Bicycling
The Capital Crescent Trail should stay in its Bethesda tunnel
Last week, Dan Reed argued that an on-street Crescent Trail may be better for cyclists and pedestrians. But not putting the trail in a tunnel represents a huge downgrade of bicycle infrastructure, and the MTA should find a way of fitting the trail in the tunnel with the Purple Line.
Photo by M.V. Jantzen on Flickr.
For a year or so I commuted through that tunnel almost every day and have been an occasional user since it opened. It is an excellent cycling amenity, providing a shorter, quicker, safer and more convenient route through the heart of Bethesda.
In his post last Friday, Dan suggests that putting the trail on the street may be safer because the tunnel might attract criminals. He points out crime problems at other bicycle and pedestrian tunnels. In this case, the tunnel has been open since 1998 and crime has not been a problem. More activity makes crime even less likely. The danger of crossing Wisconsin Avenue at street level is greater than the risk of crime.
It makes no sense to eliminate an excellent grade-separated facility that already exists in order to get drivers to understand that bikes "belong" on the street. Plus, with an improved trail to Silver Spring will likely increase the number of cyclists in the Bethesda area. Cyclists in the area will use the streets to get to and from the trail. The better the trail, the more will use it, and the more street traffic there will be.
In the '90s, cyclists fought long and hard to get the tunnel opened because it was a terrific alternative to the on-street routes. It was an enormous success and trumpeted in the biking community. The Coalition for the Capital Crescent Trail not only supported the tunnel opening, but contributed thousands of dollars of funding to help make it happen. Clearly the biking community prefers the tunnel to the on-street routes.
It seems unlikely that one would argue to eliminate the Custis Trail through Arlington or the W&OD trail through Falls Church in order to put more bikes on the streets. But Dan thinks this is a good idea in Bethesda.
Amsterdam underpass. Photo by Brent Granby on Flickr.
Creating cycling facilities like those found in Copenhagen or Amsterdam, including grade-separated facilities like the one shown here, makes it better for cyclists, and more cyclists are everywhere, creating a better atmosphere all around. Those cities did not achieve their high biking mode share by eliminating grade-separated crossings.
Boulder, CO has added 20 new grade-separated crossings in the last 20 years, and cycling has gone up, not down. And there are lots more cyclists on the streets, too, not just the trails.
Minneapolis's new Greenway is celebrated as a fantastic success for cyclists and pedestrians. Cycling and pedestrian traffic has increased in Minneapolis as well.
Current estimates indicate that keeping the trail in the tunnel with the Purple Line will cost $40 million. Even at that price, the trail is worth the cost. However, the Maryland Transit Administration is undertaking detailed studies to determine whether the cost could be lower. The Montgomery Planning Board has also asked them to study alternative ways of fitting the trail into the tunnel.
The shortest on-street alternative to the Bethesda tunnel adds about 400-500 feet to the trip. (The longest adds about 1,500 feet.) The shortest on-street detour also entails a 30-foot elevation rise and fall and a major road crossing that will require a wait at a signal.
This route is likely to add at least 1 minute to any cycling trip, costing as much 10,000 hours per year cumulative for cyclists and peds (at current usage rates, before increased traffic when the trail is completed to Silver Spring). In addition, auto traffic will also be delayed by longer signal cycles to accommodate trail traffic. Some might argue that is good, but it's time lost, nonetheless.
Should Montgomery County propose closing lanes and parts of streets and eliminating parking in order to create this route, they are likely to receive pushback in the public process from drivers and businesses. Officials will likely end up scaling back the design as a compromise with opponents.
There's no guarantee that the alternative on-street route will end up with good design and execution. It could very well end up a lose-lose for cyclists and pedestrians: the tunnel option could be eliminated, and the on-street alternative could be adequate instead of excellent.
The Capital Crescent Trail in Bethesda is equally as busy as the the Custis Trail through Rosslyn. There are approximately 23,000 weekly users on CCT and, according to Arlington County staff, about 26,000 users on the Custis Trail.
Building an at-grade crossing at Wisconsin may end up creating as big a problem as the Custis Trail/Lee Highway crossing. That intersection is a huge headache for planners there and a significant hazard to users. Admittedly, the Bethesda on-street routes do not suffer from the same design issues as the Arlington one, and it would likely be easier to make safer.
