Bridges and tunnels

December 9th, 2011

Cross posted at Greater Greater Washington with edits.

The one thing I remembered from my high school Latin class is this phrase that I thought was from Caesar in one of his letters during his Gallic War Campaign:
“One of the tragedies of life is the murder of a beautiful theory by a brutal gang of facts.”
But now I learn that even that is wrong. It is most commonly attributed to either Benjamin Franklin, or to La Rochefoucauld, François duc de, 1613-1680.

That phrase comes to mind when I consider finding an alternate to the tunnel under the Air-Rights Building for a grade-separated crossing of Wisconsin Avenue for the Capital Crescent Trail. The “beautiful theory” part is the belief held by some 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 at Viers Mill Rd.

The Rock Creek Trail Bridge over Viers Mill Road
Source: National Transportation Enhancements Clearinghouse /

But the “brutal gang of facts” part is the array of constraints presented by the urban and crowded design space in Bethesda at Wisconsin Avenue.

Don’t block the driveway unless you are willing to buy the building.

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 and parking structure driveway entrances.

map of bridge over Wisconsin Ave.

Conceptual location of bridge and bridge ramps
over Wisconsin Avenue at Bethesda Avenue
(click on image for a larger image)

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 (16′ plus 2′ assumed). 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 major driveways on either side of Bethesda Avenue.

View Larger Map

This driveway on Bethesda Ave. must not be blocked by a trail ramp.

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 Ave. bridge crossing where long ramps would not create unacceptible blockages of driveways and business entrances, we will get the same result. Crossing at Elm Street, Miller Avenue or Leland Street will also 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 south of the rest plaza 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 the rest stop and 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 Plaze, 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. See Dan Reed’s alternative view of the CCT in Bethesda at On-street crescent trail may be better for bikes and peds.

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.

map of tunnel under Wisconsin Ave.

Conceptual location of tunnel and tunnel down ramps
at Bethesda Avenue and Willow Street.
(click on image for a larger image)

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: 1) the existing elevation change along Bethesda Avenue helps for a down ramp, instead of forcing us to “chase the grade” for an up ramp, and 2) 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 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 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 cost, 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 at CCT Update.

“…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 in part. I think there is little value in exploring an alternative grade-separated option much further. The “brutal gang of facts” 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 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.

Air Rights Building off the table

December 2nd, 2011

The CCCT and other stakeholders met with Councilmember Berliner on Dec. 1 to advocate for keeping the Trail in the Bethesda tunnel, reported at the CCT News and Events. The Planning Board sent its recommendations to the Council in a Nov. 30 letter. There have been some changes since the issues were reported in earlier blog posts here.

The Council T&E Committee is now expected to take the issue up in a January 30, 2012 meeting and not on Dec. 5. This is to give MTA enough time to evaluate the options and give the Council a report.

Tearing down the Air Rights Building is apparently no longer being considered. Discussions between Council and the Planning Board have “clarified” this to mean that they will evaluate building the Purple Line station under the parking structure at the east side of the Air Rights Building, where the tunnel is a little wider. This is clearly a change from the discussion at the Planning Board on Nov. 17, when the Commisioners were talking about tearing down the building itself.

The Bethesda tunnel at the east end

CCCT succeeded in getting Councilmember Berliner to request that a more substantive response to their single-track proposal be prepared by MTA. The Councilmember noted that MTA resistance to single-track is very strong and MTA will not likely yield on this issue, but a response that quantifies the impacts of single-track impacts on the transit operations is needed to put the issue to rest.

The Planning Board is recommending in its letter that $40M is an unacceptible price to pay to keep the Trail in the tunnel. The Town of Chevy Chase is already expressing concern that the options that would place the station platforms at the east end of the tunnel or at Pearl Street might be unacceptible to the Town because of the impacts of having platform operations adjacent to residences. I believe the MTA will report substantial reductions in predicted ridership and cost effectiveness of the Purple Line system if long walking distances are created for transit riders by moving the station platform east. I believe it is most likely a surface route for the Trail is the option that will survive the selection process at the County Council next month.

The Planning Board Nov. 30 letter recommends setting up a panel of agencies and the Town of Chevy Chase to evaluate design options for the Trail surface route, and lists design treatments that can be considered to make the route safer and more attractive. CCCT asked Councilmember Berliner to put the CCCT, WABA and other trail stakeholder groups on the panel. WABA and CCCT also advocated at the meeting with Councilmember Berliner that planners should give a trail bridge or tunnel serious consideration to avoid the at-grade Trail crossing at the Bethesda Avenue/Wisconsin Avenue intersection if the Trail is removed from the Bethesda tunnel.

The engineer in me is very doubtful that a successful trail bridge or tunnel across Wisconsin Avenue can fit into this area. The constraints imposed by the streets, existing major buildings, and elevation change from Woodmont Avenue to Wisconsin Avenue will force designs that are very unattractive to trail users, even if cost is no issue. But I’d be happy to be proven wrong on this – just show us the design concept that works. In the mean time, we should not buy into “Save the Trail” and other Purple Line opponents’ efforts to hype the danger of crossing Wisconsin Avenue to hysterical levels. Yes, any at-grade crossing of a busy highway should be avoided wherever an attractive trail bridge or underpass is possible for a regional trail like the CCT. But no, the trail network will not be destroyed if we must cross in a protected crosswalk at a well redesigned intersection.

Bikesharing is coming – but where is the infrastructure?

