Greater Greater Washington

Can the CCT bridge Wisconsin Ave in Bethesda?

The design of the Purple Line might mean displacing the Capital Crescent Trail from its Bethesda tunnel. Some say that an at-grade crossing of Wisconsin Avenue will be too dangerous for cyclists and pedestrians. But are there any good alternatives?

I think that many hope that if only we make a strong commitment, bring creative imagination and bring professional expertise to the problem, then we can find an attractive alternate way. Maybe something that looks like this:


Rock Creek Trail bridge over Viers Mill Road.
Image from the National Transportation Enhancements Clearinghouse.

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.


One driveway on the north side of Bethesda Ave. Image from Google Street View.

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 widethere 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 pathand 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."
My opinion about the best way forward differs from WABA's.

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.

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Comments

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It's not over until it's under.

by MDE on Dec 15, 2011 12:22 pm • linkreport

BTW, who is the author of this post? There's no byline.

by MDE on Dec 15, 2011 12:23 pm • linkreport

This may sound like a radical idea, but if the users of the trail are so adamant about keeping it in the tunnel, why not form a non-profit foundation and raise the needed funds? Nothing says committment like personal sacrifice.

And as a trail user, I would contribute.

by Dave J on Dec 15, 2011 12:32 pm • linkreport

The lack of a byline stood out to me as well when I read the first "I," MDE.

by selxic on Dec 15, 2011 12:37 pm • linkreport

Oops, this is by Wayne Phyillaier. I've fixed the byline.

by David Alpert on Dec 15, 2011 12:39 pm • linkreport

Could the bridge be in the center of the street instead of at either side? It's more visually intrusive, but if done attractively, could be nice; it also could provide some traffic calming, like a median, and wouldn't block entrances.

by David Alpert on Dec 15, 2011 12:41 pm • linkreport

Ha, that bridge over Veirs Mill was the bane of my existence for those couple years of its construction... this was for a multitude of reasons; specifically, curved bridges may be pretty, but they're a nightmare to build!

by Bossi on Dec 15, 2011 12:54 pm • linkreport

How about a commitment from the County that if they don't do the tunnel, they spend the $40M on other bike infrastructure improvements in the County, inside the beltway.

by Falls Church on Dec 15, 2011 1:05 pm • linkreport

Oh please. The problem is that the $40 million isn't there, not that no one wants to spend it.

by Dave J on Dec 15, 2011 1:13 pm • linkreport

Scrap the bridge idea, scrap the tunnel idea. The grade separation isn't worth it. Cycle track the gap.

by Alex B. on Dec 15, 2011 1:14 pm • linkreport

Let's wait until we find out how much grade separation costs before we decide if it is worth that cost. Cart < horse.

by David C on Dec 15, 2011 1:17 pm • linkreport

I agree. This is a busy downtown. Traffic is not moving 50 mph. Traffic controls will be needed to allow pedestrians to cross at grade no matter what. If that results in traffic problems, then give the cars a tunnel.

by Alan on Dec 15, 2011 1:17 pm • linkreport

I think the at-grade crossing is inferior to the original tunnel plan. But we need to keep perspective in the event that better cost estimates still show an unacceptable cost associated with that choice. There are other at-grade crossings on the CCT, including the one at Woodmont and Bethesda that crosses two roads at once.

With proper design and signalization, a surface route may be an acceptable solution that is, as Wayne points out, head and shoulders above the alternatives.

by Crickey7 on Dec 15, 2011 1:47 pm • linkreport

At grade crossing is the way to go. As previous posts have illustrated, it can be done right and with little negative impact other than waiting for a traffic signal to cross Wisconsin Avenue.

by Cassidy on Dec 15, 2011 1:49 pm • linkreport

Cost and everything aside, I think I'd rather stay level and wait at a signal than have an uninterrupted ride but have to climb however high the bridge would have to be. It seems from a utilitarian standpoint you want to try and remain level. I say this without knowing what the climbs are like in the tunnel as well because I'm not super familiar with the area in person.

by Canaan on Dec 15, 2011 2:12 pm • linkreport

Somehow, cities across the US and the world have found ways to give cars and bikes each their own street space. But not so in Bethesda, where we're trying to reinvent the wheel so we can get as many cars on Wisconsin Avenue as possible. I appreciate that Wayne is willing to look at all of the possible solutions, but there really is just one that is both cost-effective AND provides the most points of access to downtown Bethesda, and that's a on-street cycle track.