Should the cyclists and pedestrians lose this battle, it will once again send the signal that they are are lower-priority citizens. Cyclists showed up in droves a couple of years ago to keep the tunnel open during the upcoming development by JBG and, with the help of Councilmember Berliner, were able to win that concession from the developer.
Prior to that meeting, though, the county was intending to go along with the developer's plan to close the tunnel during construction, an option that would never be considered for a similarly important automobile route. Until the cyclists spoke up, the developer's needs were put ahead of them.
This is an almost identical situation: a proposal is being made to close the trail in the tunnel to accommodate development. Fortunately, this time, it appears pedestrians and cyclists are being given more consideration. A few weeks ago, the county planning board toured the tunnel and, according to the Washington Post, the board was very supportive of finding a solution to keep the trail in the tunnel.
Dan suggests that taking the trail out of the tunnel will make this a "better experience." Given the strong support, including actual financial contributions, from the biking community for the tunnel, it seems that most cyclists feel the tunnel is the better experience.
When I was commuting from Arlington to Silver Spring, I wanted to get home, not browse shop windows. I couldn't wait to arrive at the tunnel during the dark winter nights, and it made for great shelter during summer thunderstorms.
But other times when I was actually visiting somewhere in Bethesda, I could choose to proceed directly to my destination on the streets. The existence of the tunnel does not preclude cyclists and pedestrians from accessing local businesses. In fact, a superior facility is likely to attract more people to the area, which would be good for local businesses.
Lastly, on a per-user basis, my back-of-the-envelope calculation indicates that the per-user cost of the Purple Line is actually higher than the per-user cost of the trail with the tunnel, and that doesn't include operating costs. With 60,000 estimated daily Purple Line in 2030 users and a cost of about $2 billion, the average cost per daily user is $33,333. The trail, on the other hand, is expected to cost about $100 million and handle about 4,000 daily users. That makes the average cost per daily user $25,000.
Keeping this excellent piece of the regional bike infrastructure is critical to the ongoing growth of cycling and continuing to improve Washington's standing as a good biking area. As Dan writes, the trail has been included in plans for the Purple Line for more than 20 years, including the tunnel portion, which shouldn't be eliminated to save a few dollars that no one will remember a decade from now.
 | Steve Offutt has been working at the confluence of business and environment for almost 20 years, with experience in climate change solutions, green building, business-government partnerships, transportation demand management, and more. He lives in Arlington with his wife and two children and is a cyclist, pedestrian, transit rider and driver.   |
Comments
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A good street level crossing would be fine by me.
by Capt. Hilts on Nov 25, 2011 1:57 pm • link • report
So far, the debate over the tunnel has focused on cost and the trail experience with the tunnel vs. the trail experience without the tunnel. There is, however, another key reason why it is imperative that the path stay in the tunnel: government accountabillity. Many Purple Line opponents (and just plain skeptics) have been very concerned about the MTA pulling a bait and switch: that is, making certain representations (regarding cost, ridership, noise levels, the ability of the PL and trail to actually fit within the ROW, and the compatability of the trail and the rail, to name a few) in order to garner political and public support for this project, only then to back away from those representations once enough support has been secured to keep the project going. And that may very well be what is happening here. The MTA all along has assured the public and the County government (somewhat cavalierly, perhaps)that the trail and rail could tunnel under Wisconsin Avenue. Now that the project has graduated to the preliminary engineering phase, all of a sudden the MTA says, "gee, it looks like keeping the trail in the tunnel will cost you an extra 40 million bucks." The bottom line is that our elected officials need to hold the MTA's feet to the fire, and make them deliver the Purple Line and CCT as promised. Otherwise, the slippery slope begins, and you'll be appalled at the many other representations MTA has made that turn out to be pure fantasy.
