MUNI Metro Subway - Unrealized Capacity

You may have read about MUNI's radical attempts to deal with congestion issues in its Metro Subway that runs under Market Street and also included the Twin Peaks Tunnel.  Long story short, MUNI is eliminating one seat rides downtown for riders on the J, K and L streetcar lines.  The given reason is since the J and K lines are limited to single unit LRV operation, those "slots" in the Metro Subway are being underutilized and the new operating plan will replace the one LRV trains with two LRV trains. 

The Metro Subway is signaled by a loop antenna based CBTC system in the style of LZB and if you are noticing a pattern between articles addressing CBTC and capacity problems then I thank you for being a long time reader.  Basically MUNI is noticing the capacity problems that stopped both SEPTA and MBTA from realizing a full CBTC fantasy in their respective trolley subways and MUNI's response is to make many commutes much worse.  To be honest this isn't just a CBTC problem as coded track circuits would have been no better and possibly worse.  The issue is a fear of less automated operation.

Here is an LRV on the eastbound track at the Embarcadaro terminal station, which seems to be the major capacity constraint as M, L, K and J line trains all turn back here.  You might notice a line of cones and a lot of unused platform space.  That is because at every Metro Subway station, only one train can platform at a time, even though the platforms are long enough to support two trains.

Here is the westbound track with a fresh train sitting behind the cones just hanging out with a second train close behind while they wait for the single loading/unloading berth to become available. On all of the Metro subway stations it is common for following trains to stop short on the platform and wait for the single loading zone to become available.  It is also common for passengers to run their buts off along the platforms to reach said single loading zone from the far end.

Both SEPTA and the MBTA use multiple berths at underground trolley stops to varying degrees.  For example at Juniper St there is an unloading spot and a loading spot.  At other stations different routes can stop at different points along the platform.  On both systems the signaling system is equipped with R/Y station signals that allow operators to creep forward and occupy the station behind another LRV.  It's not a cure all, but it helps. 

MUNI plans to update its CBTC system to one that uses wireless instead of loop antennas.  It might work better, it might not, but with new LRV's already arriving, maybe someone should have thought outside the box and ordered a radar based collision avoidance system to allow closer spacing in stations and thus pipeline the passenger boarding operation.  Once headways drop below two minutes, dwell time and terminal capacity dominate block separation.  It's why expensive CBTC systems don't move the capacity needle much and often do worse than traditional systems with on-sight operation, spring switches and loops.

PHOTOS: GWYNN Tower

The PRR's GWYNN tower, originally named GWYNNS RUN, was built in 1931-32 and replaced the small, wood frame VN (CalVertoN Yard) tower on the same location adjacent to the viaduct over Gwynn's Falls.  GWYNN served the function of a main line crossover, but being located only 1.5 miles from the end of 4-track territory at FULTON interlocking, its primary reason for existence was to support various industrial tracks south of the City of Baltimore in a similar fashion to MILLHAM interlocking north of Trenton.  With the collapse of urban industry in the Northeast along with a specific reduction of freight services along the Northeast Corridor in the Amtrak era, GWYNN and its entire interlocking plant were ultimately found to be redundant and subsequently removed and abandoned.

GWYNNs layout consisted of a 4-track complete crossover with connections to industrial leads at three of the four corners.  The original main track layout was 2+2 single direction Rule 251 in both directions, although by the Penn Central era track 3 had been converted to Rule 261.  By the 1940's both logical pairs of crossovers were equipped with Limited Speed #20 turnouts with signals having the appropriate yellow triangles. The intent was to allow both passenger and through freight to bypass local industrial movements tying up the outer tracks directly south of the city The tower also had remote control of two nearby interlockings to the south, LOUDON PARK and WINANS.

The demise of GWYNN came with the Northeast Corridor Improvement Program (NECIP) of the early 1980's.  With the aim to increase speeds to 125mph and remove costs associated with legacy freight infrastructure, Amtrak rationalized GWYNN by replacing the old interlocking with the MP 99.3/4 automatic signal location and, in 1985, transferring some of the functionality to a new interlocking named BRIDGE, 1.1 miles to the north (although it can be argued that BRIDGE is more a devolved FULTON than a relocated GWYNN).  Note in the 1992 Amtrak diagram below that the #5 track, #0 track and Gwynn industrial track have all been removed as of 2020.

The former northbound signal bridge now serves as automatic signal location 993 for southbound trains and 994 for northbound trains.  The NECIP completely eliminated Rule 251 operation south of Philadelphia and at this point all 4 tracks were bidirectional.  Note that the track to the far right is track #3 and the track to the far left is track #A, which is different from the PRR which numbered them 1 to 4.

Here we see GWYNN tower and the straight railed interlocking plant looking first northbound then southbound, which compares rather poorly to this 1977 view.

 

The southbound signal gantry today sits empty north of the Gwynn's Falls viaduct, but is past function is still obvious.

Similar in design to towers like CORK, GWYNN was a throwback to the more ornate towers of the teens and twenties, just before the general adoption of  the cleaner designs of the 1930's.  Compare the wooden bay window to that of WINSLOW tower, built just a few years later.  In the photo below, taken around 2005,  we can see that whole the structure is clearly decaying, it is relatively graffiti free and appears to have had a spot of paint applied to its concrete foundation. 

