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Discussion Starter · #1 · (Edited)
Does anybody happen to know for a fact what Metrorail's shortest theoretically-achievable headway with their current track/sensor/control system? I know it has something to do with block length (a block is an energized segment of track), and that the system was designed to surround each moving train with a buffer of at least one de-energized segment to make it just about impossible to have a head-on or rear-end collision -- by accident, sabotage, or otherwise. Apparently, the system was designed so that even a parked train on a non-powered segment will block the energization of an adjacent segment, so a speeding train would hit the unpowered segment and skid to a stop long before reaching the stopped train.

I'm pretty sure it's at least 4 minutes, and less than 7 minutes, but I can't find the exact number anywhere.

I'm interested, because one thing has been seriously bothering me about my proposed map... the possibility of a serious Metrorail "traffic jam" at Earlington Heights station that could make it impossible to run, for instance, a yellow, blue, orange, and green train in each direction every 10 minutes (6 per hour), because even if flawlessly synchronized that would put a train in Earlington Heights station every ~2:30 (less than a minute between trains if you assume it takes 2 minutes to slow down, stop, open the doors, wait 15-30 seconds, close the doors, and leave). I know that not even the Washington Metro could achieve anywhere close to that kind of real-world performance (apparently, their scheduling system starts to break down and cause logjams at ~4 minute headways, where a single passenger in a wheelchair causing a 20-second delay can set off a chain of delays that results in total gridlock and 4 trains backed up to enter a station an hour later).

The more I think about it, the more I become convinced that it might someday (with South Beach line added) become necessary to more or less "quadruple track" the section between Brownsville and Allapattah, and add a second island platform to Earlington Heights above the current one so that MIC-bound trains used the north side of the upper platform, Beach-bound trains used the south side of the upper platform, Brownsville-bound trains used the north side of the lower platform, and Dadeland-bound trains used the south side of the lower platform (with the whole scheme designed to make it easy to grab the first train going in the right general direction, exit at Earlington Heights if the train isn't quite right, then wait at one specific location where all trains going in the right SPECIFIC direction are guaranteed to pass. For example, someone heading to FIU from Dadeland could take the first northbound train, which might be orange or green. They'd exit at EH, take the escalator up, and could then take the next train (blue or yellow) to stop at the north side of the upper platform... being no better off time-wise if it's blue (since blue trains also come from Dadeland), but having beaten the clock and saved a few minutes if it's yellow).

reference map
 

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The more I think about it, the more I become convinced that it might someday (with South Beach line added) become necessary to more or less "quadruple track" the section between Brownsville and Allapattah, and add a second island platform to Earlington Heights above the current one...
Why even add a second platform? Do like they do in NYC Subway where there are 2 inner tracks that just run through the station. And the 2 outside tracks stop at the station platform. Of course down here the express tracks would probably have to run directly above the station. But it's not like Earlington Heights NEEDS to be an interchange station or anything. You could just send the Orange line down the same direction as the yellow instead of Dadeland. I bet very few people on the green line from those northern stations are even wanting to go to the beach now (from residential to residential), but if they need to anyway they just change lines at MLK or Brownsville. And the rest (coming from MIC) change at MIC to get to the Beach via yellow. Problem solved. Besides, do you really need 3 different lines going to Dadeland South and only 1 to the busy Miami Beach line?


If people will most likely end up switching anyways, why have the blue line? It doesn't go anywhere that can't be accessed by the green or yellow line.
I think his blue line is an express line. In which case I would suggest he needs to add Civic Center, Dadeland South, Dadeland North to the list of stations that the blue stops at. And maybe even Overtown now that its finally getting popular with that new building they just built right up against it. I would also suggest making the red and purple lines dotted lines to show that they are not Metrorail modes of transportation, but other light rail.
 