As for those who think the at-grade crossing is "good enough," that is an opinion certainly entitled to respect (indeed, it was my initial thought too), but even that option will prove much more complicated than it appears at first glance. For example, if you expect to have signal priority at Wisconsin (or bike only lanes), good luck. Those sorts of measures need to go through the State Highway Adminstration, not MTA or Mont. Co. I think you'll have a tought time getting SHA on board with those ideas.
by BS_Dawg on Nov 25, 2011 2:28 pm • link • report
Will you still feel like the tunnel is so good when you see the new route for the trail in the overhead? There will be a tortuous swictchback ramp at the west end of the tunnel, that will be built into the back side of the JBG bldg. It will require that all cyclists dismount and walk up the ramp. Riding up the gentle incline on Bethesda Avenue to Wisconsin Avenue will seem easy in comparison. See http://www.silverspringtrails.org/?p=1736 for the plan for the switchback ramp.
I hope we can find a way to keep the trail in the tunnel. But we will need to develop the alternative street route as extensively as possible whether the trail stays in the tunnel or not, because that is where most cyclists will want to ride after they get a look at that ramp.
by Wayne Phyillaier on Nov 25, 2011 2:31 pm • link • report
Thanks for your response to my post last week. I did say that there might be issues with crime in a tunnel, and it's good to hear that it hasn't been a problem in Bethesda.
But if crime in a tunnel isn't a given, why is "opposition" to building an on-street route a given? The Bethesda Sector Plan already proposes what is essentially a cycle track on Bethesda Avenue. Sure, a few parking spaces would be lost, but that pales in comparison to the 1100-space garage being built at the corner of Bethesda and Woodmont avenues.
As Wayne Phyillaier points out, building a new trail in a tunnel over the Purple Line would require users to mount a big switchback ramp and go down a trail with as little as 8' clearance. That's roughly the height of a hallway in a typical house. Is that really a superior experience? I don't think so. It certainly won't be anything like the current tunnel experience.
Your argument for the tunnel still doesn't address the issues of what happens on the street. There are no bike facilities in downtown Bethesda other than the CCT and short bike lane on Woodmont Avenue. Is it really appropriate to spend $40m to build a short tunnel when bicyclists going anywhere else in downtown Bethesda have to contend with big, fast streets like Wisconsin Avenue? That certainly won't encourage people to bicycle more. And it'll give non-bicyclists more reason to say, "Well, we gave them a tunnel. Why bother doing anything else?"
They say don't let the perfect be the enemy of the good. As a bicyclist, I'd rather have a good on-street trail network in Bethesda (not to mention the CCT extended to Silver Spring) AND a Purple Line built as proposed rather than one really good tunnel and nothing else. I hope the area bicycling community can come together around a vision of good bike facilities across the board rather than fighting for one gold-plated tunnel.
by dan reed! on Nov 25, 2011 2:31 pm • link • report
Are you saying that it's worth running the cycle track through the tunnel at any cost?
Okay, so you like the tunnel a lot. It probably saves you a minute or two relative to an at-grade crossing--or would, if you still used it. Also there's another trail that has a problematic at-grade crossing, though you say it's not really comparable. Oh, and any change to the trail might hurt cyclists' feelings.
For those reasons, this way of spending tens of millions of dollars is better than any other? I'm not seeing it.
by Gray on Nov 25, 2011 2:55 pm • link • report
As far as the switch back goes, I don't think it is going to be worse then the switchback to the GW Bridge in NYC:
https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc6/251661_10150200770203076_513493075_7009803_6410121_n.jpg
I'm not saying it's going to be great, but it is not a 100% negative either. And that's another thing that bothers me, all options so far seem to degrade what we currently have.
by Barry Childress on Nov 25, 2011 3:52 pm • link • report
The two methods of keeping the trail in the tunnel that the Planning Board suggested studying would add one to four minutes walk time to most of the 23,000 daily trips (weekday) that begin or end in Bethesda. That adds up to between 100,000 and 400,000 hours per year of delay.
And the 10,000 hours per year delay for the at-grade trail is a great overestimate. It does not subtract the delay in going through the tunnel after the Purple Line is built, due to the need to go up the switchback to enter.
