Several residents from Chevy Chase neighborhoods near the Georgetown Branch Trail spoke against the double track Purple Line in the Functional Plan at the Dec. 10 Planning Board public hearing. They argued that double tracking would greatly increase the impact on the Trail over the single track trolley approved in the first Georgetown Branch Master Plan, and that it was an unfair ‘bait and switch’ to change the master plan to a double track system now when the original plan was for only a single track trolley.
You only have to lift the curtain a little to see how uninformed this argument is.
Would removing the second (right side) track make a big difference?
Single tracking is not as important for a good trail alongside light rail as are several other design practices. The trail with rail shown above has about the same separation distance between trail and rail as would the Purple Line in the Georgetown Branch corridor. The presence of the second track on the right side of the photo can hardly be noticed from the trail compared to the other aspects of the design including the buffer between the trail and transit, the grass tracks, and the transit vehicle.
There are several features of single tracking that would greatly limit any real benefits to trail users:
1 – The Purple Line would be single tracked only for a short section between the transit platforms at Bethesda and at Connecticut Avenue.
The section of the Georgetown Branch corridor proposed for single tracking is only a distance of about 0.9 miles. It cannot be single tracked at or near the transit stations for operational reasons (the vehicles must be able to pass each other at stations). One of the speakers at the public hearing complained that double tracking greatly complicated the problem of bringing both the trail and light rail through the constrained space in the Bethesda Tunnel. But light rail has always been planned as double track in the tunnel. The 1996 Preliminary Engineering Drawings for the Georgetown Branch show the so called “single track” trolley as having double tracks in the tunnel at the station platform, and also east from the tunnel for 580 feet until the tracks merge. All of the issues of how to fit two tracks and a trail through the Bethesda Tunnel must be dealt with, regardless of any decision about single tracking between stations. The Georgetown Branch trolley station at Connecticut Avenue has a similar double track section leading to the platform, as shown in the 1996 Preliminary Engineering Drawings. The double track extends for 1000 feet west from the station platform over Connecticut Avenue to the vicinity of the first County Club putting green and tee, and also 1000 feet east from the platform.
2 – Single tracking will not increase the width of the buffer between trail and rail.
The single tracking is being proposed to save trees in the Georgetown Branch corridor and to keep the transit tracks as far from adjacent properties as possible. These goals require minimizing the width of the total transit and trail profile, and cannot be met if the space “saved” by single tracking is put back into a wider buffer between the trail and the transit tracks. It is extremely unlikely the residents of Chevy Chase who are raising the single track issue will let the ‘benefit’ of single tracking go to increasing the trail buffer instead of to increasing the buffer between their homes and the Purple Line.
Source: MTA 1996 Georgetown Branch Preliminary Engineering Drawings
The sketch above shows the old proposed Georgetown Branch Trolley at a typical single track section. Note the distance between the center of the tracks and the edge of the trail is 18 feet.
By comparison, the distance between the center of the nearest track and the edge of the trail for the proposed Purple Line typical section above is 20 feet. The distance from the trail to the nearest track is virtually identical for both the older Georgetown Branch trolley single track concept and the Purple Line double track concept. The Purple Line typical profile shows several transit design “best practices” that are not in the older Georgetown Branch Trolley plan – the planted buffer, an elevation difference between transit and trail, and a fence. Not shown but also proposed is grass tracks. These will impact the trail user’s perception of the transit more than will the presence of a second track.
3 – Single tracking would spare (at best) only a few trees.
The second track will add about 12 feet in width to a typical transit and trail profile over what single track transit would have. It is unlikely much of that reduced width will save trees during construction. When MTA studied this issue they concluded in their “Single Track in the Georgetown Branch right-of-way” report:
“While building a trail and single-track transitway would reduce the width required for permanent use by 10-12 feet, construction of that arrangement would still require clearing of most of that 66-foot width. As the trail would be largely at a different elevation than the transitway along the master plan alignment, construction of one track of the transitway would require access from the side. When building one track, the construction equipment would use the space for the other track and vice versa. Therefore, the hoped-for intent that building a segment of trail and single-track segment would reduce the amount of tree clearance from what would be required for building a trail and double-track segment not likely be achieved.”
That 12 foot reduced profile width would be available to replant trees after construction is completed. But the trees now in that zone will not be spared.
The MTA single track study also concluded that coordinating the safe movement of transit vehicles going in both directions on the proposed 0.9 mile long section of single track would create severe operational constraints that would reduce the level of service for the Purple Line. We have already experienced this with the failed effort to operate single track sections in the Baltimore light rail system.
Contrary to the assertions of Purple Line opponents that double tracking is an unfair bait and switch from the original single track trolley plan, double tracking was anticipated in the earliest master plan. Craig Simpson addressed this issue in the Purple Line NOW! testimony to the Planning Board. Purple Line NOW! reminded the Planning Board that the Georgetown Branch Master Plan approved in 1990 not only selected light rail, but also specifically states on page 49:
“In the event future consideration is given to implementing additional double track sections, the existing right-of-way is generally sufficient with appropriate structural treatment to accommodate the necessary typical 56-foot trolley/trail cross section (see Figure 4), except along the Metropolitan Branch section from Talbot Avenue to Silver Spring.”
The language “additional double track sections” appears in the 1990 Master Plan because the trolley was to be double track for as much as 1000 feet on either side of each of the five station platforms for operational reasons. This so called “single track” Georgetown Branch trolley was to be double track for over 1/4 of its 4.4 mile length, at all of the stations where some of the most severe design constraints exist. Assertions that to consider double tracking now for the Purple Line is an unfair ‘bait and switch’ from the previous plan are unfounded and uninformed.
Trail supporters should keep the focus on what is really important, and not get drawn into an off track single-track diversion from transit opponents in Chevy Chase. Eliminating the second track will have very little impact upon trail users but will cripple the Purple Line. Best practices in modern light rail design include grass tracks, landscaped and planted buffers, and using the new, quiet transit vehicles. These can do much more to maintain a pleasant trail environment than can single track.
Modern light rail is not like your grandfather’s trolley.
A tram in Montpellier – courtesy Harry Sanders
Many trail users join me in believing that given the Georgetown Branch corridor having been purchased by the county for future transit use, and also given the trail will be rebuilt to a high design standard and will be completed into downtown Silver Spring with the Purple Line, trail users cannot reasonably refuse to share this corridor with light rail. But regardless of whether we support or oppose the Purple Line, we should agree that when we do share the corridor we do not want to severely cripple transit by having a short single track section that gives us very little benefit. I want any accommodation trail users make to be for a fast and efficient transit system.
Tags: Future CCT plan
wayne, very good response here.
a number of the save the trail folks also suggested that another route be considered, primarily the BRT proposal on Jones Bridge road. As I pointed out it in my testimony, a BRT proposal is inferior to LRT on many factors such as ridership, speed, etc. including air pollution, which is one of their stated reasons against using light rail on the trail.