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I believe that the French have achieved 30 trains per hour on sections of the RER network and the British are proposing 24 trains per hour for the upgraded Thameslink services. I both cases the signalling has been designed for these intensive services and the trains run at relatively low speeds as the station dwell time is the critical factor.
 

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Discussion Starter · #5 · (Edited)
Blue isn't 'express' (it stops at all the stations), but exists because I believe the overwhelming majority of people who board a train between downtown and Dadeland, then pass through Earlington Heights station will, in fact, be heading to MIC or somewhere west of it (ditto, for the reverse). In computer engineering, it's called a "use case" -- a scenario that applies to the majority of users, so you make it the effortless default.

That's the same reason for the upper platform at EH: to ensure that someone who's heading to an area served by two or more lines and really doesn't care which one arrives first can stand in one specific place and know that all trains heading to that area will pass by that platform. IE, someone heading towards MIC from EH doesn't care whether the next MIC-bound train is blue or yellow, because either will do. If blue were on one platform, and yellow on another, he'd likely end up frustrated or out of breath 50% of the time due to being on the wrong platform. The reason for having upper and lower platforms, instead of two at the same level connected by a mezzanine, is because that doubles the vertical distance... to get from one to the other, you'd have to go up, across, then back down again. Vertical travel sucks, but twice as much vertical travel sucks four times as badly ;-)

Actually, the upper/lower scheme works well in another way. By putting MIC-bound trains at the upper platform, they can proceed straight out of the station, then turn left/south and go over the northbound tracks. If MIC-bound trains were at the current platform level, they'd have to do a fast, steep climb to get high enough to clear the northbound tracks before the northbound tracks themselves turned north to 27th Avenue. Ditto, for putting Beach-bound trains on the upper platform... if they were on the lower platform, they'd have to go up at a fairly steep angle to clear the southbound tracks before they turned south to 17th Avenue.

The downside, of course, is some very expensive vertically doubled trackwork in the mile along SR-112 between 17th and 27th Avenues. Essentially, the yellow line from South Beach runs through the existing 112 corridor, but has brand new tracks of its own, plus the rail equivalent of four braided ramps:

* one to allow MIC-bound blue trains to break away from the northbound mainline immediately after making the turn from 17th ave to 112, rise up to the level of, and merge with, the MIC-bound "yellow" track before entering EH station.

* one to allow future potential Dolphin Stadium-bound trains from South Beach to break away, go down to the level of the original mainline, and merge into the northbound track before entering EH station.

* one to allow Dadeland-bound trains coming from MIC to break away and merge into the original southbound mainline immediately after it makes the turn to 112 from 27th ave.

* one to allow future potential beach-bound trains coming from Dolphin Stadium to break away before the curve from 27th to 112 and rise up to merge with the beach-bound track coming from MIC before entering EH station.

Remember, the point is to allow trains coming from all four directions (Dadeland, South Beach, northline, and MIC) to run at full speed and arrive at exactly the right time to merge into their slot with computer-choreographed Japanese precision (in Japan, station guards will actually shove people in or out of a train if they think that person is moving too slowly and might delay it beyond its allocated 15 second dwell time). At its busiest (10 minute headways for each color), there would be a train arriving at one of Earlington Heights's two platforms every minute and fifteen seconds, a train arriving at alternating sides of each level every 2:30, and a train heading to one of the four endpoints accessible from Earlington Heights (Dadeland, Beach, North, MIC/FIU/Metrozoo) every 5 minutes.

In theory, it might be possible to achieve the same volume without the level separations IF the trains were run like cars with impatient drivers on I-95 at 3am... but in the real world, they'd never be allowed to run them like that (tailgating at high speeds, and ramming trains through frogs and wyes at the absolute limits of their design speed). If the control system requires that all Metrorail trains be separated by at least one full 8-car train length (or more!) at all times, and the trains aren't going to be braked and accelerated in and out of stations as fast and hard as they can, then I'm convinced that two levels will ultimately be necessary to achieve acceptable peak headways.