November 30th, 2011

I was unable to attend the Nov. 29 Bike Share planning workshop hosted by MC DOT, but the WABA blog post Bikesharing Growing to Montgomery County gives a good account.

A major concern I had about whether Bike Share can work in Silver Spring was whether bikeshare stations clustered around Silver Spring might be too isolated from the system in D.C. The WABA post reports that planners are addressing this:

…A side note, in planning talks DDOT has agreed to expand bikeshare stations north between the system core and the new clusters in Bethesda, Silver Spring & Takoma Park to help connect the entire system.

The public is invited to submit ideas for locations of future bikeshare stations at the Capital Bikeshare crowdsourcing map.

One important item is still missing from the plan – a serious commitment to beef up the bicycling infrastructure to make the street network more bike friendly. Much can be done with signs and paint. Bike lanes, bike sharrows, and signs marking routes and reminding all to share the road can make a difference. Yet little has been done to mark streets in the Silver Spring CBD that have long been identified in the Master Plans as on-road bike routes. Two examples:
1) Spring Street was recently restriped to narrow the traffic lanes by creating approx. 6′ wide “dead zones” adjacent to the center median in a several block long section centered at Second Avenue. MCDOT could as easily have narrowed the traffic lanes by placing them adjacent to the center median, and placing full width bike lanes on the outside.
2) When Cameron Street was restriped there was room for bike lanes, yet MCDOT instead chose to install a center turn lane that was not needed.

I am excited that MCDOT appears to be serious about bringing bikesharing to Montgomery County. Now if we can only get MCDOT to read the approved Master Plans when it restripes streets, and use stripes and sharrows to show that bikes have their place on the road.

Fenwick Station moving forward

November 23rd, 2011

The future Fenwick Station at Spring Street and Second Avenue
Space is being set aside for a bike share station.
(Click on image for a larger scale image.)

Representatives for the future Fenwick Station briefed community members on the project at a November 22 meeting. The building will have 350+/- residential units and no retail. The plans call for a section of the Green Trail to be built in front of the building along Second Avenue, and an access trail to the future CCT to be built along Spring Street, see Green Trail at Fenwick Station. They will reserve space for a future bike share station at a small public plaza at the Spring Street/Second Avenue corner.

They plan to submit their site plan for approval in December and hope for Planning Board approval in April. Their contract with the Post Office requires them to give 150 days notice before the Post Office has to leave.

Taking a hard look at the tunnel

November 19th, 2011

A $40M price tag on keeping the trail in the Bethesda Tunnel should prompt us to take a hard look at what the $40M would buy. I’m taking a second look, and the trail that we would have in the tunnel over the Purple Line looks too much like damaged goods to pay such a premium price to save.

Last year I wrote about Bethesda tunnel west. Cyclists need to reconsider the narrow switchback ramp at the west end of the tunnel that will require dismounting. Is this what we want? Is it worth fighting hard for?

MTA concept for the CCT in the Bethesda tunnel
(click on the image for a large image)
Source: MTA Plan and Profile – Trail, September 2010

Dan Reed wrote a thought provoking post for Greater Greater Washington, On-street Crescent Trail may be better for bikes and peds. Among the comments to the post is my response to a comment from Jack Cochrane of CycleMoco:


I like the tunnel, and this may sound like sour grapes now that it is becoming ever more apparent keeping the trail in the tunnel is not practical, but -

The plan for rebuilding the trail to be overhead the Purple Line in the tunnel will not give us the direct connection you would like. If going east from Woodmont Avenue, cyclists would have to pass through the conflicts in a very pedestrian active Woodmont Plaza to get to the tunnel entrance. Then they would be required to dismount, and walk up a tortuous switchback ramp built into the back side of a new JBG building to get to the overhead. The trail in the overhead will be at least as wide as the trail is in the tunnel today, but will have a vertical clearance as little as 8′. This will make it feel much more confining than it does today.

The proposed surface route will be less than 400′ longer than the tunnel route. You will only need to stop riding if you have to wait for the light at Wisconsin Avenue. A 10-12′ wide shared use trail on the north side of Bethesda Avenue and a shared use trail or cycletracks on Willow can separate cyclists from traffic.

Quite frankly, if I were to cycle through Bethesda and have that choice, I’ll take the surface route rather than deal with the dismount and walk up the narrow switchback ramp into the tunnel at the west end. Pedestrians and families with small children on bikes might still prefer the tunnel route, but few adult cyclists will use it under those conditions. You know better than most how adverse cyclists are to dismount zones. The tunnel route is not worth $40M for cyclists.

Maybe I am suffering from a sour grapes syndrome now, but the tunnel route does not look so hot when we take our rose colored glasses off and look straight at that switchback ramp.

Planning Board to JBG – “Think again.”

November 18th, 2011

The Planning Board took up the Bethesda Tunnel issue at its Nov. 17 meeting and decided that all options should be considered to keep the trail in the tunnel. As reported in the Washington Post and WashCycle, the Planning Board asked that placing the Purple Line Bethesda Station on the east side of Wisconsin Avenue or taking down a building over the tunnel be evaluated.

The Planning Board heard the Coalition for the Capital Crescent Trail argue that single-track in the tunnel should also be considered, see the CCCT single-track position. MTA argued that single-track in the tunnel would make the Purple Line slow and too unreliable. the Planning Board accepted the MTA opinion and did not recommend the single-track for further evaluation. In my view, that was a mistake.

