Orange Line questions

Follow up to my South Bay alignment question.

I dug around (didn't find anything) but I did some first hand exploring (don't worry, all my visual gathering was done legally) and to the best of my knowledge, this is the area in the present day:



And these options are what I see as the best possible:

I like it. I think that you're right on target with making the storage track double-tracked. The tunnel was made for double tracks so why not make use of it. The only other addition to whatever switches and crossovers you would put in here, along with re-grading, would be that you would have to have a virtually fool-proof method of preventing two trains from coming together at the junction. It would even have to go beyond mere signalling as you are dealing with the "uncommon" event here with a train coming in or out of the "Essex Tunnel". Perhaps an electrical switch, de-activating one side while energizing the other ? Junctions are a nightmare, especially in a tunnel. Copley's has seen many a bang-up. I say it's worth it for otherwise is a perfectly good tunnel going to waste ! (another in a list)

Yellowspoon wrote:Two questions about the Orange line, in the vicinity of State Street station:

1> If one stands on the northbound Orange Line platform at Downtown Crossing and looks down the track towards State Street, one can see a signal light that contains yellow-over-red signal (or red-over-red just after a trains passes it). On the southbound side of the Haymarket station, at the south end of the station, there is a similar signal. On the northbound side of the Haymarket station, there is a red-over-red signal at the south end of the station facing north (not in the normal direction of travel). Is there a crossover between Haymarket and State? I've never seen one on any track map. If there is not a crossover, what are these signals for?

The signals are set up to turn a train in those stations for single track operation. They are basically holding signals to prevent you from continuing on.

madcrow wrote:The (State) NB and SB stations were originally separate stations. Additionally, back when the whole system was first built, access from East Boston to Roxbury/JP would have been a fairly unusual pattern. Access to/from EB didn't become important to the rest of the city until the age of air travel...

The walkway between the State northbound and southbound platforms, despite its length, was a no-brainer because the space it occupied (above the NB tunnel) was already excavated as part of the cut and cover construction.

As mentioned in another thread, no such space (at least in walkable dimensions) continued all the way to the northbound Downtown Crossing platform.

BostonUrbEx wrote:Does anyone know the approximate length of the South Cove tunnel in its present state? I was just imagining it as a little mini-layover/disabled train track. Even room for just 2 trains would be nifty, a southbound train could just be switch right out on it, or a northbound can just reverse and be shoved in. From what I recall from a Boston.com vid somewhere, the tunnel was in excellent condition, and I think the tracks may have even still been in place? I assume the tracks would need replacing though. But other than that, what do you have to do? Just knock out a wall and line up some switches?

That could also mean 2 more trains that could be ordered in the future. (maybe more, but I assume it's too short)

While I fail to see the practical need for such a siding, it's not even possible. Much of the area that was formerly part of the exit tunnel has been consumed by Tufts Medical Center.

From the intersection of Kneeland and Washington Streets, the current tunnel extends about 200 feet south of this intersection before turning west to the Tufts T station. From the turnoff, its only another 250 feet to Au Bon Pain at the main entrance to Tufts Medical Center. One flight down, directly under Au Bon Pain, is a hallway that extends over 400 feet almost to Oak Street. Unless I made some error, most of that hallway occupies what was once the Orange Line ramp to the portal at Nassau Street. Even if there is nothing between Au Bon Pain and the turnoff (and there probably is something there), that's not even enough room for a four car train.

Where is this in reference to the Don Bosco high school station,I think there was one there at one time.

Teamdriver wrote:Where is this in reference to the Don Bosco high school station,I think there was one there at one time.

Next stop inbound. That would have been Boylston/Essex Station, later re-named Essex. If you were heading outbound, you probably would have entered at the Lagrange St. entrance, closed in the 70's. Inbound, at Boylston/Wash. The station is still there, now called Chinatown.

Not sure if this was mentioned but why does the OL only function with a red over red or a yellow over red signal system and nothing else??