As a cyclist, I'd prefer waiting at a light to going over a bridge. In fact, I'd rather wait at a light than go through the existing tunnel.

by dan reed! on Dec 15, 2011 2:31 pm • linkreport

Yeah, there are already cross walks and stop lights right there. Just cross at the bloody crosswalks.

by Doug on Dec 15, 2011 5:09 pm • linkreport

To be clear on WABA's position, we aren't at this point asking that the county BUILD any particular option, just that they STUDY the available alternatives so that we base decisions on actual data and possibilities rather than conjecture.

If we're going to study the extent of the impacts of physical changes on the rail, let's also study the impacts of physical changes to the trail before we forego major components. I have the utmost respect for Wayne and his positions on the trail, and I may come to agree with his conclusion. (I generally do.)

But I would like the opportunity to come to a position based on a full vetting by qualified professionals of the available options. Before a decision is made, we should clearly understand the alternatives. Officials should know the impacts of the removal of grade separation and the cost of the next-best grade separated option before a vote that might remove it. And they should know what an "enhanced" on-street trail means before a vote that might adopt it.

Whatever decision is made, it's a decision that's going to have ramifications for decades. It should be made with the best available information.

by Shane (WABA) on Dec 15, 2011 5:31 pm • linkreport

[This sentence removed for violating the comment policy.]

Yeah, there are already cross walks and stop lights right there. Just cross at the bloody crosswalks.

Just using the existing streets is not a valuable option for trail users considering the hostile environment bicyclists encounter every day on the street. Kids and novices and pretty much everyone use the trail because it is a protected space to ride, walk, or run in. If the Purple Line planners want the trail to have an on-street alignment we should demand that it be a protected, buffered space and not just a bike lane or sharrows. Trail users should get their own signal at Wisconsin and should have more protected space until joining back with the existing trail. In short, it should be an on-street trail, not just "hey trail users there's the street and the rest of the trail is somewhere in that direction, good luck!"

by MLD on Dec 15, 2011 5:34 pm • linkreport

To cross the Wisconsino Ave. going west without any modifications, you will have to ride on narrow footpaths through a local park, ride along 47th to Elm, wait at a light to turn ONTO Wisconsin for one block, then turn onto Bethesda Ave. It will add two blocks to the distance travelled and is, frankly, unsafe. What cyclists will do instead, not that I condone it, is ride the wrong way on a one-way street. At the Wisconsin Ave. crossing, the majority of Bethesda Ave. car traffic crosses the crosswalk since that street ends there. That's a prescription for danger.

by Crickey7 on Dec 15, 2011 5:52 pm • linkreport

@MLD That's right I just read a 5 page article on a freaking street crossing but I must have no interest in learning about this issue. What are your amazing qualifications that make you so much less of an uninformed know nothing than me anyway?

Also, I think most kids and novices that would be out on a bike trail by themselves would also be qualified to cross a street at a cross walk. You understand how a cross walk works right? You wait for the little walking man to appear and then the cars actually stop and wait for you to cross. It's not exactly rocket science and/or fraught with danger.

by Doug on Dec 15, 2011 6:22 pm • linkreport

@MLD Another thing most casual bike riders and kids are not out there just to ride for miles and miles and get nowhere. They might like to actually like to stop at places around that intersection like the Subway or Starbucks. That's kind of inconvenient when you are trapped on some mile long bridge 50 feet above the street-scape.

by Doug on Dec 15, 2011 6:30 pm • linkreport

For those just joining this discussion, you should be aware that no one with any authority is proposing trail users just be put onto the streets to use them as they exist now. There is already an off-road alternative trail route planned for construction that would provide a separated trail at least 8' wide along the streets. It is under discussion how much this should be "enhanced" if the CCT is removed from the Air-Rights tunnel and this planned alternative route becomes the main CCT route instead of being just an optional local route. Among the enhancements proposed are to upgrade the plans to be a 12' wide trail separated from traffic, to re-align the crosswalk at Wisonsin Ave. to line up better with the corner of Willow Street, and to put stronger restrictions on traffic turning across the crosswalk.

There are no plans that I am aware of to significantly improve either the Bethesda Avenue or the Woodmont Avenue crosswalks. I remain perplexed that so much focus is being put on crossing Wisconsin Avenue, while these two CCT street crossings only one block away go apparently unnoticed.

by Wayne Phyillaier on Dec 15, 2011 7:00 pm • linkreport

I can't see any sense in building a bridge. I doubt whether recreational cyclists or even day-to-day cyclists will want to climb even more of a hill than they will already be forced to do. It's more intimidating and tiring than a well-designed crosswalk to have to go up a big hill in a chain-link tube.

