Washington thru Traffic Engineer Eyes

Because this synopsis of the Washington Avenue traffic study gets a little wonky, here’s the executive summary: 

 

Hennepin County just released a report that shows it could reconstruct Washington Avenue, eliminate two lanes in the process, and still reduce congestion by optimizing the signal timing.  The great news from this study is that it substantially weakens (or even eliminates) the short-term congestion-based argument against removing the lanes.  

 

Before I dive into the long version, I want to insert the perspective of the Minneapolis Bicycle Coalition.  We disagree with Hennepin County that questionable assumptions about future traffic growth justify six lanes rather than five lanes. We also disagree with the policy decision that livability of the 5,000 current neighborhood residents living within two blocks of this project is less important than 90-180 seconds of travel time caused by the additional year-2035 commuters who may or may not ever appear on Washington.

 

 

Now for the long version, with more detail and background – wonky enough I had to get some assistance writing this up:

 

Hennepin County is planning to completely reconstruct Washington Avenue between 5th Avenue and Hennepin Avenue, and is also studying potential improvements in the Mill District between the 35W ramps and 5th Avenue.  To help inform the designs for the new street, Hennepin County commissioned Alliant Engineering, Inc. to complete the “Washington Avenue Traffic Operation Analysis,” which was made available to the public via the County’s website last week.  

 

Some of the assumptions in the report have been questioned, as you can read in Brendon Slotterback’s blog post at streets.mn. 

 

With all due respect to Brendon, I take a different view Alliant Engineering’s work.  I actually love their Traffic Operation Analysis.  

 

I love it, because it offers careful, honest, and precise analysis of the traffic conditions on Washington.  Some may argue that the report takes a very narrow view of the world.  They might say it excludes the things that downtown residents and employees care most about, like a consistently compelling downtown experience, leading the nation in transportation options, creating green infrastructure, showcasing the riverfront, or forging connections to the University of Minnesota (to plagiarize freely from the Downtown Council’s 2025 plan).

 

They might also say the traffic analysis fails to adequately consider the Downtown Council’s vision for the greening of downtown. 

 

Some critics would say that traffic engineers get paid to view the world through a straw.  I would argue that this is not a shortcoming, because the fact is that most professionals, whatever their profession, get paid to view the world through their particular straws.  So rather than criticizing this report, I have a different proposal.  

 

Let’s join the traffic engineers for a moment, look through their straw with them, and see what we can learn from their highly focused analysis.  

 

The main point of the report is to compare the performance of a 6-lane street (described in the report as 5 lanes with center turn lanes) to the performance of a potential 5-lane street (described in the report as 4 lanes with center turn lanes).  The report includes several variations on each layout that adjust the use of right turn lanes, but these variations are sideshows to the reports main event, which is addressing the question of whether 6 lanes are needed to adequately move traffic on Washington.  The report focuses on the afternoon rush hour in particular, because that is the period of highest congestion along Washington.

 

What the traffic study shows is that even if you completely ignore the tangible, economic benefits of greening downtown and creating a world-class, attractive and people-friendly corridor, it still makes sense to build Washington Avenue as a 5-lane street, based on today’s traffic counts.  Why?  Because with optimized traffic signals, 5 lanes will have less congestion than the current condition with 7 lanes.

 

The first reaction from some people who hear about reducing the number of lanes on Washington is “are you crazy, the traffic barely moves with 7 lanes, how on earth could it be better with 5 lanes?”  The answer is that the number of lanes is not the only factor in moving traffic.  The coordination of signal timing along a street is equally important.  A ‘green wave’ of well-timed signals can move lots of cars through a single traffic lane, while a less coordinated sequence of green lights causes delay and frustration, even with a smaller number of vehicles.  

 

On precisely this point, the report provides a useful comparison by showing how many vehicles can be transported, per lane, when signals are optimized.  During the afternoon rush hour, 3rd Street, which has 3 west-bound lanes, moves more than 2,000 vehicles through its busiest blocks (Figure 6, Page 16).  Washington, despite having an equal number of west-bound lanes as 3rd Street, never moves more than 1,400 west-bound vehicles, and nearly all blocks carry fewer than 1,100 vehicles (Figure 6, Page 15).  So with good signal timing, 3rd Street moves roughly 670 vehicles per lane during rush hour, while Washington only moves roughly 370 vehicles per lane.