Moreover, 4,000 riders per day is a vast overestimate. This number was counted south of Bethesda Avenue, not at the tunnel. The number on the trail at the east entrance of the tunnel was 60% lower. Also, the counts were taken on days of good weather in September. The year round average at these locations is much lower.
by Ben Ross on Nov 25, 2011 4:14 pm • link • report
by Ben Ross on Nov 25, 2011 4:15 pm • link • report
I can't agree. Given the required changes in the trail geometry to keep it in the tunnel as well as the increased cost, and given the relative quality of the alternative surface route, I don't see any rational way to support the trail in the tunnel alternative.
What's the purpose of keeping the trail in the tunnel if the required changes mean you lose a great deal of the benefit of that grade separation in the first place?
by Alex B. on Nov 25, 2011 5:01 pm • link • report
More than 50% of the users at CCT and Bethesda Ave. were pedestrians. Personally, I am more likely to take the streets when walking than while on a bike.
by Jim Titus on Nov 25, 2011 5:59 pm • link • report
by Falls Church on Nov 25, 2011 9:46 pm • link • report
Ok State
Virginia Tech
Stanford
Boise State
Houston
First I'm going to point out that we don't really know the cost of keeping the trail in the tunnel. Maryland said it could be as high as $40M, but they don't know yet. Personally I wish they'd kept their mouth shut until they knew the actual number. If it comes down to $10M, some blowhard will still be out there talking about the $40M trail tunnel, even if MoCo decides against it. Anyway, this is kind of an academic arguement until we know the real price.
Are you saying that it's worth running the cycle track through the tunnel at any cost?
Steve seems to be saying that any cost is worth it.
I don't think he does. He says the purple line costs $33,333 per average daily user and the tunnel is $25,000 per average daily user. So, one can conclude that if $33k is reasonable than $25k is even more reasonable.
The problem with this is that if you don't build the Purple Line you'll have 0 users. If you don't keep the trail in the tunnel, you will have some reduction in trail users, but it will be less than 100%.
It is a question I've asked before, and it is worth asking again (since no one gave me a number) what would be the right price? When would Steve think it was too much? $100M? When would Dan think it was not too much? $10M?
Imagine that there was no tunnel today and you had $40M to spend on bike facilities. Would you blow it all on one tunnel or are there other more productive projects you would undertake instead?
That a good exercise and no one would, but it's not accurate. If the county spends the $40M on the tunnel, there will still be money for biking (and pedestrians let's remember). In fact, I suspect that the money spent on biking/walking will go up when the tunnel is built as money will be pulled in from other budget areas to make it work. But it would be nice to see an opportunity cost analysis. If the county said to cyclists "We'll keep the tunnel, but we'll pay for it by cancelling this, postponing this by a decade, reducing these expenditures by half for a decade, etc..." it would be interesting to see who would balk.
by David C on Nov 25, 2011 11:31 pm • link • report
by David C on Nov 25, 2011 11:32 pm • link • report
I don't this this discussion has been argued well in these posts.
- the idea that grade separation is bad and we should put bicycles back on the street so people know about them is crazy. Should we do the same with rail transport? Obviously not. I am very comfortable riding on streets but I love a grade separated route, esp. if it is well engineered. I believe that if you asked regular cyclists to compare a direct separated route and a direct on-street route, 80-95% would prefer the separated route.
- The crime argument is silly too. I love the MBT but the fact is that it goes though some areas with real crime, and not just on the MBT. See FL Ave & N Capitol, where there is lots of street activity and real crime problems.
- Nevertheless I am confident that many are uninterested in riding through the current tunnel at other than peak ridership times. In the future it will probably have more riders and be less pleasant if it gets relegated to a giant PVC pipe suspended over the tracks. A quick way to get through town, yes, but rather unpleasant and likely to be perceived by some (or many) as unsafe or creepy.
- This decision does not set precedent nor should it be turned into a morality tale about our government.
We need to look at this in a straightforward fashion. Is it worth spending $40 million to keep me from having to cross Wisconsin at grade on my bike? I don't think so. Even if I take the ridership figures from the post as a given, comparing the per rider capital cost of the Purple Line from Bethesda to Silver Spring and beyond (I don't recall how much the $2B figure includes) to the bike tunnel under Wisconsin Ave. frankly just makes proponents of the bike tunnel look ridiculous.
And now we hear talk of stopping the Purple line short to save the bike tunnel? That, my friends, is INSANE.
