Posts about Skybridges

But the difficult part is the array of constraints presented by the crowded, urban space in Bethesda at Wisconsin Avenue.

Bridging the gap

A trail bridge with long ramps on either end will not fit into the space available along Bethesda Avenue and Willow Street without blocking critical business access and parking structure driveway entrances. And that's not feasible unless the county is willing to purchase the affected properties.

A conceptual bridge alignment. Click to enlarge.

The aerial map above shows the approximate length of the ramps for a trail bridge over Wisconsin Avenue that would be needed to meet ADA requirements.

A ramp up Bethesda Avenue must elevate the trail by approx. 18 feet above Wisconsin Avenue to allow clearance for traffic below and space for bridge deck supporting structure. Bethesda Avenue rises from Woodmont Avenue to Wisconsin Avenue and the bridge ramp must "chase the grade", adding another approx. 10′ to the total elevation gain needed on the ramp. If we assume a 5% ramp grade, then we will need a ramp that is 560 feet long on Bethesda Avenue.

We can shorten the ramp a little and still be ADA compliant by going up to a 7% grade that has flats at regular intervals. But even so the ramp will still be too long to avoid blocking driveways on either side of Bethesda Avenue.

Any ramp over several hundred feet long on Bethesda Avenue will block important driveway entrances, whether on the north or south side of the street. The problem is much the same for a ramp on the other side of Wisconsin Avenue at Willow Street. A ramp on Willow Street could be shorter, maybe a little less than 400′, since it would not be "chasing the grade". But it would still be much too long to avoid blocking critical driveway entrances on either side of Willow Street.

Switchback ramps or spiral ramps are shorter than linear ramps, but their footprints are at least twice as wide—there is no place that can accommodate the wide footprint of either a switchback or spiral in this area. And the question arises: "How many trail users will want to use such long, steep ramps if they can cross at-grade at a light?"

Can we find another location for the bridge and ramps?

If we explore other locations for a Wisconsin Avenue bridge crossing, we will get the same result: long ramps will create unacceptible blockages of driveways and business entrances. Elevated crossings at Elm Street, Miller Avenue, or Leland Street will create unacceptible blockages by the ramps on both sides of Wisconsin Avenue, and the routing of the trail on the east side of Wisconsin Avenue becomes very problematic for these alternate crossing locations. The "chasing the grade" problem is even more severe on Elm Street than it is on Bethesda Avenue.

An alternate approach is to consider "going aerial" for a longer distance than just on a bridge, so the ramps can be some distance away from the constraints near Wisconsin Ave. One obvious areal route would be to have a ramp at the Bethesda Trailhead adjacent to Ourisman Honda, go on aerial structure across the Bethesda Ave./Woodmont Ave. intersection, up Bethesda Ave., across Wisconsin Ave., and up Willow Street and then come down another ramp at Elm Street Park.

But the ramp at the Bethesda Trailhead would have to begin about 400′ south of Bethesda Avenue and very near the trail rest plaza to gain the elevation needed to clear Bethesda Avenue. The width of the ramp, at least 14′, would likely preclude also having a full width surface trail alongside the ramp. The local trail access to Bethesda Row along the trail right-of-way would be greatly compromised.

A long aerial structure would be very visually intrusive to the rest stop, Bethesda Row, the future Woodmont Plaza, all of Bethesda Avenue and Willow Street, and to Elm Street Park. Access to the Bethesda street grid and downtown destinations would be limited. If the only goal is to separate trail users from the Bethesda street grid, it might be better to reroute the CCT to completely bypass downtown Bethesda. But these approaches will not serve the many trail users who want good access to downtown Bethesda destinations.

Would a trail tunnel under Wisconsin Avenue fit any better?

Yes, a new trail tunnel would have much less impact on the Bethesda streetscape than would any trail bridge.

Conceptual tunnel alignment in Bethesda. Click to enlarge.

