Bringing this conversation over to this thread since it isn't really about RUR.
Someone on twitter asked this very question so I showed them this response. The question that came up was what trains actually do this? The movement in question, if I understand, is a train coming from Cabot JFK and then reversing or a train going southbound to JFK and reversing to Cabot. But according to this chart (
https://t.co/zUMiswNRT1?amp=1) of all Red Line runs no trains actually do this. So this would suggest these are non revenue trains, correct? Then the question is would this not also be workable with three tracks at JFK with one converted to CR?
Is that an internal document or a train tracker data pull? I can't even zoom it down enough to see what all that tiny text is logging. Train tracker data pull can't differentiate between revenue and non-revenue moves because it's only pinging the lead car. As per the mystery appearance of the new RL car test set showing up "in-service" in the New Red/Orange car thread, the RFID tag pinged a lead car entering the mainline and logged a false positive. So you need a real internal operations log to tell what each set is doing.
If the preferred means of yanking into/out of service on
scheduled shift changes is a non-revenue run thru to Codman or Caddigan Yards at the ends of the branches, then the Cabot refills are accomplished in swarms of non-revenue movements between Ashmont-JFK and Braintree-JFK in between regular branch headways. Such that, for example, at the end of a peak shift you're going to have the 'traffic' of a peak headway upheld for some period after the rush shift ends as the non-revenue moves get slotted. You still need a hefty amount of slack capacity to do that, so cutting off one's nose to spite their face is not a real winner of a counterpoint.
In a delay recovery scenario they
definitely reverse on-platform @ JFK to scramble units into the subway...but that would not be reflected in a daily log because it's all on-contingency, and if it's a sample taken in the last 4 months with the reduced service you're not going to be seeing the delays to begin with because traffic is so much lighter that a disablement can get triaged without bunching. Beware your sample sizes.
---- ---- ---- ----
As mentioned in earlier posts JFK Station is
not the primary pinch point, so there is absolutely no reason to over-focus attention on infrastructure compacting at that site. Right then and there I have to wonder what's being proven by throwing out reams of charts as counterpoint, because JFK Station is begging for no reimagining. There is plenty of space to widen the CR platform into a 12 ft.-wide 2-track island off its current footprint by (1) reconfiguring the busways, (2) lane-dieting Old Colony Ave. for a few feet west where it's a glorified 4-lane wide/2-lane striped station driveway, and (3) replacing the little-used south RL headhouse which semi-obstructs the CR platform with a quick replacement that does not. That's it...the 2 extant RL islands don't even need a single touch, and anything that attempts to touch them is instantaneously going to be more expensive. Rapid Transit Dept. is going to correctly finger this as pointless Civil Engineering Strongman to try to force-fit only 2 RL tracks for integrity-of-concept's sake and zap their routing flexibility when there is no space shortage here compelling that move. Leave JFK alone on the RL sides, because the capacity solution here exists where there's currently little more than bare pavement.
Columbia Jct. to the north is easily compactable without sacrificing grade separation into the 2 JFK islands, by replacing the numerous space-intensive flyovers with simple crossovers and having the Cabot leads flank the sides of the portal to frame the start of the branch split. Columbia Jct. is as overbuilt as it is because it was 1960's-designed to facilitate high-speed (>60 MPH) South Shore service to Weymouth, Brockton, etc. outright replacing the RR mode. As soon as the line was drawn no further than Braintree, RR preservation + reactivated CR became the primary priority for points past 128, and the infill Braintree island was added to JFK...the flyovers instantly became obsolete relics. So half the space they take up can vanish, and the only thing that changes at JFK is that the 2 islands (beneficially!) change from Braintree IB/OB + Ashmont IB/OB layout to "all-inbound" + "all-outbound" layout. And then the flyovers to the south simply get modded in-situ to send each track of the branch splits on their merry way with the new directional alignment. Columbia compacting is simple enough unto itself with only that switcheroo of the south-of-JFK flyover set that you likewise would get your sanity questioned for trying to over-mod the JFK platform layout when no such squeeze calls for that.
Now...Savin Hill, the legit pinch point. You could, in theory, mash the 4 tracks back into 2 after JFK and stage the branch split further downwind. Technically that is available. Now here's why that would be non-preferred. To do so you would have to create
TWO more sets of interlockings: south-of-JFK re-mash, and south-of-Savin Hill re-split to go along with your much-simplified Columbia compacting. Rapid Transit Div. is going to howl about that, because heavily-used crossovers (like, for example, the Alewife "switching problems" from hell) are an outsized failure point amongst regular ops being pounded throughout the service day. Overbuilt Columbia is infamously called "Malfunction Junction" for the same reason. So you are going to increase the rate of faults to have the JFK split, the post-JFK re-mash, and the post-Savin Hill re-split tripling up a known failure point. The zeal towards saving a few topline bucks by at-gradeing everything at Savin Hill induces a lifetime ops tax for increasing the number of failure points in a short stretch. It'll make the shift changes harder because the equipment pipe will have to traverse the new failure points several times a day. And it'll compel as a "solution" the over-compacting at JFK to eliminate the extra interlockings for same proof-of-concept motivation that adds nothing but empty-calorie additional cost, such that the money wasted rebooting all of JFK eats the lion's share of the savings from doing that capped box tunnel through Savin Hill instead.
And let's not forget the highway politics here. The only reason transit is under such enormous pressure to contort itself into limitations here is because the lobbying is strong for a wasteful I-93 HOV lane expansion that eats as much transit space as it can bully for itself for an add-a-lane grab that does
not address 93's primary Dorchester deficiency at all: lack of breakdown lanes, and the associated lack of resiliency. The more work the transit side does twisting itself into a pretzel over cost-saving tensions vs. overly precious proof-of-concept overload, the less the asphalt lobby is forced to rationalize the crummy value proposition of the CURRENT zipper lane and its eating of all of the Expressway's breakdown resiliency...much less the insatiable appetite to keep adding more lane capacity. This is an explicit trap. The MPO's garbage study here that called for burying both Braintree AND Old Colony to total cost blowout should've been the reddest of all flags that cost control is seen as a one-way street that only transit is held to. So realize up-front that all that temptation to go scorched-earth compacting for high-concept's sake is taking the bait hook/line/sinker. With the number of bridge touches required to extend the HOV, the 93 side of the fence will spend several times over the cost of a Braintree-under-Ashmont capped box cut burial through Savin Hill with 2 at-grade OC tracks that nets all capacity gains at zero ops demerits.
Spend several times more on the highway side of the fence. Every scheme that tries to squeeze blood from RL ops to the minimum possible margins is doing so the highway can get a few freebies for its own blowouts. Why are we in such a rush to do this to ourselves at the expense of the highest-capacity mode first, next-highest capacity mode second...lowest-of-all capacity modes reaping the spoils?
Alright...if we're going to keep grinding at this high-concept obsession for compacting all that doesn't need to be compacted and which creates more problems than it solves, let's at least start doing that eyes-wide-open here for a change. MassHighway and the MPO
want us to get distracted and lost down a wormhole finding a way to zero out track space, because it's doing all the heavy-lifting for their HOV capacity grab. They're going to be at their concern-trolliest at "tunnel" cost and onus being all on transit to zero that out, when in reality this is not a subway at all but a Wellington-style capped cut and the highway bridge mods for extending the zipper lane into the Airport HOV's will exceed the cost of that cut several times over. The more mental energy transit advocates waste twisting themselves into a pretzel on this, the easier a job asphalt world has self-justifying HOV expansion that they know up-front will never amortize itself.
goo.gl
www.bostonglobe.com