Source: CCCT single-track position

It may turn out that the MTA opinion that single-track will interfere with Purple Line operations too much is true. But MTA failed to present anything to substantiate that opinion at the hearing. MTA Project Manager Mike Madden attempted to point to an earlier single-track study as proof that single-track in the tunnel would not support the needed headways. That study was for a much longer section along the line between tunnels, stations, and one of Madden’s own engineers consulting engineer Harriet Levine admitted that study was not relevant for this case. MTA argued that they would have to make the north platform much larger if the south platform was removed, but did not explain why this is so. Under the current plan, all passengers getting off a train on the north track would exit to the north platform to go to the elevators and stairs on that side. No one would have any reason to exit a train to the south side, so the north side platform must be wide enough to handle all traffic regardless of whether a south side platform is present. And, in any case, there is room to expand the north side platform while still preserving a trail if the south side platform and track are removed. The MTA said they could not give up the ability to keep another train at Bethesda on the south track, but they did not explain why the tail track presented in the CCCT statement would not serve to do this. In short, the MTA staff were pulling ideas off the top of their heads.

If the Planning Board can ask the MTA to evaluate tearing down large buildings or moving the transit station hundreds of feet away from the connection to Metro, then the Planning Board can also ask MTA to substantiate their assertions that single-track will not work. If single-track can work, it would be by far the easiest and cheapest to build.

The Planning Board did send a very clear message that it will make the alternate trail surface route a priority, especially if the trail is removed from the tunnel. Representatives from JBG Associates gave testimony that a shared use trail along the north side of Bethesda Avenue would conflict with their plans, and therefore the trail should be bike lanes on Bethesda Avenue instead. JBG had earlier planned to build an office and retail building at the northeast corner of Woodmont and Bethesda Avenues, see the CCCT news report. But JBG now intends to come to the Planning Board soon with a request to instead build a large hotel there, with a hotel driveway entrance. The JBG representatives felt that a busy shared use trail would not be consistent with their proposed driveway.

Planning Board Chair Francoise Carrier agreed that a busy trail on the north side of Bethesda Avenue and a hotel driveway entrance would conflict, but she pointed out the trail has been in the Master Plans since the 1994 Bethesda Sector Plan.

Capital Crescent Trail Street Level Route
Source, 1994 Bethesda Sector Plan

The Planning Board Chair told the JBG representatives they should reconsider their plans and not bring a plan to the Board that is not compatible with the Master Plan. The signal was clear – if a hotel and the trail cannot both work here, a hotel will not be approved. If the Planning Board and County Council can show this priority consistently along the surface route, then it can become even better than the trail Dan Reed envisions at On street CCT may be better for bikes and peds

Learning to like the Bethesda surface route

November 10th, 2011

The Montgomery County Planning Board is considering whether to recommend to the County Council that we go forward with keeping the CCT in the Bethesda Tunnel, now that the cost estimate has risen to approx. $40M, or to recommend using an alternative route along Bethesda streets instead. On November 3 the Board and staff took a tour of the tunnel to look at the options. On November 17 the Planning Board will have a worksession on this and other issues including lighting, landscaping, and connecting to the Rock Creek Trail. The Planning Board will hear staff recommendations and take public input. Information on how to give testimony is on the M-NCPPC website agenda page. Also now available on the website is the M-NCCPC staff report with the recommendations that will be presented to the Planning Board on November 17.

The staff recommendations come with a very good analysis of the cost and benefits of the tunnel route, and also a thorough analysis of the alternative surface routes. Regarding the tunnel route, the staff recommends:

It appears that more design work is needed before a recommendation can be made with confidence on whether to construct the Capital Crescent Trail in the tunnel.
a. Should further engineering investigation reveal a much lower cost or risk differential or should a mechanism present itself to provide the funds to reduce the public outlay and/or risk to the Apex Building, constructing the trail may yet be found to be feasible.
b. We recommend that MTA brief the County Council in six months time with updated cost estimates and risk comparisons so that this decision can be made with greater assurance.
c. If the cost differential remains, the County Council should determine the tunnel route to be financially infeasible and concentrate more effort on building the planned surface trail to accommodate the volume and variety of user groups.

There may be something uncovered in the tunnel structures during a six-month engineering investigation that will overturn the huge cost differential we are looking at now. But I doubt it. The CCCT is suggesting a short single-track Purple Line section could be used at the tunnel, to make it easy to keep the trail in the tunnel. But if that single-track concept is found to be not practical, then we are likely looking at a decision to reroute the CCT on Bethesda streets.

The M-NCPPC staff report gives a good description of three alternative routes, and recommends the route along Bethesda Avenue (the dashed yellow route below).

Alternate CCT surface routes in Bethesda
Source: M-NCCPC staff report

The Bethesda Avenue Route has long been proposed as an alternative route to be built in addition to the trail in the tunnel, for local trail access. The M-NCCPC staff recommend that, in the event this becomes THE route of the CCT, this route be developed much more extensively than has been planned. Their report lists specific recommendations for shared use off-road trail sections down Bethesda Avenue, Willow Street and 47th Street and to realign the Wisconsin Avenue crosswalk. But most impressive are the recommendations to change the traffic lights:

Intersection of Wisconsin Ave and Bethesda Ave: Crossing Wisconsin Ave is the greatest impediment to creating a viable surface alignment. Therefore, it is critical to prioritize pedestrians crossing Wisconsin Ave. We recommend eliminating the conflicts for pedestrians crossing Wisconsin Ave by either:
  • Prohibiting left turns from Bethesda Ave to northbound Wisconsin Ave and prohibiting right turns on red in the southbound direction to eliminate all conflicts between trail users and motor vehicles
  • Providing a pedestrian only phase.