The conceptual sketch above shows the approximate location of portals (shown as red markers) into a new tunnel under Wisconsin Avenue. The aproximate lengths of the down ramps, or cuts, needed to take the trail elevation down to enter the tunnel at the portals is also shown.

Note that the down ramp, or cut, needed on Bethesda Avenue is less than half the length that would be needed for an up ramp to a bridge. There are two reasons why this is so. First, the existing elevation change along Bethesda Avenue helps for a down ramp, instead of forcing us to "chase the grade" for an up ramp. Second, we don't need as much elevation difference between the street grade and the top of the tunnel as we needed for clearance for the bridge (only maybe 12′ vs. 16′). I estimate a down ramp as little as 200′ long might work on the Bethesda Avenue end of the tunnel. That could just fit on the north side of Bethesda Avenue without blocking any existing driveways.

The down ramp on the Willow Avenue end of the tunnel would be a little longer, since there is no help from an existing grade on that side, and it would be too long to fit along Willow Avenue without blocking a driveway. The most feasible location for that down ramp would be as shown in the sketch, along the east side of 47th Street at Elm Street Park. A ramp should ideally continue east along the north side of Willow Street at the Park to avoid the trail turn at the tunnel portal, but I estimate that block of Willow Street is too short for the down ramp to fit.

The tunnel path shown in the drawing is only notional and can shift slightly to better suite construction conditions, but I think any "cut and cover" tunnel will need at least one bend in it to avoid buildings. A deep bore tunnel could be straighter if it goes under buildings, but it would be prohibitively expensive.

A tunnel can fit. Does that make it good?

This tunnel will fit into the Bethesda streetscape much better than will any elevated structure. The obstructive ramps would be much shorter, and the visual intrusion would also be minimal. But the tunnel will not be attractive to many trail users, and the cost will be high.

This is a long tunnel, and will not resemble an underpass which has a much more open feeling. The tunnel will not be as wide or high as is the existing trail tunnel under the Air-Rights Building. It will have curves and turns that will limit the sight lines to be much shorter than in the existing trail tunnel.

Trail users will not be able to see what is ahead of them in the tunnel when they enter. The perception and the reality of safety will be much lower than we have experienced in the tunnel under the Air-Rights Building. Many trail users (including me) will likely prefer to stay on an enhanced surface route.

The existance of this tunnel will preclude having a full width trail on the surface route. The tunnel down ramp on Bethesda Avenue will need at least a 14′ width, and that will take most of the width available so that only a minimal width sidewalk (6-8′) can remain alongside for the surface route. Similarly a 14′ wide down ramp adjacent to Elm Street Park will take the "easy" space between 47th Street and Elm Steet Park. Taking another 14′+ to also have a full width surface trail will have an unacceptible impact on the park. Trail users wanting to take the surface route instead of using the tunnel will be severely impacted by the existance of the tunnel.

Construction of the cut-and-cover tunnel will require moving all utilities along its path—and there will be many of them along these streets. The disruption to traffic on Wisconsin Avenue during construction will be considerable, and construction incentives to minimize the time of this disruption will impact cost. I do not have the experience needed to estimate the tunnel costs, but it is a safe bet it will be high.

I believe a new trail tunnel under Bethesda Avenue will compare very poorly with the tunnel design that has been proposed for the trail with the Purple Line under the Air-Rights Building. It is a bad idea, largely because it will obstruct a full width, off-road trail on the surface route that many of us would choose to use instead of the tunnel.

What is the best way forward?

WABA has stated its position on the way forward in its Quick Release blog.

"…as advocates for the best possible trail and crossing, WABA asks that the county take steps to evaluate the importance of a grade-separated crossing, account for the importance of grade-separation to trail usage and safety by including an alternative grade-separated option, and clearly define the proposed enhancements that would be included in the on-street option that would make it more than a fallback cost-savings at the expense of trail users and to the detriment of the project."