15 years later the tower has seen some significant deterioration with the wooden bay window structure having completely rotted off and the walls not covered in spray paint.  Unlike the DL&W style towers which had poured concrete roofs, the PRR tended to use wooden roofs and once the roof is compromised it tends to undermine the rest of the structure.  Fortunately the cantilevered bay window floor did not appear to be going anywhere. 

Exit Stage Right - Leaving Signaled Territory

Typically I write about railroad signaling, occasionally touching on non-signaled block systems such as TWC or DTC.  Each are more or less straightforward on their own, but things can get interesting when transitioning from one to another, specifically from signaled territory to non-signaled territory.   the three primary methods are:

1. Exiting at a Manual Block signal
2. Exiting over Restricting
3. Exiting at a sign

Although some of these have a few additional complexities that I will go into below.

WINSLOW Jct on the PRSL had two exits into Manual Block territory.

 Under mostly defunct manual block systems, trains would be admitted to the block by a manual block signal, typically under a modified Clear indication like Rule 280 Clear Block in the PRR Rule book.  These signals would be located at the start of manual block territory directly after the interlocking or on the last signal on a route that could lead to manual block territory.  A signal less favorable than Clear Block would be preceded by an Approach-type indication.

NORAC Rule 290 Restricting into DCS territory.

With the coming of Track Warrant systems like Conrain's Form D Control system (DCS), trains moving from signaled territory to DCS territory would be given a Restricting indication, regardless of the trains DCS movement authority.  In fact this method of operation was written into the text of NORAC Rule 290.

Proceed at Restricted Speed until the entire train has cleared all interlocking and spring switches (if signal is an interlocking or CP Signal) and the leading wheels have:

1. Passed a more favorable fixed signal, or
2. Entered non-signalled DCS territory

 This is also the standard when trains are moving into a yard or non-signaled sidings, although in those situations the train is entering Restricted speed track as opposed to a non-signaled block system.

Seaboard Rule 290 Restricting into Collier Yard.

In addition to placing the Restricting signal at the entrance of the interlocking, it can be placed on an exit signal allowing higher speeds throughout interlocking limits.

Exiting at a sign means that signaled territory ends at a sign instead of a signal.  This can be used with signaled approach blocks to allow reverse direction trains to occupy the approach block without needing to get a track warrant, as seen below on the old D&H near Saratoga Springs, NY.

 

Where signaled approach blocks are not present, the exit sign can be used at the end of interlocking limits.  As with the Restricting exit signal, this allows a more favorable indication, such as Approach or Slow Approach, to be displayed at the start of the interlocking.  This in turn allows higher speeds for pretty much the cost of a sign and also better supports non-restricted speed track as, unlike the Restricting signal, Restricted speed is not necessarily required if the train possesses non-signaled movement authority.

NJT ARCH interlocking eastbound home signal.

Recently a more radical take on the exit sign has started cropping up.  Instead of treating the signal as a virtual restricting signal demanding an Approach-class signal in advance, some railroads, including Norfolk Southern, have been configuring their interlockings to display Clear-class signals into an end of signaling sign, even if that sign is located at the interlocking limits.

For example, at CP-PORTER, shown above, the main track signal displays Approach for a straight route towards Restricted speed track marked by a sign at CP-PLANT.  However it also can display Slow Clear for the diverging route directly into a Track Warrant territory (Rule 171) sign at CP-PORTER's southern limit.   The only other option is Restricting if the route is occupied within the interlocking itself.

Trains being signaled into Yard Limits directly north of CP-PORTER get an Approach-class signal on the straight route, but a Slow Clear on the northeast wye track.  While all this inconsistency can technically be considered safe as the signs technically overrule the preceding Clear-class signal.  Still, I am not a fan of this practice as it is important to never violate the contract that a Clear-class signal provides two clear blocks ahead and an Approach-class one clear block.  Unless approach blocks are being used, a signaling system has no idea about the state of the track in unsignaled territory and a Clear-class signal would be writing a check the signaling system cannot guarantee.

Japan Shows Us How It's Done (again)

I found an interesting puff piece on Youtube showing off Keikyu Railway's method of supervised train dispatch on their 87km network on the Miura Peninsula south of Tokyo.  Similar in feel to Chicago's CTA or the NYC Subway, the dispatch system shuns centralization and computerized control for the sake of service quality and fault tolerance. 



The line is divided into 20kn sections, each with a master tower located at a segments' most important station.  The interface is a second generation unit lever panel (not N-X) and the well trained operators are able to achieve an astonishing level of throughput that includes dynamic trainset management.  Through operational skill and a signaling system that doesn't get in the way, train movements are scheduled down to the second.  The video also describes how the human-focused system has a high degree of fault tolerance because each master tower has the surge capacity to adapt to all types of failure that would tend to overload a remote dispatcher or dispatch office.  Still, a remote chief dispatcher is available to assist and coordinate if the need should arise.  The result is Keikyu having the one of the highest on time performances in Japan.

Of course in North America we don't care.  Traffic levels are low and delays are typically seen as a cost of choosing transit. Our levels of training and operator competency require technical guard rails like PTC and fixed trainsets that further reduce efficiency.