13th & Arapahoe Underpass Comments


This city is accepting public comment on the 13th & Arapahoe underpass project. For more information, see the current plans and the project website.  Below are Community Cycles’ comments.

Thank you for all your work to date on the 13th & Arapahoe Underpass project; this critical junction in Boulder’s bicycle and pedestrian network has numerous operational issues today and it looks like the proposed alternatives solve many of these. However, we believe that a couple of tweaks are necessary for this project to serve all modes safely and comfortably.

First of all, we believe the focus on the choice between a widened vs a new underpass is misplaced.  Both alternatives appear to solve the ADA grade issues, the sightline/visibility issues and the flooding issues.  As far as travel paths and desire lines are concerned, we can discern no significant differences between the two underpass options, and as such, we don’t think that this choice matters much to people travelling through this junction.  The other elements of this project (the at-grade crossing, connections to the Broadway path, etc.) matter much more and should thus dictate which underpass option is selected.

Second, we am a little concerned that the way in which the bike/ped user data is presented is diluting the importance of the N-S connection.  While we recognize that 13th St has three options for travel (the west side MUP, the road, and the east side sidewalk), splitting the numbers into these three components appears to make this node look less important than the E-W connection along the Creek Path.

Third, we would urge you to continue to focus on the N-S connection (Broadway path to 13th St).  As mentioned above, both underpass options appear to do a phenomenal job of solving all issues currently faced by E-W Creek Path users.  The N-S connection however appears to still be in jeopardy.  The high bridge option in my diagram (I believe referred to as the South Path Connection 2/ South Connection Option 2) is essential to creating a high-quality N-S connection.  This bridge, which would route N-S users over (and grade-separated from) the E-W path users would directly match the N-S desire line and provide a much more convenient route for the N-S movement.  To understand the benefits of grade-separating the busiest N-S bike route in the city from the busiest E-W bike route in the city, compare the Broadway/College underpass to the Broadway/Euclid underpass.  At Broadway/College, the N-S users and the E-W users meet at-grade.  The result is chaotic, congested, and dangerous.  At Broadway/Euclid, where the N-S path is above and grade separated from the E-W underpass users, none of these issues are present.

It is our guess that the high bridge option requires a longer span than the low bridge option (connecting the Broadway path to the Boulder Creek path directly).  This means the high bridge will require the City to purchase a new physical bridge.  If the low-bridge option could re-use the existing bridge, we would suggest that the City do both options.  The low bridge option facilitates easier movement between the Broadway path and the Boulder Creek path than not having it.  If it is either-or, however, the high bridge option should be prioritized to facilitate a more direct N-S route.

Fourth, we are happy to see that the City is considering new options for the at-grade crossing.  The existing crossing is a dangerous and inconvenient mess for bicyclists and pedestrians.  Motorists frequently blow through this intersection without yielding.  It is impossible for motorists to discern which way a SB bike is headed until the bicyclist literally puts their wheel in the intersection.  If a NB bike and SB bike enter the intersection at the same time, the result is a game of chicken to figure out who is going to go where (around the median refuge, on the sidewalk, etc.).  If a bike and pedestrian enter the intersection at the same time the whole maneuver falls apart- bikes often eschew the crosswalk while the pedestrian sets the screen.  Crossing Option 1, which looks very similar to the existing configuration, does not address any of these concerns.  Crossing Option 2, the z-crossing, would exacerbate these concerns by further congesting bikes and pedestrians in the mid-block refuge.  Crossing Options 3 & 4 solve almost all of these concerns (we especially like raising the whole intersection, and would encourage the City to look at Portland’s “crossbikes”), but they are missing one absolutely critical detail.  (For the record, we think it would be safer to omit the EB Left Turn lane to shorten the crossing distance, but this is ultimately less important than the last piece which is currently omitted.)

Most importantly for the at-grade crossing, SB bikes need to enter the intersection in the direction that they will be crossing.  I cannot overstate how critical this is.  Currently, the way that the intersection requires SB bikes to first head east on the sidewalk to then head south in the crosswalk means that motorists on Arapahoe have to guess that an EB bike is actually going to turn and head south. There is a simple fix to this issue, and the City has already done it in reverse at 13th & Canyon.  The MUP needs to “bend in” to 13th St (the orange line drawn on the diagram below) so that SB bikes enter the intersection already facing south.  The opening for 13th should be about 17 ft wide: 6 ft for SB bikes and 11 ft for NB cars/bikes and divided with a double yellow behind the E-W crosswalk.  This bend-in could also accommodate NB bikes that wish to merge onto the path instead of using the street.  On our diagram, this critical change would consume one parking space but would completely solve the current oversight of how SB bikes use this intersection.

Again, thank you for all of your work on this project; we are eagerly awaiting its opening date and will gladly suffer through the construction phase.  We would be happy to discuss any of these ideas in more detail if that would be helpful.