I think there is little value in exploring an alternative grade-separated option much further. The many constraints of the Bethesda urban design space will make a new trail bridge not realistically feasible. The best likely new trail tunnel will be too unattractive to many trail users and will physically obstruct our best surface trail route.

Continuing to pursue an alternative grade-separated crossing will only take us to more dead ends. We should instead focus on getting the strongest possible commitment from the County that if a decision is taken to not keep the CCT in the tunnel under the Air-Rights Building, then the features recommended for the enhanced surface route in the Planning Board letter will be implemented. The most important of these enhancements is to provide a protected Wisconsin Avenue crosswalk by restricting motor vehicle turning movements.

With the commitment of the county, we can design a safe, direct connection for the CCT that is on-street. We should push for the best design possible as we focus on building a better trail for the future.

The Council has rejected the bridge before, but it keeps coming back up. The latest iteration arose because Council President Valerie Ervin, whose district includes the library, recently revived the idea.

Before the Council's hearing on the matter, Riemer asked for input. His Facebook followers came out strongly opposed. Here are a few of the comments:

• 
  Cavan Wilk I'm against it. It's a waste of money. Plus it would have the negative impact of removing pedestrians from Wayne Avenue, telling motorists to speed up. The presence of pedestrians tells motorists they're in a town environment and they need to watch for pedestrians.
• 
  Jill Curry Robbins *Another* one? When will this misguided idea die?

  The money would be better spent improving the intersection at Wayne and Fenton to improve safety for all pedestrians—handicapped and otherwise. This would benefit the entire neighborhood, and it would keep more traffic at street level, where it would benefit retail. This will be especially important with the ground-floor retail going in across Fenton from the library when the Baptist church's planned development is built.

  Someone has convinced countless business owners in Fenton Village that the bridge will benefit them, but I can't see how. As I understand things, it's in no way a true "bridge" across Wayne, but a connector from the parking garage directly into the library. Nobody's going to wander into an interesting Fenton Village shop, or be drawn into a restaurant by the smell of coffee or injera or roasting chicken, when they can zip straight from their car to the library and back again. ...

• 
  Seth Grimes I oppose the bridge based on cost and especially because it will discourage library visitors from patronizing local businesses before/after library visits. Please vote against!
• 
  Richard Potter Oh, please....People can't cross at the crosswalk? Fenton is not a six lane highway!
• 
  Robert Padgette Bad idea. Allow on street disabled parking in front of the library instead.
• 
  Andy Sullivan Anti-urban. Waste of money. Will turn the intersection into a freeway cloverleaf.

Fellow at-large Councilmember George Leventhal chimed in during the hearing:

• 
  George Leventhal Comments so far at the County Council's public hearing: 100 percent in favor of the bridge. Comments in response to Hans' facebook query: 100 percent against the bridge. What's going on?

A fascinating debate about the role of social media versus attending hearings in person then ensued:

• 
  George Leventhal http://www.thayeravenue.com/2011/02/15/save-the-date-march-8-2011-at-730/

  Here's a blog post from Thayeravenue.com urging people to attend the public hearing tonight but Thayeravenue himself didn't even attend the public hearing!

  How are elected officials supposed to know what the public thinks if the public doesn't show up at public hearings?

