Literature consistently finds a higher level of safety
at roundabouts compared to other types of
intersections. However, some studies indicate that
there is still a lack of safety on rural roundabouts.
Particularly high approaching speeds combined
with insufficient perceptibility of roundabouts can
cause accidents when drivers lose control of their
vehicle (especially during nighttime).
The goal of this study is to analyze correlates of
safety at rural roundabouts in Germany and to
investigate opportunities to improve their safety.
The analysis of accident characteristics in data from
official statistics shows that 60% of all accidents
happen in twilight and at night time and that four
out of ten accidents are single-vehicle accidents.
Single-vehicle accidents have the highest severity
and usually end up on the central island of
roundabouts.
For detailed accident analysis of 109 roundabouts,
information on road design, signage, traffic volumes,
and accidents was collected for each approach.
Using generalized linear models, the following
effects of roundabout design on accident risk were
found:
• Approaches with a curvilinear alignment or a
chicane have significant lower accident rates
than approaches with straight alignment.
• Approaches with high angles of deflection have
higher accident rates than approaches with
moderate angles of deflection.
• Wide splitter islands with triangle shape provide
lower accident rates than narrow splitter islands
with straight curb.
4
Finally, observations of driving behavior and
photometric studies were conducted at more than
30 approaches of rural roundabouts. The influence
of approach alignment on speed behavior and the
shape of splitter islands on track behavior proved
the results obtained by the accident analysis.
Photometric studies showed that the usage of
retroreflective elements on the curb of the splitter
island increase the visibility of rural roundabouts
during the night.