Traffic Safety is a Matter of Design

originally published on the Mary Black Foundation blog, December 3, 2010

Commuting by bicycle allows me a different perspective on streets and street life than motorized users have.  Slowing down provides part of the perspective, as I’m not speeding by the sculptures, the fountains, or the other non-motorized users of the street.  I see and feel the contrast between the often hostile, high-speed, quick actions of the automobile driver and the slower responses and more deliberate actions of the cyclist. 

I also note how these contrasts differ depending on the setting.  Riding on Main Street through the central business district is a whole other experience than riding on the four-lane East or West Main Street sections.  Traffic moves more slowly downtown, drivers seem less rushed, and maybe because I can go the speed limit on my bike, I feel much safer.

Pay attention next time you drive our busiest roads to the number of cars changing lanes in front of you, turning left either in front of you or across on-coming traffic, turning right or left out of businesses, running red or yellow lights, or stopping fully across the crosswalks at a red light.  You’ll notice several near accidents; as a driver you focus fully on the other cars, and may hardly notice the guy on the bike, or the woman walking on the sidewalk.

The two settings feel safe or not because of the design of the road.  Though driver behavior does come into play, most of the behavior is related to the ways cars and trucks have to move in certain contexts.  Road designs tell us how to drive on a certain stretch of roadway.   Main Street through downtown slows down not just because the speed limit drops, but because the roadway changes. 

I recently read a report by the US Department of Transportation that studied the effects of raising or lowering the speed limit on certain road sections.  The study found that traffic will move at the rate of speed deemed reasonable for the roadway, not that mandated by speed limits.  Lowering speed limits alone may do nothing to lower travel speeds.

East Main Street from Dean Street to Pine Street is a great example of this phenomenon:  the marked speed limit is 25 miles per hour, but on the road, which looks like a drag strip, speeds have exceeded 60 miles an hour according to Spartanburg Public Safety officers.  Try to drive 25 next time you’re on that section.  The roadway simply tells us to drive faster than the marked speed limit. 

If we really want traffic to slow down, we need to give the drivers signals to do so:  narrowing the width and reducing the number of travel lanes, and adding landscaping all have significant traffic calming effects.  Well marked or raised crosswalks alert drivers to pedestrian activity.  Besides giving cyclists a safe travel lane, bike lanes also tell drivers where to drive.  Lowering the speed limit without making any other physical changes puts the onus on public safety to enforce the law that isn’t necessarily reasonable for the road conditions.