• 
  Robert Padgette George, we're at home watching the kids hoping those we elected to office do the right thing. We all know that those who show up at public hearings do not represent general public views. Social media offers an opportunity to hear from a broader audience. Kudos to Hans for embracing this medium.
• 
  Hans Riemer This is a very important conversation and I appreciate everyone's thoughts. I want to say that I don't think this is about people who testify versus people who don't, blog people versus real people, and so forth, and whose opinion really counts. Everyone's view is important, at least to me. George Leventhal has a point that the official process is for public record and it is important for people to participate on record. At the same time, I believe that my job as a council member is to seek out the views of people who are affected as best I can, and not just rely on hearing from people who come to me. Its a balancing act and there are always differing views in the community about this or any issue. And in the end, as elected representative, I have to do what I think is right after considering all of the information that I have received.
• 
  Andy Sullivan Public meetings are generally held at a time when it's all hands on deck in the Sullivan household, getting dinner on the table and tykes in the bed. I'm glad Hans is using all available forums to solicit input.
• 
  George Leventhal Yes, all input is good and I enjoy getting feedback over social media but we shouldn't discount the importance of actually participating in the process, which unfortunately sometimes requires going to City Hall (or in our case the County Council Office Building). But we take written testimony which is entered into the public record from those who aren't able to testify in person, too. Twitter and facebook, etc are informal; a hearing record is more of a formal document. Our decisions are informed by both and both are useful and important.
• 
  Hans Riemer Well, I do think that commenting on Facebook is participating, as is sending email to the council, making phone calls to council members, sending post cards, and everything else. I hope everyone will do everything that they can do to make their voice heard.
• 
  George Leventhal This exchange would be fascinating material for a PhD dissertation on the new media. I would point out that Hosni Mubarak was brought down when people who were communicating with each other on facebook actually left their homes and cafes and congregated in Tahrir Square. While I acknowledge the connection between social media and political action, I think there is more to political action than simply typing notes on the computer. There is the idea, there is the sharing of the idea, and then there is the carrying out of the idea. From concept to execution takes multiple steps. Sending each other messages is only one part of the spectrum.

This dynamic comes up in many areas where there are opportunities to participate in government but which require a substantial time investment. At many hearings, people can travel some distance and wait for hours just to speak for two minutes. To testify at the Virginia or Maryland state legislatures also can involve a long trip just to get to Richmond or Annapolis.

That burden means that those more committed will have louder voices. Sometimes that's a good thing, but it also tends to favor those who have fewer demands on their time. Retirees, for example, can more easily spend the time than parents of young children.

As a result, many boards tend to be comprised of individuals who either have a professional interest in the issue, or who have more than the average amount of free time. That means that for important boards like DC's HPRB or Zoning Commission, it's difficult to find candidates to represent different points of view. Even the WMATA Riders' Advisory Council is vastly skewed away from parents.

Social media can give people an opportunity to participate without having to take time off work or hire babysitters, but also favors those who have Internet-enabled mobile devices or jobs with computers. Clearly, there's no simple answer.

As for the bridge itself, the Council turned it down again. Leventhal introduced a motion to authorize the bridge, but his four fellow committee members, Craig Rice (district 2), Nancy Navarro (district 4), Marc Elrich (at-large), and Nancy Floreen (at-large), all declined to second the motion.

Thayer Avenue, which has now made some signs to oppose the bridge, also reports that Ervin could bring up the matter without a committee recommendation. But with four having already cast their lot against the bridge last week, opposition from Riemer himself or either of the other two, Roger Berliner and Phil Andrews, would keep it from moving forward.

It seems to be based on the recent Confessions of a Recovering Engineer, also from Strong Towns.

Lest you think this is gross parody, I had a conversation very similar to the first few exchanges in this video with a project manager in DDOT's IPMA about how much to round the corner of 18th and S, NW, and I've heard public statements that eerily resemble other parts from leaders of the Montgomery County DOT.

I find it surprising that few cyclists use the bridge. Perhaps more use it during commuting hours. My counts have been in the middle of the day.

Early problems with the bridge have been mostly resolved. The trash cans appear to be regularly emptied and the graffiti is almost all painted over. The biggest problem is that the stairwells are used by loiterers, presumably at night. (They were not there while I was there). They leave behind beverage containers (alcoholic and non) and the stench of urine.

For future designers, I might recommend a more open architecture that would allow visibility from all angles, as DDOT plans to do at Rhode Island Avenue Metro. The ramps, which are open, are nice and clean and feel safe. The stairwells, which are mostly closed in, have litter and feel a bit less comfortable—probably much more so at night.