The orange and red lines are ATO (Automatic Train Operation), a form of cab signal system which actually controls the trains. The only wayside signals that still exist govern interlockings.

Yellow over Red: Switch Normal
Red over Yellow: Switch Reversed
Red over Red: Do Not Pass

MBTA1052 wrote:the OL which has a max. of 40 mph in the tunnels and 30 to 35 mph outside the tunnels

Why does the OL have a lower speed limit when outside of tunnels? This seems contrary to what one would expect...

I'm not sure why but sometime I board a OL train the cab certin is not fully closed and I can see the speedo move same for the Red Line on the Ashmont trains 01800 series when running between Savin Hill to Ashmont max is 39 and Braintree 49 could it be the distance between stations that causes the change in speed??

[reposting this in the correct topic]

This morning at about 8:45, I saw a 2-car Orange Line train headed inbound at Sullivan on the third track. What was up with that?

Probably a test train from Wellington. They use that track to get bugs out of equipment.

Alright, I've seen a lot of generalities about headway capabilities on the Orange Line. I'm looking for facts and details.

But first, I can't help but to preface the inquiry with a little commentary. If the Tournament of Roses Parade can have less than three minute intervals between floats, the Orange Line ain't run so fast that it can't do as well. Geesh, these are single file vehicles operating mostly under 35 mph. Our most timid and slowest octogenarians will operate cars at those speeds with far less than a football field between them, and Lord knows how fast some massively heavy big trucks travel with virtually no headway.

It would seem that without any technical assistance at all (automated signaling), that we could do FAR better than the approximately 5 minute headways. As posted elsewhere on this forum, I've seen evidence of much better service provided in the first quarter century of the transit system without all of our modern day computerization and mechanical advancements.

Thus, who here (if anyone) can explain with technical specificity, describing the step by step, cause and effect, rationale for the 4 minute headway limit of the Orange Line (4 minutes being the most recent official statement of the minimum)? And, please, I know the trains have to be available, ergo, imagine an infinite number of trains at our disposal.

And, if you offer 'blocking' as the end all reason, please go where no poster has gone before, to explain why one blocking is better than another and why is it, as some have suggested, cost prohibitive to change the blocking? What is involved?

I'm suspecting that at one point in the last 50 years, a management decision was made to totally remove the operational spacing of trains from human control and put it in the hands of electrical and mechanical gadgetry. Whether that decision was made for a well intended purpose or as a political reaction to a collision, or even less appealing, to create a dependency meant to enrich particular businesses, it became an entrenched philosophy which no one dared to override. And thus millions of riders annually are subjected to a needlessly sluggish, and sometimes crowded commute, because everyone fears their stature will be diminished if they admit that they can't see the Emperor's new clothes.

Thanks a bunch, in advance.

The OL can support tighter headways within the existing signal system with more cars. I don't know precisely how much because I don't know how the signal blocks are arranged, but Red Line is a good measuring stick and the OL currently runs much longer headways than Red. I don't see any reason why they couldn't pack them in the same, as it's a shorter single line that doesn't throw any traffic management curveballs like Columbia Jct. or Harvard curve and is generally arrow-straight on the portions rebuilt in the last 35 years. The 01200 replacement order is for 146 cars, a +26 increase from the 120 currently available. That's 4 more potential rush hour consists plus a spare set.

ATO is a mixed bag as a signal system. On the one hand it's safer and more reliable than trip arms, which are mechanical equipment that outdoors has to have heaters attached to work in bad weather. ATO is just a solid-state track circuit. For maintenance and reliability solid-state hardware is always better bet than mechanical. The only heavy-rail collisions the T has experienced in the agency's lifetime outside of yard limits have been operator error because trip stops can't enforce speed limits, only stop at a block. The downside is that ATO is still a pretty "dumb" system, being just a 1-bit one-way pulse signal. The operator still has to control the vehicle within the speed limit or get a stop penalty with everyone getting thrown from their seats when the brakes get suddenly applied. And staying within that small margin of error at the speed limit and reacting in the 5 seconds the operator has to slow down before getting the penalty means a herky-jerky ride and much wider train spacing because of all the unpredictable penalty stops. This isn't as much a problem on the longer-headway and car fleet-poorer OL as it is on the RL where those stops really start to add up and hose rush hour schedules. The T compounded the issue by not taking into account the traffic loads and platform dwell times downtown with tighter signal block spacing, instead opting for pretty much uniform blocks. That kills it from the Park St. approach to past Broadway when everything gets backed up due to long unloading/loading dwell times at the Park and DTX platforms. There's no leeway to catch up when it takes a minute longer than scheduled to close the doors because the platform is packed like there would be if they chopped into smaller blocks.