I will probably use the bike trail about as much as I use the purple line, or a little more. I live to the east so I have far more to gain from the new bike trail east of bethesda (grade separation) than I will lose in downtown bethesda.
Lets stay pragmatic and get the purple line built with a functional trail next to it (except in downtown Bethesda, where we can deal with a traffic light or 3).
by David Duck on Nov 26, 2011 9:53 pm • link • report
While I don't agree about the safety issue (the Forest Glen ped bridge isn't in a rough area, and there were issues with crime there), I actually agree with your statements. I would correct one thing, though: I don't think we should put the trail on-street just to make people aware of bikes (though in MoCo, where most people drive, it's important to raise awareness of biking as a legitimate form of transportation), but it's still a desirable by-product of putting the trail on-street.
Having to share the road with bicyclists might encourage drivers to slow down (which they should be doing in downtown Bethesda anyway), which in turn makes it safer and more attractive to bike on the street.
by dan reed! on Nov 27, 2011 11:27 am • link • report
I really like the "redevelop the Air Rights building" approach from the WashCycle:
http://www.thewashcycle.com/2011/11/planning-board-investigating-all-options-for-cctpurple-line-tunnel.html
Maybe we can even get a second Metro exit out it, and integrate Metro with the Purple Line better.
But short of that, a surface route for the trail really isn't that bad -- it might even be better!
The key is to close Bethesda Ave to cars between Woodmont and Wisconsin (except a for small driveway to that parking garage – limited to the north half of the western third of that block). If the MTA wants to save $40M, then they'll just have to get the State Highway Administration on board -- that's the condition.
The new route should have dedicated bike signals at Woodmont and Bethesda Ave. We'd be trading an easier crossing at Woodmont for one extra light at Wisconsin. Currently you have to wait twice at Woodmont, first to cross Bethesda Ave then to cross Woodmont. Once we redo the sidewalk (on the north side of the parking lot that's on the SW corner of that intersection), you could ride directly on a dedicated surface, and get a single shorter signal, since the only permitted left turn for cars would be from Woodmont onto Bethesda Ave.
At Wisc Ave, we should prohibit left turns from Willow Lane onto Wisconsin, and no right-on-red from Wisc onto Willow, so bicycles would never face any turning traffic at all -- the opposite of the Lee Highway crossing. Remove parking to create dedicated lanes east of Wisconsin on Willow Lane (south side) and through Elm Street Park. There's a huge parking lot right there, no one needs those handful of spaces – the trail will draw far more customers to the farmer's market!
Result: equivalent distance compared to the tunnel, equivalent traffic safety to tunnel (dedicated bike-only route), better personal safety than the tunnel, easier crossing at Woodmont, better integration with street level retail. The only downside is the single additional traffic light with a dedicated bike signal at Wisconsin, with no turning traffic at all.
by Shalom on Nov 27, 2011 12:03 pm • link • report
"The key is to close Bethesda Ave to cars between Woodmont and Wisconsin (except a for small driveway to that parking garage... "
Cosing Bethesda Ave. to cars may not be practical, since there is a drive-through bank entrance and a small parking lot on the south side as well as the entrance to the parking garage in the office building on the north side.
But it is not necessary to completely close Bethesda Ave.. It is enough to remove parking on the north side to make room for a cycle-track and a better sidewalk on that side, and to prohibit left turns onto Wisconsin Ave. and right-on-red from Wisconsin Ave. so there will be no traffic turning across the Wisconsin Ave. crosswalk when pedestrians have the walk signal.
by Wayne Phyillaier on Nov 27, 2011 12:34 pm • link • report
Imagine that there was no tunnel today and you had $40M to spend on bike facilities. Would you blow it all on one tunnel or are there other more productive projects you would undertake instead?
This question hardly even qualifies as hypothetical. Once you show me the $40M--nay, just $20M, set aside in its own account for bike facilities, I'll start to think about it.
Right now though, it's build the trail in the tunnel for some cost less than $40 million max
vs.
some words, possible promises, likely problems with MD state highway officials and no guarantee that any more money will be spent anywhere else.