All in all, this bridge is a worthwhile complement to the transportation infrastructure in the area. I use it myself, and find it to be quicker and safer than my previous alternatives. However, much more needs to be done. As with last year, the walking routes to and from the bridge are completely insufficient—essentially nonexistent. The crossings at Seven Corners itself need to be redesigned to accommodate pedestrians.

The busy crossing at Patrick Henry is still dangerous. And of course, the entire area could use a long-term strategic plan, so that opportunities to improve it are not missed as various development and redevelopment occurs in the area.

That sounds like some other 1950s-60s era ideas for "safety," like separating all pedestrians in skybridges that force them to walk out of their way to cross streets. Pedestrians tend to ignore overpasses, and likely would also ignore the "don't walk" signs. As Streetswiki points out, that eliminates the safety gain.

The Streetswiki article also notes that by stopping pedestrians from crossing when vehicles want to make turns, the Barnes Dance could move traffic more quickly. Therefore, like skybridges, a traditional Barnes Dance could end up adding driver convenience, not pedestrian convenience, while wearing the guise of a pedestrian improvement.

But DDOT isn't doing a traditional Barnes Dance. Instead, they're doing something that is definitely a boon to pedestrians. Pedestrians can now cross diagonally or orthogonally during the all-walk phase, but also cross orthogonally parallel to traffic.

On its own, that would hurt motor vehicle flow a great deal, so DDOT eliminated turns. That way, there aren't the pedestrian-vehicle conflicts that could hurt safety and also slow down drivers trying to go straight. Of course, this depends on driver compliance.

This is a good example of a policy that puts pedestrians first. However, it comes at some cost to traffic flow, if only to turns. At Wisconsin and M, there are lots of turns. In fact, DDOT is planning to add another turn from eastbound M onto northbound Wisconsin. And a lot of buses, including Circulators, turn from M to Wisconsin.

If a Georgetown Barnes Dance prohibits pedestrians from crossing during the phases where cars and buses are moving, it'll hurt pedestrians more than help, and many will just violate the laws anyway. If it allows pedestrians to go and also allows turns, it might gum up traffic more than we can accept.

The more important improvement in Georgetown is to put in priority bus lanes approaching the intersection, so that buses don't get stuck with long waits to turn. With the volume of buses there, they are moving far more people most of the time than all the other cars combined. The intersection should prioritize the more numerous and more space-efficient pedestrians and bus riders.

A Barnes Dance at 7th and H makes a lot of sense, since it has enormous pedestrian volumes due to the Metro station entrance and there are plenty of parallel streets for turning and through vehicles. But this applies to very few places in the city, perhaps a few other intersections right at downtown Metro stations. We should make all intersections safer for pedestrians. In most cases, that probably doesn't mean a Barnes Dance.

Looking across from the CVS to Ennals Avenue. Note the lack of even a crosswalk.
3. Create a block at Ennals Avenue. Currently, a motorist on Viers Mill Road has little way of knowing that there is a small cross street between Reedie Drive and University Boulevard. There isn't even a signed crosswalk between the Ennals Avenue sidewalk and the CVS across the street.

   On Friday, February 5th, I almost saw a car collision between two motorists because there are no markings to cross Viers Mill Road from the (suburban-style) CVS parking lot. The curb cut for the CVS parking lot aligns perfectly with Ennals Avenue.

   Plenty of crossings between strip malls and side streets have blinkers or traffic lights. This would be a reasonable place to put one in to make motorists aware of potential pedestrian and automobile crossings. Better notification of the crossings, along with the wider median and relocated bus stops, would all work together in providing pedestrian vitality. The increased street activity will tell motorists that it is time to slow down.

   
   View larger map.

4. Narrow the lanes. Current lane widths are built to suburban arterial guidelines. Narrowing them to 10 or 11 feet (except the one lane that must be 12 for delivery trucks) would cause motorists to slow down and drive more gently, causing fewer collisions. The narrower lane widths would be more consistent with an urban boulevard like Wisconsin Avenue in Bethesda.
   
