(Another version has been cross posted at Greater Greater Washington.)
February 27 update: MTA has released its single-track operational analysis study and report to the County Council and other interested parties today. Unless experts can find major flaws in the study, I think we can put this issue to rest.
This blog has followed the evolving plans for the CCT and the Purple Line at the Bethesda Air-Rights Tunnel with numerous posts in the Bethesda Tunnel blog thread. Planners have been struggling with the rising cost estimates for keeping the CCT in the Bethesda Tunnel on an overhead structure above the Purple Line, and have requested the MTA look at alternative approaches including: 1) moving the Bethesda station platform east of the tunnel; 2) moving the platform to be under a new, redeveloped Air-Rights Building; and 3) using variations of platform locations that use reduced width track profile in the tunnel, i.e. single track or gauntlet track. The MTA has just submitted a draft of its study findings to the County Council, CCT Tech Report_20120224, and the Council T&E Committee is scheduled to take the issue up in a March 1, 2012 worksession.
The report findings are a disappointment to those of us who had hoped we could escape making a very hard decision. All of the new alternatives would seriously degrade the level of service and operational capabilities of the Purple Line or would have unreasonable cost.
I can quibble with some parts of the MTA draft report – for example MTA’s analysis of the three reduced transitway width alternatives :
…All three of the reduced transitway width alternatives yielded very similar performance results in operational simulations. None of the three will enable the Purple Line to operate at the six-minute headway required to carry the peak period passenger demand. With substantial portions of the Purple Line operating in street-running conditions subject to traffic interference especially at intersections, the train operations need to be able to have a schedule recovery time at terminal stations, including the Bethesda Station. The operational limitations imposed by these reduced transitway width concepts at the Bethesda Station would not allow for this recovery time, which would severely reduce the reliability of the service for the entire Purple Line. Therefore, due to these fatal operational deficiencies, this family of alternatives was eliminated from further study.
This analysis would apply to the CCCT single-track proposal as well. But the MTA draft report gives no information on the method and assumptions used for the operational simulations. While I may not be qualified to judge the technical merits of the simulation, there are interested parties in M-NCPPC, MCDOT, and in the trails community who can. I will feel more comfortable accepting the MTA conclusion if they make the operation simulation available for review. In fairness, this is an early draft report and perhaps the final report will show more. In any case I reluctantly think they are probably right on this. I can find no examples of successful single-track operations for a terminal station with a short headway requirement.
As much as I wish it were otherwise, we are back to the hard choice: either spend a now estimated $50.9M and take considerable construction risk to keep the trail in the tunnel in an overhead structure, or develop the alternative surface route across Wisconsin Avenue.
For me the right choice is to develop the alternative surface route to the fullest extent possible. $50.9M is simply too much money to spend to avoid one at-grade crossing for the trail. That cost will double the total cost of rebuilding the CCT, putting the whole trail project at much higher risk of being abandoned in these very difficult budget times. As I observed at Taking a hard look at the tunnel I don’t think the switchback and cage on the tunnel route will be attractive to most of us, certainly not inviting enough to justify spending $50.9M. There is also too much risk that digging under the APEX building will destabilize the entire building. I’m still in shock at seeing our long transit center nightmare in Silver Spring because engineers underestimated the risk of a construction method. I don’t want another mess like that along the future CCT in Bethesda.
I think it is likely the Council will decide against accepting the cost and risk that comes with keeping the CCT in the Bethesda Tunnel. The political blowback from this decision will be intense, you can already see some of that in the comments to the Washington Post story Planners reject proposal…. “Save the Trail” advocate Pam Browning and others are advocating for a third option, i.e. kill the Purple Line. But they have the Tunnel Vision that comes with thinking that CCT means “Chevy Chase’s Trail”. They care little about whether the CCT is ever completed into downtown Silver Spring, and would have us obsess about one trail crossing at Wisconsin Avenue while overlooking the many other at-grade crossings and the on-road trail route we continue to deal with east of Bethesda.