My Opinions Regarding Single-Tracking
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NOTE: This page is an old page created when the Seattle Monorail Project was still alive. I have made some revisions in this page, but it may still refer to the Project as if it were still active. However the ideas expressed in this page apply to any future project. The Seattle Monorail Project’s latest plans included “single-tracking” some parts of the line.The original design was for the entire line to consist of two guideways (beams) for the trains to run on, with trains going in one direction using one guideway and trains going the opposite direction using the other guideway. Toward the end of the project the SMP was proposing to use a single guideway in places in order to cut costs and to reduce visual impact on the neighborhood. Switches at each end of a single-tracked section of the line, along with computer controls, would switch only one train at a time onto the single guideway and prevent trains going opposite directions from colliding. Cost savings would not only be from having one less guideway to pay for. A single guideway would also permit less complex and lighter-duty pylons (supporting columns) and less expensive foundations. Maps of the new plan show double-tracking in the central portion of the line with single-tracking further out where a lower train frequency could be used. There would be single-tracking in some of the outlying neighborhoods with double-tracking around the stations. I think that the plan would work, however I am opposed to the single-tracking concept for two basic reasons — safety and future planning. The safety issue is simple. Anytime you have the possibility of two trains running in opposite directions on the same track (or guideway in this case) there is a risk of a catastrophic collision. This system is going to use the most modern and sophisticated compouter system that should eliminate any chance whatsoever of two trains from opposite directions from getting switched onto the same same guideway. There would be very thorough testing of the system before it goes into service. I really doubt there would ever be a collision. But computers can fail and people can make mistakes. Even though the risk of an accident would be extremely small, the result of two trains colliding head-on at a high speed would be so devastating, with potential loss of hundreds of lives, that I don’t think we should take the risk, no matter how slight. The other factor is future planning. The single-tracking would have helped the Monorail Project meet its goal of having the first part open for business on December 15, 2007, and to do so despite unexpected reduced revenue from automobile licensing taxes. However I am less concerned about meeting goals as I am about the ability of the line to handle future ridership and expansion. POPULARITY: I anticipate that the line will be more popular than expected. I think that once the line is in operation and people find out how much faster and dependably they can get to work or school, many will use the monorail rather than drive. NORTHGATE EXTENSION: I also anticipate that the north end of the line will be extended about three miles to the Northgate area; which contains the big Northgate Mall shopping center; North Seattle Community College; Northgate Transit Center, a major regional hub for bus lines; large parking lots which can be expanded to provide park-and-ride facilities for monorail riders; and a large number of stores, businesses, and offices. All this means that there will be a major destination at the end of the line and result in greatly increased ridership in the northern part of the line. MONORAIL-INDUCED DEVELOPMENT: Completion of the line will almost certainly result in the construction of more apartments, condos, and businesses along the line, further increasing ridership. FUTURE SEATTLE MONORAIL PROJECT LINES: The Green Line is only the first of five lines proposed for the Seattle system. As other lines are built and interconnected, the overall effectiveness of the entire system, increasing ridership on the Green Line. SUBURBAN LINES: There are groups proposing other monorail lines outside of Seattle, especially Citizens for King County Monorail, that would interconnect with the Seattle system. One of their lines would come from Bothell and connect to the Green Line in Lake City or Northgate. I also consider it likely that there will be efforts to build a line north from Seattle through Shoreline and Edmonds to Lynnwood. Addition of these new projects would greatly increase ridership on the Green Line. The Seattle Monorail Project says that in the outlying areas the trains on the Green Line would run about every six minutes, and this would be far enough apart that a northbound train would pass through a single-tracked section before the next southbound train would enter the section. But if ridership grows too much, the simplest way to handle the increased load will be to run trains more frequently. Perhaps with a five-minute headway (the time between trains) the single-tracking will still work. Maybe even with a four-minute headway. But as you reduce the headway to three mionutes or less, at some point you will encounter the situation where there is not enough time between trains for a northbound train to get completely beyond the single-tracked section before it is time for a south-bound train to enter the same section. In other words, single-tracking destroys the flexibility to run trains as frequently as required. In order to convert a single-tracked section to double-tracking, the line would have to be shut down for probably a few months while the conversion takes place. And it would not only be a matter of adding a second guideway. The Monorail Project indicated it intends to save cost by using smaller pylons to support a single guidway. So replacement of a single-tracked section with double-tracking would mean removing existing pylons and replacing them with heavier foundations and pylons. So my opinion is that saving money now by single-tracking is penny wise and pound foolish. To me it is cutting corners to meet more immediate goals at the risk of heavy expense and major disruption of service in the future in order to make the line suitable for the needs of that time. I feel it is much better to build the line now to standards that should suffice far into the future, which means building a dual guideway over the entire length of the line. As for the matter of working with reduced revenues, I think the solution is to revise the system of taxation to meet the needs. Click here to read about my opinions about taxation. |
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©2002 Robert M. Fleming Jr.
This page was last updated 17 April 2007.