   Most motorists currently ignore the bus lane.
5. Fully separate the bus lanes. The right lane on Viers Mill Road has "Bus Only" painted on it just south of University Boulevard. However, just like on 7th Street NW in DC, few personal vehicle operators heed or even notice the markings. Inexpensive rubber poles would explicitly separate the bus lane, similar to the bike lane on 15th Street between Massachusetts Avenue and U St.

   There is precedent for using the rubber poles in Wheaton. MCDOT used them on Reedie Drive across from Triangle Lane (in front of the Mid-County Services Building) to create a bulb-out so pedestrians have less asphalt to cross and motor vehicle operators are more aware of the crosswalk. (The MCDOT deseves credit for implementing this good idea.)

   CVS's curb cut could remain a place for automobiles to cross the bus lane. It will not add much danger because the bus lane will have much less traffic than an automobile lane and the buses will be stopping at the relocated bus stop right in front of the CVS curb cut/Ennals Avenue crosswalk. The separated bus lanes would be in effect between University Boulevard and Reedie Drive both northbound and southbound.

6. Improve the crosswalk across Viers Mill Road on the south side of Reedie Drive. Pedestrian bridges suck for pedestrians. It's that simple. They're a metaphorical middle finger to them. They're always underused, whether it's in Seven Corners, Hyattsville, or proposed at the Silver Spring library.

   The pedestrian bridge across Viers Mill Road between Reedie Drive and Georgia Avenue is one of the less offensive examples of its kind because it at least provides a convenient route the the Metro for commuters who park in the upper levels of the Metro garage. Also, when a shopper gets off the Metro, the pedestrian bridge is the most obvious path to the mall.

   However, the reverse is not true. Depending on which exit a transit-oriented customer uses to leave the mall, crossing Viers Mill Road at Reedie Drive could be more convenient. The businesses along the eastern side of Viers Mill Road would love the increased foot traffic. Many pedestrians might make a new discovery such as Chuck Levin's Washington Music Center.

   Regardless, the increased foot traffic on the sidewalks and crossing the street will further tell motorists that they are on an urban boulevard and to drive accordingly. I personally use this crossing when I walk to the mall from my residence, too.

The upcoming 2010/11 Sector Plan will lay the framework for Wheaton to better use its existing walkable urban infrastructure and achieve its potential as an economic and social center of place. In order to facilitate this important process, all the infrastructure must be arranged to facilitate this positive growth. With a few small (low-cost) changes, Viers Mill Road between University Boulevard and Georgia Avenue can better serve the town that exists partly because of its historic proximity to the road.

In his letter to the County Council this summer (large PDF), Leggett insisted that "accessibility and sustainability" drove his recommendation:

The primary rationale is not one solely of safety; it is primarily one of accessibility and sustainability. The use of the existing underutilized parking garage is a "green" decision which saves the use of materials and taxpayer dollars which would have been otherwise needed to provide new on-site parking for the library. The disadvantage of utilizing the existing garage is the greatly increased travel path to the library for many patrons—including, but not limited to, the elderly and disabled. The bridge is being proposed to address this concern.

Leggett's and his staff view transportation through the lens of the driver. Sure, Montgomery is a suburban county with a lot of drivers, but it also has fantastic walkable places and some of the best transit of any suburban jurisdiction in the nation. But Leggett sees auto-oriented development as natural and walkable development as dangerous. He views the proper role of streets as carrying as many cars as possible above all, with the needs of pedestrians and transit secondary.

As with Gaithersburg West versus White Flint, Leggett cleverly ties in themes of sustainability, "Smart Growth," and more to justify suburban development patterns and oppose urban ones. His PR staff are remarkably defensive about it, too, saying I "just don't get it." It's Leggett who seems not to get it. He doesn't seem like a stupid man, but is listening too much to traditionalist transportation officials who can rattle off Level of Service letter grades but, despite some terrific examples in their county, don't recognize the value of walkable places designing around people and transit instead of driving above all.