That said, as long as the north half is fairly useless and doesn't have many riders, it'll probably be OK to just run green and orange with one train every 20 minutes, and blue and yellow with one train every 10 minutes (alternating a green and orange train between every departing blue train from Dadeland, and timing blue departures from FIU to arrive at Earlington Heights exactly halfway between the last green and the next orange (or last orange and next green).

Incidentally, I think this is similar to what they've talked about doing (at unholy cost, since it's all underground) in Washington DC between Rosslyn and Stadium-Armory -- splitting blue and orange into their own tunnels, and rebuilding the stations to put eastbound blue & orange on opposite sides of one level, and westbound blue & orange on opposite sides of another. The main controversy (aside from the insane amount of money it's going to cost) being whether they might as well just reroute blue or orange to new stations a few blocks away (possibly including one or two in Georgetown) since it would probably cost less than trying to mine out entire new station levels below the existing ones (the stations were built as cut & cover, but most of the stations now have buildings sitting above them). In a very real sense, it would be kind of like trying to build a waterproof, finished dry basement below an existing house on a slab in Miami without damaging the house or disturbing the people who live in it. Except it would actually be even harder than that.

 

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Canes, that map of the DC Metro really makes me miss that system. It's actually the only thing I miss about Washington. Philly is far cheaper and packs more punch as a real city, but the Metro kicks ass.

Wasn't aware of the proposed Blue Line reconfiguration. I believe there was also talk of an extension all the way out to Dulles (a LONG way for those unfamilair with D.C.) as well as an insanely long Metro "circle" line that would roughly parallel the Beltway.

With the crazy funding largesse they benefit from, though, I guess anything is possible---especially with the system enjoying such huge ridership numbers.

But anyway, enough rail envy. Back to Metrorail.

The maps and theoreticals you've posted here are some of the best stuff I've ever seen on this site. It's extraordinarily good work and I only wish people like YOU were the ones doing transit planning in this country.

But when we talk about Metrorail we've got to keep one eye one reality---on what is actually possible rather than what we all (myself included) would like to see.

Honestly, I think a realistic Metrorail plan at this point is to make sure they don't screw up the MIC...hope the North extension gets built...and start rethinking everything after that in terms of light-rail. The money for the other stuff (subways to Miami Beach, etc.) just is NOT there and isn't anywhere on the horizon, either.

We have to be realists about this. The feds (to their discredit) are only going to fund a tiny percentage of what is asked for every year from various transit agencies in various cities and Miami's needs are only graded as marginal from their perspective, unfortunately. They aren't about to fund tens of billions of dollars for massive heavy-rail expansion in Dade County.

Why? Well, for starters Miami (and the Miami MSA as a whole) aren't growing as fast in population as many of us think it is, at least relative to other cities with equally pressing transit needs.

For example, the U.S. Census Bureau shows the following estimates from 2000-2006:

Miami MSA (Dade, Broward, Palm Beach): 5.5 million population; 9.1% increase. Approximately 456,000 new residents.

Atlanta MSA: 5.1 million; 21.1% increase.

Houston MSA: 5.5 million; 17.5% increase.

Dallas MSA: 6.1 million; 16% increase

Tampa MSA: 2.7 million; 12.6% increase

Riverside/San Bernardino MSA: 4 million; 23.7% increase

Phoenix MSA: 4 million; 24.2% increase.

Las Vegas MSA 1.8 million; 29.2% increase.

Washington, D.C. MSA: 5.3 million; 10.3% increase

What do those numbers mean? Those are the kind of places that Miami is in DIRECT competition with for transit funding and some of them are growing at twice or triple the rate. Houston and Atlanta will soon be larger MSA's...Phoenix will be next...probably a few others at current growth rates.

In addition, even already huge MSA's like Los Angeles and New York added more sheer people to their MSA totals than Miami over that period (NY 495,000; LA 584,000) despite obviously having a smaller percentage gain because of the huge existing population.

