Are All Crosswalks Created Equal?

The simple answer: no. Not at all. Just like a doctor doesn’t prescribe stitches for a stomach ache, our SDOT traffic signal engineers don’t apply identical pedestrian treatments to all intersections. Seriously, all jokes aside, each intersection is unique, and therefore require different treatments depending a wide variety of factors. For example, is traffic flow heavy or light? Are the walkers mostly University students heading to classes throughout the day, or adults dashing to and from work? Even the environmental details surrounding the busiest times of day play a role in helping SDOT engineers determine the right crosswalk for any given intersection.  Oh, and in case you didn’t know, there are a few different kinds of crosswalks:

  1. All-way Walk
  2. All Walk
  3. Leading Pedestrian Intervals.

All Walk vs. All-Way Walk

That’s right, All Walk and All-way Walk should not be used interchangeably, because they are not one and the same.

Here’s the difference:

  • All Walks only service pedestrians in the typical crosswalks at the intersection. Example: Broadway E and E Denny Way near the Capitol Hill Station- straight across, no diagonal crossing here.
  • All-way Walks – thumbs up to crossing diagonally! Example: First Ave and Pike St outside the market
  • All-way Walks require a much longer signal length to implement.

At more complicated intersections, longer signal cycles don’t play well with others. Shorter signal cycles are more user friendly in locations with heavy pedestrian travel and side street traffic because they offer more opportunities for people to cross. Hooray!

Capitol Hill Case Study: Broadway E and E Olive Way vs. Broadway E and E Denny Way 

 

 

 

 

Pedestrians crossing at Broadway E and E Olive Way (Photo Credit: The Urbanist)

 

 

  • Both run a 70-second signal cycle
  • An All Walk at each intersection = 25 seconds of that 70 second cycle
  • An All-way Walk = 35 seconds of the 70 second cycle
  • Broadway/Olive is a complex intersection with lots of left turns and a heavy transit use on Olive
    • If there was an All Walk or an All-way Walk at Olive, here’s what one could expect:Scenario 1: Multiple blocks of gridlock in all directions because buses, bikes and cars would all be vying for the last 35 to 45 seconds of the signal cycle Scenario 2:Pedestrians arriving at the end of the walk cycle would wait 35 to 45 seconds until they had another turn to move in any direction
    • Instead, SDOT engineers decided to: Use a Leading Pedestrian Interval, which gives pedestrians a few extra seconds at the start of the walk cycle, making them more visible to turning traffic and still leaving about 65 seconds for other traffic

This prescribed crosswalk allows pedestrians who want to go caddy corner to have shorter wait times, because they can either walk north/south or east/west at almost all times of the cycle!

  • Broadway/Denny is much less complex since half of Denny is a One-way. Therefore  an All-Walk was placed at this intersection. Design modelling showed that the extra ten seconds of an All-way Walk would cause backups at the intersection and force an undesirably long signal cycle.

Who knew that ten tiny little seconds could have such a major impact on on traffic? Well, SDOT  traffic engineers knew, which just goes to show why crosswalks are not one size fits all.