lane limits – was optimized when
the perceived brightness contrast between pavement markings and the
carriageway was 2.0 (Allen, O’Hanlon & McRuer, 1977; Blackwell & Taylor,
1969). This means that pavement markings should be at least three times as
bright as the carriageway. However, these studies were not specifically
focused on the accommodation of older drivers. Another study compared the
performance of the top 5 percent of 25‐year‐olds (the best performing
younger drivers) with the bottom 5 percent of 75‐year‐olds (the worst
performing older drivers). Taking the contrast requirements for the latter
group into account, Staplin et al. (2001) recommend a minimum in‐service
contrast level of 3.0 between the painted edge of the carriageway and the
road surface for intersections without overhead lighting. For intersections
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