I'll take the first half of that equation. If the County wants to put aside 75% of the savings from not building the tunnel into a dedicated bike account, then it will be worth debating how much that is and what we get. Until then, your question is irrelevant, bordering on dangerously diversionary.
by Steve O on Nov 28, 2011 12:16 am • link • report
+1 !!!!!!!!!!!!
by Steve O on Nov 28, 2011 12:18 am • link • report
Here's one idea of mine. Disclaimer: I am not an engineer.
I think a modification of the single-track idea may solve a couple of problems at once.
Looking at the engineering drawing shows two platforms just west of Wisconsin Ave.
I suggest instead a single double-long platform on the north of the tracks and a switch that single tracks 1/2 way along the platform. The eastern half of the platform is for deboarding passengers, and the western 1/2 is for boarding passengers.
W-bound trains stop to deboard just before the switch. After deboarding they cross the switch and move to the end of the track. E-bound passengers now board here. When the train starts to move the other direction, it switches onto the track parallel to where passengers just deboarded.
This would allow for a 2nd w-bound train to arrive and deboard even while an e-bound train is boarding.
This solves a couple of problems:
1- the ugly switchback for cyclists/peds can be replaced by a longer, straight ramp in the tunnel on the space formerly required by the extra platform. This makes the whole experience for peds and bikes easier and more pleasant and saves the space that was required by the big switchback structure.
2 - costs are reduced, because a major part of the costs are for shoring up these columns. Since the trail does not have to be above the tracks for as far, fewer columns would need to be exposed.
by Steve O on Nov 28, 2011 1:10 am • link • report
The transit problem with your proposed solution is that now you've added two station stops where there used to be one (which ads time to any trip) and you've also got the entire transit line constrained by the need to operate on this one single track segment, even if it's a short one. That will negatively impact headways.
Conceptually, any single tracking is a non-starter in my book. It will substantially reduce the line's ability to grow capacity via increased headways. It will constrain the line's ability to extend further to the west.
Creative designs are good, to a point. They're only good if they respect the basic geometric rules of transit, and this would not (if I'm understanding your proposal correctly).
Practically, I don't think the idea of having the switch point be closer to the platform would be feasible. I don't think the existing column spacing would support such an alignment.
by Alex B. on Nov 28, 2011 9:09 am • link • report
by wd on Nov 28, 2011 9:27 am • link • report
Steve O's solution is not a zero cost solution, that's true. But then again, neither are any of the others. To say it won't work because it isn't zero cost is to ignore the costs of the other proposals.
by David C on Nov 28, 2011 10:15 am • link • report
Not being an engineer, I would have to defer to others on the details.
However, the trolleys have to switch tracks somewhere, do they not? I presume they travel on the right side in both directions, so a w-bound train has to switch back to the other track to travel the other way. The section of track where that occurs functions like a single track during the switch. My proposal just rearranges where that happens. The only part of the track that is single is the very, very end. Everything else remains double tracked.
(I noted that the e-bound platform is in between the tracks. How are passengers supposed to access it, I wonder?)
I got this idea from Houston, where their center platforms serve trains bound in one direction only, allowing them to be narrower so they can fit in the medians of downtown streets. Perhaps that same concept could be used here differently than I suggested, but reducing the width needed for the PL by the width of the platform, allowing the elimination of the ugly switchback structure.
My larger point, which I made first, is that bringing in some creative minds who are smarter than I am to look for out-of-the-box solutions at low cost (e.g. design contest) could reveal some innovative solutions. Let's give it a try.
by Steve O on Nov 28, 2011 10:18 am • link • report
Both platforms must be under the APEX building because there is no extra width for a platform under the Wisconsin Ave. overpass or under the Air Rights Building. Each platform must be 200' long and must be separated enough for the switch to be between their ends, so both platforms in a row would extend under the whole APEX building. The switch would be only midway under the APEX building, or only 200' from the west portal at best. The south track and switch would have to be fully depressed so the trail can fit overhead. The north track would also have to be fully depressed at the switch to match the elevation at the switch. The north side platforms must be level, therefore all of the north side track and platforms must also be fully depressed. The only part of the tunnel that would be spared digging to depress the tracks would be roughly 200' on the south west side of the tunnel. All of the north side and center columns would be undercut by digging.