Both of these modifications would likely require signal retiming along Wisconsin Ave.

If all of these changes were in place, then I would find this route to be almost as good as the route through the tunnel. This surface route is about 400′ longer than the tunnel route and has a wait for a signal at Wisconsin Avenue. But it would be in the open and partially in a local park rather than being in a long tunnel. IF the signals at Wisconsin Avenue can be changed to eliminate the interferences with motor vehicle turning traffic, then crossing Wisconsin Avenue would be safer than is crossing Bethesda Avenue and Woodmont Avenue at the CCT Bethesda Trailhead today.

The tunnel route remains the most direct and safest CCT route. We may find a way to save it if the cost differential changes on further study, or if we find that single-track can work at the Bethesda Purple Line station. But losing the tunnel route is not an existential threat to the future CCT. I can learn to like the alternative Bethesda Avenue route if it is done right.

Planning Board tours tunnel

November 4th, 2011

The Montgomery County Planning Board toured the Bethesda Tunnel and the Interim CCT connection to the Rock Creek Trail yesterday to examine CCT cost issues. MTA and Montgomery County DOT and M-NCPPC staff briefed them on costs of rebuilding the CCT with the Purple Line.

Route of the Nov. 3 Planning Board tour at Bethesda
Source: Tour agenda and MTA CCT cost report (a pdf file)

Several dozen neighborhood residents also turned out for the tour, many carrying “Save the Trail” placards. Katherine Shaver was there to report for the Washington Post. Planning Board Chair Francoise Carrier reminded those present that the purpose of the tour was for the Planning Board to ask questions of the Purple Line planners. She invited the public to present comments at the Nov. 17 Planning Board work session.

Planning Board Chair Francoise Carrier addresses the public.

I’ve already posted that is important we not get tunnel vision and put too much focus on the Bethesda Tunnel while losing sight of the bigger picture for the whole trail. But I was on the Bethesda part of the tour, and would like to offer comments on several issues at the Bethesda Tunnel of interest to trail users. I’m not advocating hard for any one idea yet – I’m still trying to get a clearer picture on what the realistic choices are to make both the Purple Line and the CCT work well here:

1) Cost to put CCT over the Purple Line through the tunnel.

MTA Purple Line project manager Mike Madden stated that much of the cost and risk to dig to lower the Purple Line below the current grade, necessary to fit a trail overhead, is associated with stabilizing 35 beams that support the Apex Building. He also said that even if the Purple Line is built at the current grade without the CCT, there still will be some beams near the west end of the tunnel that will require stabilizing. MTA does not know yet how many beams would still require stabilizing even if they do not dig.

The cost of building the trail over the Purple Line in the tunnel is estimated to be 43% of the total estimated $103M trail cost. (Source: Tour agenda and MTA CCT cost report.) But that cost includes the cost of stabilizing all of the 35 beams. We need to subtract the cost of stabilizing the beams that must be done even if we do not dig, from the cost of stabilizing all 35 beams if we do dig, to know the stabilization cost that is due to the CCT.

Adjusting the cost to reflect the cost difference for stabilizing the beams will bring the CCT cost estimate down a little. And the fact that MTA does not yet know how many beams must be stabilized if we do not dig suggests they have not done enough exploration yet to have a firm cost estimate. We should have better information before we make decisions based on cost.

2) Fitting a pedestrain trail alongside the Purple Line.

WashCycle raised the question in recent blog post comments whether it might be possible to have a narrow trail alongside the Purple Line in the tunnel, without digging. The tunnel under the Apex building west of Wisconsin Ave. is wide enough to permit this – plans already call for pedestrian access from the west tunnel portal to the Purple Line platform and Metro elevators near the middle of the tunnel. But the tunnel under the Air Rights building at the east end is narrower, only 32′ wide from wall to wall. Recent Purple Line profile drawings show two light-rail tracks have a typical 29′ wide profile. But these profiles are for unconstrained spaces where the Purple Line runs at speed. It may be acceptible to reduce the separation distances between tracks and between the tracks and the side structures (i.e. poles to support the catenary wires) in the tunnel where vehicle speeds will be very low – perhaps to achieve a profile as little as 24′ wide which would leave room for an 8′ wide path in a 32′ wide total space. But you would need to be able to use all of the tunnel width from wall to wall, with no setbacks from below-grade foundation structures.

I raised this issue with MTA engineers at the Nov. 2 Open House at the National 4-H Education Center in Chevy Chase. They had not considered this yet, but agreed it should be looked at seriously. They had two concerns that might wreck the idea: 1) The tunnel width under the Wisconsin Avenue bridge might be less than it is under the Air Rights Building, and 2) The tunnel has a curve, which will require a wider spacing between tracks to allow for the transit vehicle “overhang” on the curve.

During the Nov. 3 tour we saw the tunnel under the Wisconsin Avenue bridge. Slopes down from the bridge abutment structures on both sides of the tunnel do indeed pinch the tunnel to be narrower than under the Air Rights Building. But Mike Madden explained that these were only dirt slopes, covered with concrete for erosion control. The abutment structures that support the bridge are set well back. The slopes can be cut back, and retaining walls can be used for the erosion control without disturbing any bridge structures. This could make the tunnel wider under the Wisconsin Avenue Bridge than under the Air Rights Building.