The future is Communication Based Train Control (CTBC) signaling, which is basically "smart" 2-way high-bandwidth ATO between computers controlling the signals and an onboard computer on the trains. Allows the trains to communicate back to traffic control instead of just getting that rigid 1-bit signal, and the track circuit pulses can convey much wider variety of information computer-to-computer than it can "dumb" system to "dumb" system. Allows the train to make much more fine-tuned speed adjustments, and the central control computers to make signaling decisions based on the whole line's traffic load because it can real-time track positions of every train on the line (i.e. no need for a GPS unit because the cab signals do it themselves). Operators still have to manually obey the speed limits or go into penalty braking, but it reduces their responsibility a bit more and isn't nearly as all-or-nothing as an ATO speed penalty. All of these are the reasons why this system can allow much tighter signal spacing...makes more nimble adjustments, doesn't have to over-space as ridiculously much for penalty buffers on the schedule.

This is already in use on I think 5 worldwide metro systems and is getting to be pretty mature technology. NYC is testing CTBC on the L train as a trial, and the T's got studies programmed for the Green Line and Blue Line. This is basically the system that would replace the Green Line's full manual block signals in the subway and on the grade-separated branches (surface branches still obeying traffic lights as before), as CTBC does have light rail applications with even tighter spacing in exchange for a little more operator leeway. Goal is to actually get something in place in some future when the T actually has money. For Blue they're just doing the research and haven't committed to building anything. What would force a decision there is if the Lynn extension got built, as it would almost double the above-ground route mileage. They'd be reluctant to double the number of trip arms and trip arm heaters and probably would bite on CTBC from Day 1. Retrofitting the rest of the line probably wouldn't touch the subway until some later date (OL operated for 20 years with half-ATO/half-wayside), but would allow them to decomission all those weather-beaten trip arms and heaters above-ground, likely with the switchover happening at Airport simultaneous with the 3rd rail/overhead switch. And then they'd tackle the subway later where the climate control doesn't wear out the trip arms as fast and the route miles are very small.

Some costs (in 2003 $$$) for upgrading: http://www.bostonmpo.org/bostonmpo/pmt-old/PMT-2.pdf. It's expensive mainly because it involves replacing 100% of the signal wiring with fiber, and no line currently has existing fiber signal wiring except for the spanking-new OL ATO Haymarket-Oak Grove and GL North Station-Lechmere (+ planned for the extension). Blue would cost $228 mil to retrofit, Orange would cost $367 mil, and Red a whopping $789 mil. Reason why they're only studying it for Blue, even though Red needs it extremely badly just to keep up with current traffic growth. CTBC would allow minimum 2-minute headways vs. 3-1/2 minutes on Red and Blue and 4-1/2 minutes on Orange, which also requires substantially expanding the vehicle fleets on each line to fill in those headways. You can see from that MPO doc what kind of ridership impact that has, though. +8000 to +11,000 new riders on each existing line with no extensions, and attracting anywhere from +2700 to +4500 brand new transit riders per line who aren't using any T service. Bigtime stuff. Subway signal replacement is...almost invisibly...one of the single biggest revenue boosters the T can undertake. In case you wanted another reason to hate how much time and money they're wasting pursuing frivolous outer-suburb commuter rail disaster projects. Every single one of these individual CTBC installs would convincingly outhaul South Coast Rail in new fare-paying riders.