 

The point is that with good signal timing, a lane of traffic in the downtown grid can move 670 vehicles in an hour.  So, by reducing Washington to 2 lanes in each direction, and improving the signal timing, Washington could have increased capacity, and become much less frustrating for people commuting by car or bus.  But you don’t have to take my word for it, the traffic analysis states clearly that “a 4-lane cross-section…  is expected to generally operate acceptably under existing year 2011 traffic volumes and optimized signal timing.“ (Page 22) 

 

The diagrams that demonstrate this conclusion are striking.  Using traffic simulation software, Alliant Engineering projected the level of congestion that would result from each scenario, on a block-by-block basis, and compared that to the current condition.  Figure 1 (Page 47, and top in the graphic below) shows the baseline ‘current condition.’  All of the blocks between Hennepin and 35W have at best moderate congestion (yellow), with most of the blocks showing congestion (red).  Figure 2, Scenario 3 (Page 48, and bottom in the graphic below) shows how traffic would move after a reconstruction that eliminates one lane in each direction.  Notice the number of blocks that turn from red into yellow or green (which indicates smooth traffic flow)?  Comparing Figure 1 with Figure 2, it’s clear that improved signal timing would make a big impact on this corridor.  Washington Avenue after the reconstruction would be much improved for motorized commuters, even with two lanes removed.  

So, if a 5-lane Washington Avenue will move traffic acceptably, why is there hesitation from the County on this?  Why isn’t the County simply proceeding to design the best of both worlds – a street that improves conditions for commuters while maximizing livability for local neighbors at the same time?  Why does the study recommend on page 38 that the County maintain 3 through lanes in the west-bound direction, and maintain a 6-lane road?  

 

Because of 2035.  As directed by Hennepin County, the study presumes (and full credit to the study’s authors for their careful and transparent documentation of their assumptions) that every year, traffic counts on much of Washington will increase by 0.5%.  (And as Brendon pointed out in his post, that assumption doesn’t match current trends, or even current declining traffic count trends on Washington Avenue, shown in this chart.)

 

 

This increase, if it occurs, will result in roughly 13% more vehicles by 2035.  The study then builds from this assumption a model of traffic flows after this 13% increase.  Many conclusions are based on this 2035 traffic forecast.  For example, by 2035, on the blocks west of 5th Avenue, there will be an average of 1,300 westbound vehicles per day on Washington during the afternoon rush hour.  This increased traffic will cause increased delay, which Alliant Engineering has quantified, down to the nearest second, shown in the chart on page 30.  So, maintaining 3 west-bound lanes will result in 2035 travel times across Washington Avenue of 5 minutes, 28 seconds.  Reducing the width to 2 west-bound lanes will result in 2035 travel times across Washington Avenue that range from 7 minutes, 4 seconds (Scenario 6a, which includes right turn lanes) to as much as 8 minutes, 30 seconds (Scenario 9, which removes some of the right turn lanes).  IF traffic counts increase 0.5% per year.  

 

In simpler English, if 3 travel-lanes aren’t maintained in the west-bound direction, 2035 travel times from 35W to Hennepin Avenue will increase by 90 – 180 seconds, for an average of roughly 1,300 vehicles during the afternoon commute.

 

This is the brilliance of the Alliant report: it states, with unselfconscious ‘looking at the world through a straw’ honesty, that 1.5 - 3 minutes of time during the afternoon commute of 1,300 people in 2035 is more important than creating a world-class, game-changing new Washington Avenue that would improve livability for thousands of downtown residents and employees, starting in 2014.

 

 

To put the impact on those 1,300 2035 commuters into perspective, let’s take a moment to count the number of downtown residents who would benefit from a greener, 4-lane Washington Avenue starting in 2014.  Let’s pretend, for the sake of discussion, that the only residents who are impacted by Washington are the ones who live within 2 blocks of the section studied by Alliant.  Let’s only count apartments and condos that are already built or under construction, and ignore development sites with pending proposals.  Also, for the sake of a rough estimate, let’s say that every apartment and condo has an average of 1.4 occupants.  

 

So here’s a list of residential buildings with the estimated number of occupants.

 

Velo Apartments	131
222 Hennepin	372
River Towers	641
Churchill	468
Rivergate	350
The Carlyle	324
RiverWest Condos	540
The Whitney	42
Metropolitan Lofts	29
North Star Lofts	34
Stone Arch Lofts	47
Washburn Lofts	29
Humboldt Lofts	47
Mill District City Apartments	228
Park Avenue Lofts	48
Saint Anthony Mills Apartments	121
Zenith Condos	83
Bridgewater Condos	373
StoneBridge Condos	213
Emanuel Apartments	131
American Trio Lofts	118
The Crossings	393
607 Washington	40
The Atrium	389

 

The total number of residents within a 2-block radius of the study area is roughly 5,000.  

 

On one side of the scale are thousands of residents, plus thousands of visitors and thousands of employees, who would start benefitting in 2014. On the other side is 60-180 seconds for 1,300 commuters in 2035.  The holistic public policy calculus, and the political calculus, should be glaringly obvious by now.  

 

The commissioners at Hennepin County, especially Peter McLaughlin, have the chance to deliver a legacy project to Downtown Minneapolis.  The time is now for residents of Downtown to make it clear that the greening and livability of Washington Avenue matters to thousands of residents who deserve at least as much respect as a commuter in 2035.  Please show up to the meeting on May 14.  And if you can’t make it to the meeting, email or call (612-348-7844) Peter McLaughlin to let him know what a greener Washington would mean to you.