In FURTHER addition, relatively small MSA's such as Orlando (2 million) and Raleigh (1 million) grew at between 20-25% in the same period and will be next in line for funding. Not to mention a half-dozen other cities with similar numbers.

The Miami MSA is basically a narrow line that hugs the coast from Florida City to the Martin County Line. Well over 120 miles of linear real-estate. Even a dramatically expanded Metrorail could only serve a small fraction of that linear geography.

Based on the real numbers...based on geography...based on actual need...based on ridership and what's happening elsewhere and on the REALISTIC prospects of the federal government funding much more heavy-rail in Miami...I think it's time to change the thinking.

There aren't going to be subways going to Miami Beach. There aren't going to be Metrorail extensions to Aventura or Homestead, either, nor will visitors to the city be asking how to transfer from the "Blue Line" to the "Orange Line" amid 25,000 frantic commuters in an underground extravaganza. You wanna see that? Go to New York.

What CAN happen is a far better transit system than currently exists.

Miami needs to become a LEADER in fighting for light-rail, rather than a johnny-come-lately. THAT'S where the federal money is now.

Anybody up to writing that letter to your Congressman? :cheers:
 

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Discussion Starter · #7 ·
Well, I did a little more reading about the DC proposal last night. It looks like the whole thing was shelved for now, and they're studying the feasibility of trying to accelerate and decelerate the blue/orange trains faster & harder (the problem isn't the trains, it's the passengers who'll quite possibly end up on the train's floor if it tries to do 5-50mph in 10 seconds pulling out of a station, or roar into a station at 30mph and come to a dead stop by the time the last car fully emerges from the tunnel into the station. The problem was that mining out second station platforms underground was just going to be too outrageously expensive, full stop, and shifting the blue line would have probably left 30-50% of its riders transferring to -- and saturating -- Orange anyway. Another possibility they're apparently considering is to bore a parallel set of tunnels that would serve new blue-orange platforms ONLY at Rosslyn, Metro Center, L'Enfant Plaza, and Stadium/Armory. With a twist: passengers would NOT be allowed to transfer from "Express" blue/orange to "Local" blue/orange (though they WOULD be allowed to transfer to/from red, yellow, or green). How they'd actually enforce that is anybody's guess. The rationale is that the transfer stations are already saturated to the breaking point, and adding more people who only change trains there would break them completely, so they'd have to find a way to limit transfers to blue/orange express to ONLY those passengers who'd have to transfer to/from blue/orange anyway.

The DC example is interesting in another way... it's a system that exceeds its carrying capacity for much of the day, running as close to 100% utilization as you can possibly get, yet STILL somehow manages to lose money, and apparently has a new budget crisis every year. Utterly bizarre.

I semi-agree about the light rail, but I think the solution is for MDTA to aggressively find someone who can build vehicles capable of running from both 750v side-rail AND onboard diesel generator (with signals in the track to tell the train, "You're about to lose the power rail... start the generator NOW"). Then, they wouldn't have to decide whether any given line will be "light" or "heavy". It could be both, as merited by the surrounding area.

For a good example, consider a line that runs along the FEC corridor from the Port of Miami to Aventura. It could run mostly at grade, but freely go up and over (or down and under) major roads at will. It could go up and over the truly major roads (Biscayne Boulevard, 36th Street to Tuttle Street, maybe 54th and/or 62nd, 79th to 82nd, and definitely 163 & Miami Gardens Drive, but cross the minor roads at grade. It would allow them to break the rigid false dichotomy between 100% grade separation and 100% screwing up major roads. Disrupting traffic on Kendall Drive, US-1, 107th Avenue, or 163 Street would be a very, very bad thing. Disrupting traffic on NW 4th Street where CSX and FEC cross it now, or most other 2-lane and residential streets, is no big deal. They need to put away the meat cleaver "one-size-fits-all" plans and find a way to be more flexible.
 
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