Disney Guy wrote:I heard a discussion on the radio (WRKO) today about the North South rail link and they mentioned not needing as many stub end tracks at North Station and South Station.
Let's imagine that the NSRL was up and running tomorrow.
The routes designated as north south through routes will no longer have fixed departure times out of North Station and/or South Station since those trains may not wait (as if at a timepoint) at either of those stations.
Today, without the NSRL, fewer stub tracks would be needed at North Station and South Station by eliminating fixed departure times for some trains. That is, the train would leave the terminal (North Station or South Station) as soon as passengers have disembarked/boarded or the train could change ends whichever came second. Some trains would deadhead to or arrive empty from layover locations elsewhere e.g. Beacon Park.
Hint hint: Could we eliminate some of the complaints of so many stops inside Route 128 by making some of them e.g. West Station or Yawkee the last inbound stops or first outbound stops, with South Station in between, on some trips?
The radio host also mentioned elevated transit. There are only three possibilities: underground, surface, and elevated. An aerial tramway (like a ski lift) would be interesting and probably not too bad looking. (The technology would probably not be a single loop moving cable and also the vehicles would be enclosed to avoid hazards below from falling objects.) But any elevated system would require transfers at both ends.
That's absolutely not the way it would work. Not even rapid transit operates on "come as they go" basis. Every single transit trip on every MBTA mode is backed by a printed schedule that has to be dispatched, and is subject to mitigation ("We will be standing by for a schedule adjustment") when the trains slip off that schedule. Just because the service is regular enough that passengers don't have to see that printed schedule and can plot trips on X-minute headways doesn't mean that every train isn't held to an individual schedule all the same. Dispatch wouldn't be able to do its job past a certain service density threshold if train positions vs. the clock were completely and utterly random. Not on the single-line Orange Line much less something as complex as the diverging routes of CR.
Every tunnel portal is going to have a high-traffic interlocking where it meets/crosses a surface route. And those will have to be run on a dispatcher schedule all the same or else those interlockings are going to become their own capacity-limiting chokepoints due to the random arrival times. It helps that Fitchburg, Fairmount, and the Old Colony are getting their own portals to spread this around to several interlockings matched to one mainline only; it helps to load-spread and simplify dispatching in some places. But you've still got two hugely critical new portal interlockings with LOTS of crossing traffic: 1) the NH Main/Eastern/Western portal just north of Tower A where tunnel traffic has to cross over surface traffic to reach the Eastern + Western, and surface traffic has to cross over tunnel traffic to reach the NH Main; 2) the NEC/Worcester portal at Washington St. just west of Cove where NEC Tracks 1, 2 and/or 7 need to be crossed over to get in or out of the tunnel.
Dispatch these two interlockings well and you'll hit the uppermost capacity limits of the system from mainline track capacity well before "Tower A+" and "Cove West" get their capacity infringed by trains tripping over each other. But throw slots through there at random from at-will turnbacks not adhering to a paper schedule and the interlockings themselves are going to have such constant conflicts that they impose a far lower ceiling on CR system capacity. There's no other way to do it. Not everything is a homogenous 10-15 minute Indigo headway where some Green Line-esque "We're standing by for a schedule adjustment" corrects the flow. You have 128-oriented/dense-stop/dense-headway Indigos mixing with 495-oriented/less dense-stop/less dense-headway suburban trains that will still see peak vs. off-peak shift change surges and throttle-backs. You will still have more marginal branchlines like Greenbush or Hyannis that'll never quite hit the demand uniformity to run clock-facing schedules and will always to some degree be "conventional" scheduled to avoid lighting money on fire for empty midday or late-night trains. You will still have Amtraks running on a paper schedule to D.C., and secondary Amtrak routes like the "Downeaster Regional" and "Concord Regional" running at somewhat lesser headways adjusted to population and demand. You will still have LD trains like the Lake Shore Limited and Boston-flank Montrealer running only a couple times a day. And you will have a priority pecking order on what most needs to use the tunnel vs. what most needs to stick to the surface, driven by demand between destination points and orientation on the compass. The system has to be able to handle all of this without interlocking conflicts inducing an artificial capacity cap. Euro and SE Asian systems have the same requirements for managing very very heterogeneous schedules calibrated to demand at whatever routes they run to. It's not cost-effective anywhere in the world to run a system that can't scale up or down to demand for the individual places it serves, and to the degree you
do see scheduling uniformity on a system it's more because the lines served by the system just happen to have more demand parity than the result of any sort of intentional ops strategy to give them all parity. The highest value proposition you can shoot for on capacity and flexibility is the ability to operate a system that can scale to
any headway and
any schedule at
any time of day on any
one service to maximize bang-for-buck, and do so while inducing a bare minimum of traffic conflicts.
That means dispatch operates on a paper schedule, whether that schedule needs to be shared with passengers or not re: clock-facing runs. Just like rapid transit around the world usually still has back-office set schedules. From dispatch's perspective the practice of plotting off fixed schedules was perfected 150 years ago, and save for systems that are more outliers than the norm (e.g. more isolated and/or unusually homogenous than the norm) every evolution in dispatching precision since the 19th century has still involved some sort of set schedule per train. There's no reason to reinvent the wheel or otherwise mess with what works when we get our highest value proposition out of the Link by running set schedules through those uber-critical series of interlockings. It can all be made transparent to the passenger just like on rapid transit, so why limit capacity and flexibility of services through the interlockings by introducing unnecessary randomness?
Caveat: I certainly wouldn't expect a WRKO host to understand this, or any expert guest they have to get that technical on the air when the whole point of the interview is to boil down the gist of it in terms Joe Blow in the Car can understand. It's a limited forum not suited to those kinds of nuts and bolts, so can't fault them too much for being misleading. I guarantee no traffic engineer worldwide would ever ever recommend junking the entire history of dispatching best practices for this build, which is a retrofit of a legacy system and not any sort of end-to-end cleanrooming. The official studies make no such assumptions either. And that's why they are steadfast in explicitly avoiding any notion of this being a SEPTA analogue where the surface terminals either go away or get slashed back. Highest value proposition requires balancing both to achieve max capacity and max flexibility. Otherwise we're going to be complaining about "Tower A+" and "Cove West" being the capacity-limiting banes of existence (with the underground interlockings throwing their own conflicts on the pile) just like surface Tower A and Cove are today. That's simply trading the same capacity cap to a different terminal alignment, not freeing us from that cap.
Avoid the temptation to dig up excuses to bust down or get rid of the surface terminals for OCD notions of conceptual integrity. That's not how this is going to work, and not the capacity trade-offs we'd ever rationally want to incur. Using
every bit of terminal capacity to the fullest, surface or tunnel, is what gets us the infinitely flexible system of our dreams. And the tippy-top capacity potential of the surface half of that system of dreams will be available to exploit from Day 1 of tunnel service, so why waste time fixing what won't be broke when the ribbon gets cut at the portal. No notion of conceptual integrity is worth the unnecessary loss of 100-year capacity and flexibility.