It was apparent during the walk through that the curvature of the tunnel under the Air Rights Building was only at the west side of the building and very slight. It appears likely that any allowance required for vehicle “overhang” at the curve would be slight. Mike Madden also stated that the walls of the Air Rights Building tunnel were structurally stable and extended deep enough so that they would not need to be modified, even if digging was needed.

Profile of Purple Line with CCT under the Air Rights Building
Source: Tour agenda and MTA CCT cost report (a pdf file)

It therefore appears to be very feasible to have a 6-8′ wide walking trail east through the tunnel from the Purple Line platform and Metro elevators to the east end tunnel portal, if the decision is made to not carry the CCT through the tunnel over the top of the Purple Line. The profile above shows the Purple Line with the CCT overhead. But if the CCT supporting structures are absent, the light-rail tracks can be shifted to be closer together and close to the south wall. A 6-8′ wide walking path could be on the north side. The walking path would only need to be several feet higher and separated from transit by a low fence in order to feel safe near transit, given the low speeds of the transit vehicles approaching the station platform.

Purple Line supporters should join trail users to advocate for this path, in the event the CCT is removed from the tunnel. This passageway would provide important pedestrian access between the Purple Line platform and the neighborhoods, businesses and schools east of Wisconsin Avenue. The Purple Line should carry the cost of building it since the Purple Line needs this access path.

3) Single-track Purple Line in the tunnel.

CCCT Chair Ron Tripp put the idea before the CCCT Board at the October board meeting that we should propose that the Purple Line be single-track in the Bethesda Tunnel. This would allow a full width CCT to share the tunnel with the Purple Line without any digging. I’m not a fan of this idea, but it does have enough merit to be taken seriously. The CCCT has not settled on its recommedations to address the Bethesda Tunnel cost issues yet, but single-track may be on the list.

Councilmember Berliner proposed a much longer single-track section for the Purple Line several years ago. His proposal was to single-track a 3500′ long section from the Bethesda Tunnel to the west side of the Columbia Country Club. The principal goal was to minimize the impacts on the trees and adjacent homeowners where the r.o.w. is only 66′ wide and where room to buffer the neighborhood is more limited than elsewhere on the r.o.w.

MTA studied Berliner’s single-track proposal and issued a MTA single track study (a pdf) with strong recommendations against the idea. MTA found that being able to operate only one vehicle between the Country Club and the Bethesda Station at a time would unacceptibly constrain the headway, to be at least 7 minutes. The minimum necessary headway needed to carry the heavy use in this section is believed to be 6 minutes or less. MTA was also concerned that since transit vehicles would have to leave the Bethesda station immediately, schedule problems that develop could not be corrected and would ripple through the whole system. MTA was also concerned that having only one track at Bethesda would prevent them from holding a back-up vehicle there to fill gaps in service. And finally MTA found that few trees would actually be saved during construction. Based on these findings, the County Council reluctantly dropped the idea.

The proposal to go to single-track only in the Bethesda Tunnel would result in an approx. 1500′ length of single-track, vs. the 3500′ length of Councilmember Berliner’s earlier proposal. I roughly guess that this shorter distance would take at least 1 minute off the time it would take a train to traverse the single-track section in each direction. That would mean a headway of less than 5 minutes might be possible – meeting the requirement for a 6 minute headway or shorter. That’s good. But I suspect the same issues about trains being required to leave the Bethesda Station immediately and not being able to store a back-up vehicle there would remain.

Single-track at a station, especially an end-of-line station, is a departure from what we usually see where single-track has been attempted. The parent of the Purple Line concept, the single-track Georgetown Branch Trolley, was actually planned to be double-track at all five stations along the line between Silver Spring and Bethesda, including at the Bethesda Station in the tunnel. The plan was to have trains pass at the station platforms. The stations were planned to be roughly equally spaced, at distances that would enable trains to pass at the stations and still maintain 6 minute headways. A key to making it all work was that the Georgetown Branch Trolley was to be a “closed” system that would never run on-street, so it would be possible to keep trains precisely spaced at about equal intervals. Keeping to carefully spaced intervals at all times is not considered to be feasible for the Purple Line because the Purple Line is an open system, that will run in streets and have traffic lights in parts of its route east of Silver Spring. These potential traffic interferences can introduce too much variation in train intervals for them to pass only at the stations without forcing trains to wait. Variation in train intervals is best corrected at the end-of-line stations, but the needed corrections may not be possible at a single-track end-of-line station.

Single tracking only at the Bethesda Station may be judged to create unacceptible problems for efficient transit operations. But this proposal to single-track a very short section has enough difference from Councilmember Berliner’s earlier proposal for a much longer section to merit a serious look from people who understand transit operations much better than I.

4) Safety of the Trail.

This is not a design idea, but an observation about irrational, and potentially damaging, assertions being made by some about safety of the trail in the tunnel.

Comments were heard during the Planning Board tour from the “Save the Trail” people that if the trail is elevated and placed in a confined space over the Purple Line, with no way to get off except at the ends, and without being able to see to the other end of the tunnel before entering, then the trail would be too dangerous and no one would want to use it. Ajay Bhatt, President of Friends of the Capital Crescent Trail, is quoted by Katherine Shaver in the Washington Post as saying:

“I can’t imagine people would enjoy that trail experience,” Bhatt said of an enclosed trail above trains, and “it seems like it will be a safety hazard” by attracting crime.

The problem with taking this position is that the existing trail looks like this now:

The trail we have in the tunnel now.

