Crossing an Intersection on
Foot—Improved Safety Equals Constraining Vehicle Speeds
When it comes to improving
safety at busy urban intersections, improving safe movement for those on foot
requires some physical constraint on vehicle speeds.
There exists a common belief
that placing signals at an intersection improves pedestrian safety. That may or may not be the case. But generally signals offer little difference
in pedestrian injury rates compared to sign control. Swedish highway authorities use the same
formula to measure walker safety whether the intersection has stop signs or a
traffic signal.
The one overwhelming truth
about intersections is that frequency and severity of pedestrian injuries
depend on prevailing vehicle speeds. And
the best way to constrain speeds of vehicles comes in the form of traffic
calming—speed humps/bumps, median diverters which provide a center street
refuge as well as forcing a slight divergence of the straight line vehicle
travel which reduces vehicles speeds, and the roundabout.
Consider the “race through
the stale green” by a vehicle approaching a signal, violating right turn on
red, and a vehicle blowing through a red signal—and the connection between
speed and walker crash vulnerability at signals becomes clear.
The roundabout does a lot of
things to improve walker safety—such as, providing a median refuge, moving
those crossing from several vehicle conflicts, etc.—but most importantly the
roundabout slows vehicles. There now
exists plenty of research and U.S. experience to confirm the traffic calming
effect of the roundabout and improved walk mode safety. The fact there are about 4,000 roundabouts in
the U.S. and Canada built since the first in 1990 without a pedestrian fatality
should be enough to convince anyone of the safety provided to those who walk. Urban Melbourne with 4,000 roundabouts
recorded zero fatalities in one five year period—Burlington recorded two
fatalities at 75 signalized intersections in just 15 years! (This does not include the fatality just
across the border in So Burlington at the Sheraton/Stables crosswalk last
September.) France with its 33,000-plus
roundabouts offers a similar indication of walk mode safety—one pedestrian
fatality per 15,000 roundabouts per year.
The traffic calming effect of a roundabout extends outward one to two
blocks distant.
For all of us the first
criterion to be considered when investments are proposed at intersections
supposed to benefit walk mode safety must be:
does that investment reduce vehicles speeds? Any answer of “no” to that question must give
one pause as to why that investment is necessary—and, more importantly why not
also include in that project traffic calming which forces vehicle speed downward? Both Alberta and British Columbia ministries
of transport adopted a simple rule for intersections a few years ago—if something
more than two-way stop control is required the roundabout is the first choice.
Slowing vehicle speeds does
not mean greater travel time for the car.
A study of over 50 roundabout corridors in the U.S. found little
change—some slightly longer times, some slightly slower times—for through
travel. Reduced wait times at signals
compensated for the lower prevailing speeds along the roundabout corridor
compared to a signalized corridor.
So, when examining
intersection investments to improve walker safety the first criterion to be
addressed is: are cars speeds reduced through physical constraint?
