Knowledge CentreTechnical Resources SearchConference PapersDesign Consistency and Multi-modal Safety in Urban Areas

Design Consistency and Multi-modal Safety in Urban Areas


An important component of road safety is the compatibility between intended operations of a
facility and how drivers actually interpret and react to in-field geometric and traffic control
characteristics. Individual design elements may meet or exceed minimum standards, but safety
issues may still exist if the geometric characteristics are not fully consistent with signage and
markings. At intersections in urban areas, safety issues can be compounded by impacting not
only motor vehicle safety but also influencing the safety of pedestrians and cyclists.
Specific issues can arise when turning geometry is not fully compatible with the traffic control
scheme. For example, a channelized right turn that has yield control, but is otherwise consistent
in geometric design with an added merge lane (due to, for example, a large turning radius), can
result in conflicts due to variable driver expectations, with some drivers braking (as per the yield
control) while others accelerate to merge at speed, which can create speed differentials and an
increase in rear end and merging collisions. Issues can also arise where the safe travel speed
on an urban roadway alignment does not align with driver expectation.
This paper identifies common issues that can result in conflicts and collisions between motorists
in urban areas due to compatibility issues with respect to turn movements as well as roadway
approaches and alignments. Case study examples from Alberta and British Columbia are
presented, where the safety issue is identified (for vehicular as well as non-motorized travel
modes), the reasons (as possible) that the compatibility issue may exist in the first place, along
with mitigation options that can be considered (while highlighting potential benefits of those
improvements). Finally, conclusions and lessons learned are summarized.

Conference Paper Details

Session title:
Geometric Design - Lessons Learned: Linkages Between Design Standards and Road Safety
Jacobson, M.
Baumgartner, T.
Geometric design