The existing trail is in a confined space, with no way to get off except at the ends, and without being able to see to the end of the tunnel before entering. So exactly how does Ajay Bhatt think that just elevating the trail by about 10′ will suddenly transform a trail he claims to badly want to save into a trail that is such a safety hazard that he cannot imagine anyone wanting to use it?

The danger in this “Save the Trail” position is that we are asking the Planning Board and County Council to spend many millions of dollars to keep the trail in the tunnel. If we raise groundless fears that a trail in the tunnel cannot be made safe and attractive, in a misplaced effort to make the Purple Line look bad, we seriously undercut our request to public officials to spend scarce money to keep the trail in the tunnel.

The second half of the Planning Board tour at Bethesda was along the proposed alternate street route for the CCT. Several ideas came up for discussion about how to put this route on steroids if the CCT is removed from the tunnel. But I’ve already written too much for one post, the alternate route will be the subject of a future post.

Tunnel vision

November 1st, 2011

Cross posted with edits at Greater Greater Washington

I’m sorry to be late to join the discussion about the bad news CCT costs along future Purple Line rise. There is a serious threat that the trail may be removed from the Bethesda Tunnel to reduce cost. WashCycle has opened the discussion with a good analysis of the major issues. The Montgomery County Planning Board is seriously considering removing the trail from the tunnel and several other cost reduction measures, and will be taking a walking tour of the trail to gather backbround information on Nov. 3. The M-NCPPC Capital Crescent Tour document (a pdf file) describes the walking tour agenda, and presents the detailed MTA CCT cost analysis report.

No testimony will be taken during the Nov. 3 Planning Board walking tour. The Planning Board will take the CCT cost issues up again at its Nov. 17 work session, and public testimony is expected to be taken then. Trail and cycling advocates need to sort through the cost issues and be ready to present thoughtful and convincing arguments by Nov. 17.

The early response from “Save the Trail” advocates has been a knee jerk reaction that the CCT will be destroyed if trail users are forced to use the alternative alignment that crosses Wisconsin Avenue at-grade.

Two alternative CCT routes at the Bethesda Tunnel
(source: Planning Board CCT tour agenda

I support doing everything within reason to keep the CCT in the Bethesda Tunnel, because every at-grade crossing of a busy highway takes some of the safety and convenience away from the trail that makes it so special. I made the case for keeping the trail in the tunnel when the estimated cost was $60M in a Dec. 2010 post. With the cost now approaching $100M, the case becomes harder to make and the tunnel route for the CCT is at risk.

Trail supporters have a difficult decisions to make about how to best go about fighting to keep the CCT in the Bethesda Tunnel. But making the Bethesda Tunnel our paramount issue and declaring ourselves to be opposed to the Purple Line to “Save the Trail” would be to have severe “tunnel vision”. The map, below, has been presented often in prior posts but is worth showing again .

The completed CCT will link two large urban centers and will connect to the Metropolitan Branch Trail to complete a major regional trail system.
(partial Capital Crescent Trail map from:

If our goal is to have a regional trail, then we must remember that there is an approx. 1.5 mile long section at Silver Spring that is incomplete, and remains on-road. There are seven at-grade crossings of streets at traffic lights on the existing Georgetown Branch Trail east of the Bethesda Tunnel, including three crossings of multi-lane state highways (Connecticut Avenue, 16th Street, and Colesville Road). The rebuilt trail alongside the Purple Line would replace all 1.5 miles of on-road route with a completely off-road trail into downtown Silver Spring. All seven at-grade crossings at lights would be replaced by grade-separated crossings. Prospects for ever completing the trail and removing these seven at-grade crossings east of Bethesda are very poor without the Purple Line.

Losing the Bethesda Tunnel would be a significant loss for the CCT. We need to fight to save it. But the CCT will be more continuous and safer when rebuilt alongside the Purple Line than it is today, even if we lose the Bethesda Tunnel. Killing the Purple Line would harm the future trail much more than it would help it.

Keeping it in balance at Lyttonsville

October 6th, 2011

The MTA returned to Lyttonsville for a neighborhood meeting on Oct. 3, to follow-up on questions raised during the Sept. 13 Lyttonsville neighborhood work group meeting. As reported in the Gazette at Silver Spring residents question Purple Line redesign, some local residents remain very unhappy about the MTA proposal to “flip” the CCT to the north side of the project and to move the maintenance facility to the east side of Lyttonsville Place. Residents expressed strong views that this proposed change was a major “supersizing” of the storage yards and maintenance facility from anything that they had been shown before, and many felt the neighborhood had been blindsided at the Sept. 13 meeting with this major change. The two major concerns of local residents about the future CCT appear to be that the proposed flip would cause the loss of shade along the trail and would make access to the trail more difficult.

I saw little at this second meeting that would change my first assessment of the new plans for the CCT at Lyttonsville. I feel that the Lyttonsville Civic Association representatives and neighbors are greatly overstating the significance of the changes the MTA is proposing. The CCT can work well in this area with the new proposed alignment, provided proper attention is given to several key design issues. In particular, the new proposal should be tweeked to keep more green buffer along the trail and to improve the local access routes.

Warning: This is a long post. If you would rather not get into the neighborhood issues, then skip down to the discussion of the CCT green buffer and local access issues.

The scope and size: Not greatly increased from before.