So, the only columns that would not be undercut by digging would be the several columns on the south side of the tunnel, within about 200' of the west portal. So you reduce the cost from $40M to, say, $35M, and for that you must place a severe single-track operational constraint on the Purple Line.
I like creative ideas, but the geometry of the problem defeats this version of the single track as a useful solution.
by Wayne Phyillaier on Nov 28, 2011 10:37 am • link • report
Of course it would be easier, which is why this is a specious comparison. On the Custis you have 8 potential ways to cross Lee Highway, Fort Myer and Lynn. The CCT going across Wisconsin would likely have one way to cross.
by Fitz on Nov 28, 2011 11:04 am • link • report
The constraint isn't in the switching, it's in the turnaround time. The constraint of the single track means that you can only turn one train around at a time.
For a comparison, go to the end station of a Metro line during rush hour (say, Vienna, since there's no yard there) and watch how the trains turn around. They end up using both tracks in order to maintain the headways. That gives more than enough time for trains to turn around without blocking the ability of another train to enter the station.
A similar (but not completely analogous) situation is the Yellow line and its off-peak turn at Fort Totten. The reason you can't do this during peak hours is because it would interfere with the headways on the main track. What you propose would be operationally similar - using a lone single-track segment to turn trains would represent a severe headway constraint on the entire line. You might be able to make it work during initial operations, but what happens if demand requires shorter headways?
Even if that constraint could be minimized, it would still present a huge constraint to future expansion of the purple line to the west. It's a cardinal rule in this kind of infrastructure planning to never box yourself in, yet that's exactly what you'd be proposing.
I think Wayne hits on some of the trail-related issues, as well.
Bottom line: you have a series of constraints that can't easily be changed. ROW width, column spacing, and the space required for full operations of both the purple line and the trail. At some point, it's fitting 10 lbs of stuff into a 5 lb sack.
by Alex B. on Nov 28, 2011 11:53 am • link • report
by davidj on Nov 28, 2011 2:20 pm • link • report
There may be busy systems that have very short single-track sections along the line (like over bridges in Amsterdam as davidj points out in a prior comment). I know of one single-track at end-of-line for a trolley (in Media, PA) but that trolley has a very long headway at that location.
If we can find even one successful application of single-track at an end-of-line station for a system with short headways, our chances of getting the single-track idea taken seriously will be greatly improved. If no such example exits among the many working transit systems, then maybe there is good reason for that and we are pushing a weak idea.
by Wayne Phyillaier on Nov 28, 2011 2:58 pm • link • report
Commercial buildings are essentially temporary structures. We're trying to shoehorn 60-100 year infrastructure under a building that will be around for another decade or two at most (built in the late 80's).
So the PL construction (and trail) is made more costly and difficult by the Apex building. In 2025, construction of the new building will be made more costly and difficult by the existence of the PL. Doing both together 1)reduces the long-term total costs, 2)accommodates the trail more effectively, 3)makes future expansion easier, 4)allows for much improved design of the station, 5)allows for support infrastructure to hold a larger building and 6)creates more space by eliminating the switchback structure for the trail.
The final product for all users: transit, bikes, peds, plaza users, and developer, is superior.
Win win win
Work out a deal with the developer by offering some special zoning provisions to replace the building in conjunction with PL construction. Or not. The value of that property has just gone way up because we taxpayers are supporting the construction of new transportation right there. Have the property owner contribute, since they are freeloading off the public investment already. (I can hear the arguments on both sides coming already :) )
by Steve O on Nov 28, 2011 3:03 pm • link • report
In the abstract, I'd agree. But based on the constraints we have, redeveloping those buildings now adds a huge cost on to the project. I think that would be letting the perfect solution become the enemy of a good one.
As I said in my first comment, this is ultimately about a cost/benefit analysis. More analysis is needed, but I'm not convinced that keeping the entire trail in the tunnel is worth it. The trail itself will be degraded, and you can achieve a great portion of the benefit with dedicated surface routes and the option to add the full trail during the eventual redevelopment of the real estate air rights.
by Alex B. on Nov 29, 2011 3:02 pm • link • report
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