Losing the tunnel is unfortunate but ease of use is more important than grade-separation. Besides, why not move the grade of the vehicles that require less human energy?

by Neil Flanagan on Dec 15, 2011 8:29 pm • linkreport

Per usual, much whining on the issue, but nothing practical. No mention of how to pay for an alternative or how to deal with inevitable disruption of all forms of transportation, if a bridge is built. The kind of bridge that would work best for bikes and walkers--long, and curvy with a gradual grade---would be utterly impractical given the desnity of buildings in the area and the limited pedestrian space.

by Rich on Dec 15, 2011 9:28 pm • linkreport

Rich, I don't really see anyone whining here, but way to start our classy.

No mention of how to pay for an alternative

That's because none is needed. Obviously it would be paid for with tax dollars. I guess it was so obvious no one thought it necessary to mention.

And the rest of your comment is either hyperbole or a restatement of the post, which you clearly didn't read.

by David C on Dec 15, 2011 9:56 pm • linkreport

Y'know, I rode around Bethesda for years, and never went through the CCT tunnel. I haven't biked in a few years but I always came off the CCT downtown and went up Old G'town. Then I could cross over to Wisconsin at Grosvenor, or if I was feeling it, at Tuckerman. From there you bounce over to Beach Drive, which takes you down into Rock Creek. Takes you up farther, to be sure, but the ride on Beach Drive is great.

I guess that's for more serious rides, though. It's hard to justify an additional $40 million to widen the tunnel, except that it's a great idea for every other reason. I can see a time, where the ride is continuous through Silver Spring -- and then either a long climb up to Columbia, or a glide down into DC. It will cost more than $40 million to do that, so the tunnel widening would just be a down payment. It would be well spent, though, if there a determined effort to make the whole region connected.

by Fischy (Ed F.) on Dec 15, 2011 11:00 pm • linkreport

Bethesda cracks me up. Users already have a pedestrian crossing at Bethesda Avenue, so what's one more? And Wisconsin avenue being a 50 mph road that imperils peoples safety? Have you seen some roads in East Moco that don't even have sidewalks? If it where truly about making the whole region connected, giving some wealthy people a bridge or tunnel (that no one would use)to avoid having them wait at a light would be way down the proprity list. This issue is the reddest of herrings when what some of these "advocates" really want is to keep East County & P.G. residents from having easy and convenient public access to the jobs in Bethesda, ie: Kill The Purple Line!

Smart growth is fine, just not in my back yard.

by Thayer-D on Dec 16, 2011 6:35 am • linkreport

One other factor that no one has mentioned that I'll just throw out here. It's likely that the retail merchants along the path would oppose any proposed bridge/tunnel/whatever-- the cyclists are potential customers and the shopkeepers would like to offer them an opportunity to pause and spend some money. Consequently, it's very unlikely that the County will spend significant funds on a project that will piss off the Bethesda business community

It's more than a little ironic that with all the talk here about the need for street life, urbanity, and non-suburbanness that everyone here simply assumes that bypassing all the Bethesda streetlife (such as it is) is what you want to do. You guys need to get with the program.

by MattF on Dec 16, 2011 7:47 am • linkreport

I believe that the solution here is a traffic light.

by tom veil on Dec 16, 2011 10:22 am • linkreport

@MattF
It's likely that the retail merchants along the path would oppose any proposed bridge/tunnel/whatever-- the cyclists are potential customers and the shopkeepers would like to offer them an opportunity to pause and spend some money.

Then why are they not exercised about the existing tunnel? Doesn't that already have the same effect?

by Steve O on Dec 17, 2011 1:22 am • linkreport

@Steve O

I'd have thought that the existing situation demonstrates my point-- one generally finds groups of cyclists hanging around the Barnes & Noble fountain area and in the line into Bethesda Bagels. However, my recollection is that the meeting of cyclists and retail in that area is mainly happenstance-- I think the tunnel predates the Bethesda Row development.

In any event, IMO, the way forward is to build on this (to me) good thing and not build a big expensive bridge/tunnel that isolates cyclists from everyone else.

by MattF on Dec 17, 2011 8:01 am • linkreport

No tunnels!

At-grade crossing with signal lights.

by Jack Love on Dec 19, 2011 4:14 pm • linkreport

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