Numerous speakers at the meeting complained bitterly that the MTA was greatly expanding the scope of the project at Lyttonsville with little prior notice. Claims were made that this was the first time MTA had shown that the project would take all of the area between the Georgetown Branch Trail corridor and Brookville Road. It was even asserted by one speaker that the plans for double tracking and running transit vehicles on headways as short as 6 minutes in the Lyttonsville area were new. These assertions, though certainly heartfelt, simply do not line up well with the public record. MTA has posted links to the presentation material for the two meetings on its website at Lyttonsville station area work group. The MTA presentation given at this second meeting addressed the history of the project, and is available as a pdf file at Oct. 3, 2011 MTA Presentation.

One can find from the history that the transit alignment was described clearly as being double tracked at Lyttonsville, and running as frequently as 6 minute headways, as early as 1990. (See, for example, the pdf file 1990 Georgetown Branch Master Plan, p. 44, for specification of double tracking along the northern side of Lyttonsville neighborhood.) The maintenance facility has grown considerably from that shown in the 1990 plan, but it was shown nearly three years ago, in this sketch presented at the Nov. 2008 public hearing, that the maintenance facility would require taking many of the businesses on the south side of Brookville Road from Lyttonsville Place to Stewart Avenue:

Lyttonsville Station as presented at the Nov. 2008 Public Hearing
(source: Oct. 3, 2011 MTA Presentation)

The Oct. 3 MTA Presentation also showed drawings that had been presented to the community in Feb. and Oct. of 2009 where all of the businesses on Brookville Road to Stewart Ave. would be impacted except one (the Counter Intelligence showroom) at the Stewart Avenue corner. Claims being made by the neighborhood that the project suddenly grew dramatically with the plan shown at the September 13 meeting don’t hold up.

Neighborhood disturbance: Little worse than what is there now.

The changes from that earlier LPA plan and the new plan do not much change the total scale, but they do change relative positions substantially. Those changes are:
1) The location of the trail, Purple Line tracks, and storage tracks are flipped, mostly with little change to the overall project footprint, to put the trail and Purple Line tracks on the north side of the project further from the Lyttonsville neighborhood.
2) The maintenance building is moved to be east of the Lyttonsville Place Bridge and closer to the Claridge House.
3) A 200 car, two level parking garage is new to the project, to be built south of the maintenance building, and
4) Stewart Avenue will be realigned with a new bridge over the Purple Line, bringing the project closer to the homes at the end of Albert Stewart Lane.

The MTA pdf file Design Option Roll Map shows the location of these features. MTA also presented the following sketch to show relative locations at the Claridge House:

The maintenance building and parking garage near the Claridge House
(Click on the image for a larger view.)

The MTA presentation makes several important points about the impacts of these changes on the neighborhood:
1) The noisiest and most active part of the system is the main Purple Line tracks and station, and they have been moved to be substantially farther from the Lyttonsville neighborhood.
2) The maintenance building is expected to be relatively quiet since work is performed inside. The storage tracks may be noisier with activity from shuttling vehicles back and forth. Switching the maintenance building location with the storage track location can help reduce the noise near the Claridge House from the prior plan.
3) The new configuration allows through movements on the storage tracks, which should reduce the amount of shuttling needed to access the vehicles.

Many residents at the meeting appeared to be very skeptical of the MTA claims that the new configuration would not seriously degrade their neighborhood. But I think an obvious fact was largely ignored by the neighbors during the discussion – that while the Lyttonsville residential area is very attractive, the area between the north side of the residences and Brookville Road is a noisy dump, and could hardly be made worse by the Purple Line. One only needs to walk around the area and listen to realize this is true. I especially encourage those who think they already know the area to do this. People who live in an area quickly become deaf to the constant noises that are in the background, and need to consciously listen to experience it as it really is.

I offer the following two Google Map views as a poor substitute for a walking tour:

View Larger Map
Behind the Claridge House, where the two level
parking garage is planned.

On my two most recent visits to the area above, a heavy front-end loader was busy moving materials in the landscaping yard near the Claridge House swimming pool. The engine noise and backing signal noise it was generating easily exceeded anything that would come from a light-rail vehicle.

View Larger Map
Looking toward the back yards of homes on
Albert Stewart Lane from Stewart Avenue

I regularly see a forklift noisily working in the Serra Stone staging yard immediately behind the homes seen in the view above. Stewart Avenue serves dozens of businesses, and there are nearly 200 parking spaces and vehicle loading spaces associated with those businesses. This draws considerable heavy truck and delivery vehicle traffic in addition to the automobile traffic. I am not convinced that removing the Serra Stone yard for the Stewart Avenue realignment, and adding automobile traffic from 200 Purple Line employees coming to the new parking garage, will have a heavy impact on the homes in this area compared to what is there now.

Shade on the CCT: Little difference from the prior plan, a green buffer should be added to either plan.

Several neighbors commented at the Oct. 3 meeting that the new Purple Line plan left the CCT with no shade through the Lyttonsville Station area. The trail would be adjacent to Brookville Road, and the MTA plan shows no green buffer at all between the trail and either Brookville Road on one side and the Purple Line tracks on the other side.

This is a big issue, but it is not a new problem that results from the “flip” from the previous plan. Close inspection of the previous plan, shown in the pdf file LPA Roll Map, reveals that the previous plan also left the CCT without shade through this area. The future CCT is pushed south from the current location of the Interim Trail, pushing into the industrial yards and eliminating the thin line of trees there now. The CCT would be left with no buffer from the treeless industrial yards. This issue must be addressed, regardless of whether the plan is flipped or not.

