Single track rapid transit

[scratchyX1]

Baltimore's LRT was built so that they had a lot of single-track lines and headways of 7.5 minutes... but it was also built on pure politics and a floated bond. The bond's been paid back for quite a while, and they got Federal funding for double-tracking all the way up to a small section where there isn't much room for another track.

At the north end, where it's so bendy, the speeds are low.
And leading into the airport station.
And sadly now that it's double tracked... 7.5 minute headways are wishful thinking.

[Arborwayfan]

How long is the stretch of single track that could not be easily doubled? ROW including underpasses, culverts, etc., would fit double track as far as West Roxbury station. What about between the Needham stations? I'm just wondering if the OL could be extended out to Needham Hts with just half a mile or so of single track over the river and marshes. How long of a single-track segment maybe gauntlet track, even--could be handled without much effect on headways?

[ExCon90]

That appears to be manageable as long as there are two tracks with an island platform at the outer terminal.

[edbear]

The Needham Branch was once double tracked from Forest Hills to West Roxbury.

[HenryAlan]

How long is the stretch of single track that could not be easily doubled? ROW including underpasses, culverts, etc., would fit double track as far as West Roxbury station. What about between the Needham stations? I'm just wondering if the OL could be extended out to Needham Hts with just half a mile or so of single track over the river and marshes. How long of a single-track segment maybe gauntlet track, even--could be handled without much effect on headways?

Most proposals for Needham Line conversion to rapid transit do not include the Orange Line going much past West Roxbury. An infill station around the VA Hospital/West Roxbury Education Complex is sometimes suggested, but nothing beyond there. Needham itself would be served via a Green Line spur off the D-Line. Not sure exactly what Tallguy has in mind, but I don't think any proposal for the OL to cross through Cutler swamp is likely to go anywhere.

[wigwagfan]

A lot of LRT lines are built with substantial sections of single track, with the possibility to infill later. I know portions of the Baltimore and Portland systems were built that way.

The only portions of Portland's MAX system that were single-track WAS the easternmost portion in Gresham (long double-tracked), and some short stretches of the Red Line (Airport Line), but since that line operates at most a 15 minute interval service it's of little consequence. At most I've had to hold at a red block for a minute or so, no more different than another station stop (or some idiot holding the doors, or a ramp request, or downtown congestion, or cars blocking the track). I've had longer delays caused by Fare Inspectors.

[Bob Roberts]

Terminal stations are what I am looking for. Working with some college students on possible OL extension in Boston.

The Norfolk Tide system has single track terminal stations. It appears this design choice was made to save the cost of building a second platform since the single track sections are quite short.

[lpetrich]

New Jersey Transit has several heavy rail lines with many miles of single track, with passing sidings here and there along the way.

Are those commuter-rail lines? Single track is common in commuter-rail lines, even if not in urban heavy-rail lines.

[Disney Guy]

I don't know of any operating examples but I envisioned a rail transit line with a single track section at the far end. Depending on train spacing outbound approaching the single tracked section, some trains (maybe every other train) would short turn without going to the far end. Passengers on a short turning train would simply board the next train. There would be provision for ad hoc short turning of trains notably if bunching occurred coming outbound.

Some sites may lend themselves to fewer short turns if, should bunching occur, a train going to the outer end began its inbound run early instead of on schedule. Another possibility is a tail track (could be just one) to store an extra train to fill in inbound for a delay of trains coming outbound.

I thought that such a single track system could work for an extension of Boston's Orange Line past Forest Hills where there isn't room for two new tracks for rapid transit. Even just to Roslindale Village (one mile, one more stop) would eliminate a lot of buses from congested Washington St. although the extension would need land for a bus staging area at the new proposed terminal.

[R36 Combine Coach]

I don't know of any operating examples but I envisioned a rail transit line with a single track section at the far end.

SEPTA's Media (101) Line, single track in downtown Media on the west end. During weekday peak, some cars short
turn at Woodland Avenue (Springfield) which is the end of double track.

[andrewjw]

Zurich S10 runs every 20 minutes including substantial single track. Until last year, this included a section next to the S4, also single track at the time, and also every 20 minutes, in which each line used segments of the other's line as its passing loops! (That section is now double-track shared because the S10 has been upgraded to AC traction.) That's more frequent than the 101, which is every 30 minutes.

[Literalman]

Woodland Av, the end of double track on the Septa 101 line: there's also a passing siding at the east end of Media, from approximately Beatty Rd to Providence Rd. I live in Drexelbrook and ride the 101 a lot. But, yes, double track per se ends at Woodland Av.

[HenryAlan]

I thought that such a single track system could work for an extension of Boston's Orange Line past Forest Hills where there isn't room for two new tracks for rapid transit. Even just to Roslindale Village (one mile, one more stop) would eliminate a lot of buses from congested Washington St. although the extension would need land for a bus staging area at the new proposed terminal.

There actually is enough room to accommodate an Orange Line extension, though I agree it's tight, so long as the Needham Line is still running parallel to it. For bus staging, one of the two parking lots at the current commuter rail station could easily convert. Those lots are underutilized, and would be more valuable as part of a transit staging area.

[jbvb]

Take a closer look at the Needham line in aerial photos. Gardner St., the Charles River bridge and the bridge over the stream west of the Charles River all have abutments for two tracks. It's hard to tell about Greendale Ave. Great Plain Ave. has room for two also, but they built the passenger platform on the outbound track's roadbed. Then double track RoW all the way to Needham Jct. The only thing that isn't double track is the Rt. 128/I-95 underpass. There the alignment in use appears to be the former outbound track.

So no new fill across the swamp, just ballast and track. Which will likely get some resistance, but not well-founded...