Trail supporters need to press MTA and other decision makers to provide some green space alongside the CCT in this area to preserve the trail experience. The Impact Comparison map suggests how this can be done:

MTA Impact Comparison map
(Click on the image for the full map.)

The map above shows the areas as shaded in green where the proposed “flip” would reduce the impact from the previous plan. There is considerable green area on the south side of the Purple Line project adjacent to the WSSC facility, west of Lyttonsville Place. I propose that area be reclaimed for the project, to expand the total width of the project to enable the storage tracks and Purple Line tracks to be shifted south by 10-15′. This shift would create space for a 10-15′ wide planted buffer along the CCT at the north side.

Expanding the project on the east side of Lyttonsville Place to also create room for a planted buffer there will have more impact on the properties along the south side, but nonetheless this should be seriously considered. The new “flip” plan has moved the Purple Line tracks farther from the Lyttonsville neighborhood than before – we can move the tracks 10-15′ south and still have the main line tracks be farther from the neighborhood than in the prior plan. In my view having the mass of tracks and trail be softened by adding a green strip with trees beside the trail would more than compensate the view from the neighborhood for having a slightly wider total project. And the experience for both the trail user and transit user will be greatly improved with small trees and green space alongside.

This is important – we need to get more green space into the design, and we can do so if we make it a priority.

Local CCT access: Give attention to the four bridges.

Residents of Lyttonsville are understandably concerned that moving the CCT to be alongside Brookville Road will make access to the CCT more difficult for them. But there is a trade-off here, since those working at the Army Walter Reed Annex and the businesses in the industrial park will find it easier to reach the CCT. If the MTA goes forward with the new plan, the design should incorporate upgrades to all four bridges crossing over the Purple Line so that Lyttonsville residents have the best local access to the trail possible under the circumstances.

At Grubb Road: The MTA drawing for the new plan shows that access to the trail from Grubb Road/Terrace Drive to the CCT will be by a new pedestrian bridge over the Purple Line where the access trail to the Interim Trail is now. But the plan also shows a long switchback ramp on the south side of the Purple Line to gain the elevation needed for the bridge to clear the Purple Line. I believe this switchback is not needed, and that a cursory inspection of the area by MTA will confirm that little more is needed here than a short ramp.

The old Brookville Pike crossed over the B&O Railroad tracks at this location for many years. The crossing is shown in the 1918 Right-of-Way and Track Map of the Southern Metropolitan Railroad Company, and the map has an annotation that the Mont. Co. Council authorized the removal of the bridge in 1967. The western abutment to that bridge is still in place and can be seen from the Interim CCT.

The eastern abutment to the Brookville Pike Bridge,
across the Interim CCT from the Grubb Road access path.

Brookville Pike worked with the existing grade in the area to get enough elevation to clear the railroad – it used no switchback. When the Grubb Road access path to the Interim Trail was built in 1996, the western bridge abutment had to be removed so the path could be cut into the hill to get down to the railroad grade. There is no need for a switchback here for a new pedestrian bridge if we use the existing elevations in the area effectively.

At Lyttonsville Place: Under the new plan, anyone wanting to reach the CCT or Purple Line Station from the Claridge House area will need to use a rebuilt Lyttonsville Place Bridge. Traffic on the roadway is heavy and fast. It will be essential that the new bridge have a generous pedestrian and bicycling path with a physical barrier separating it from the roadway. I would suggest at least a 5′ sidewalk and adjacent 8′ bicycle path on the east side of the bridge. This pathway should extend the full length of Lyttonsville Place to Michigan Avenue.

At Stewart Avenue: As for the Lyttonsville Place Bridge, the new Stewart Avenue Bridge will be an essential crossing for area residents to reach the CCT and Purple Line Station. It will also need a strong pedestrian/bicycle path on its west side. The path should extend down Stewart Avenue to Kansas Avenue.

At Talbot Avenue: Under the new plan, local access to the CCT that had been planned at the end of Kansas Avenue and Michigan Avenue will be lost. Lyttonsville residents who want to go east on the CCT from the general area of Rosemary Hills Elementary School will want to access the CCT via. Talbot Avenue and the Talbot Avenue Bridge. This access would be important even under the old plan, because pedestrians will strongly resist walking north to a Michigan Avenue access point if they intend to go south on the CCT.

The Talbot Avenue Bridge is planned to be extended at its west end to accommodate the Purple Line, but to remain with the same center span structure in the same location. Little can be done to improve pedestrian access on the narrow bridge itself. But motor vehicle traffic patterns to the bridge are not expected to change, and the tight curves and stop signs slow motor vehicles so that the bridge works reasonably well now to carry the existing Georgetown Branch Trail traffic. We can live with the bridge much as it is for local trail access, the future CCT through traffic will not be using the bridge.

But more can be done to improve the one block of Talbot Avenue that leads up to the bridge. Motor vehicle traffic is faster and more intimidating on Talbot Avenue than on the bridge. A sidewalk should be planned along the west side of Talbot Avenue from Lanier Drive to the stop sign at the end of the bridge.

The CCT can work with the proposed new alignment.

I regret that this post is so long, but there are many issues to consider in this new MTA Purple Line plan. I believe that when everything is considered, there are fair trade-offs. The CCT can work about equally well under either an alignment on the north side or south side of the Purple Line in the Lyttonsville area – provided good attention is paid to the trail and local access as the design progresses. The MTA has made a reasonable case that the proposed change will make the Purple Line work better. Trail users and the community should give the MTA proposal fair consideration.