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Old 04-16-2015, 07:19 AM
 
Location: Kirkwood
22,167 posts, read 16,168,399 times
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Quote:
Originally Posted by arjay57 View Post
Why not cut all the trains to 2 or 3 cars and shorten decrease headways even more. Trains are rarely full except during peak hours.
Negative, MARTA has a higher average occupancy rate than many larger subway systems. The research I saw from 2 yearsvago showed over 70% of capacity is used on average trains.
Also, reducing the cars for off peak how would the cars get added back for peak hours again? Thstbeould require taking the trains out of revenue service and coupling thebcars and testing systems.
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Old 04-16-2015, 07:21 AM
 
985 posts, read 1,430,731 times
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Quote:
Originally Posted by arjay57 View Post
Why not cut all the trains to 2 or 3 cars and shorten decrease headways even more. Trains are rarely full except during peak hours.
They did this last summer and it caused a slew of headaches. They received enough complaints about overcrowding to revert back to 6 cars. This only works if headways are 7 minutes on red/gold lines. I'm all for it, but I don't think the ridership is there yet.
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Old 04-16-2015, 07:19 PM
 
Location: Decatur, GA
4,908 posts, read 3,709,955 times
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Quote:
Originally Posted by cqholt View Post
All lines other than green line run 6 car trains. By reducing trains to 6 cars, MARTA was able in increase frequency without adding a lot of additional cars. 15 minute headways: 4 trains per hour with 8 cars= 32 cars. 10 minute headways: 6 trains per hour with 6 cars= 36.
Wrong, they didn't "reduce" the number of cars when they went to 10/12 minute headways. Well, they did try 4-car trains on the Red and Gold lines, but it was a disaster and they quickly ran 6-car trains again. But just because 6 cars is the norm, doesn't mean that always will be. For one, the entire rest of the system is 8-car platforms and it's doubtful MARTA would deliberately design yet another system restriction. For two, designing for 600' platforms when the existing one is 150' doesn't require all that much extra work over just going to 450'. For three, the Stonecrest line could become the busiest line until the Red line is extended to Windward Parkway and could well need 8 cars, the Blue line is basically standing room only by the time it reaches King Memorial every day. For four, they do run 8-car trains occasionally during special events, when I attended an ARC event in Decatur, they were setting up 8-car trains at Indian Creek.
Quote:
Also, MARTA has to make sure it has enough cars in reserve just in case and they are always doing maintenance on others.
MARTA is ordering a new fleet within the next two years so they will have plenty of "reserve" cars assuming they aren't stupid and try and nickel-and-dime themselves into a bad situation. As much as I have knocked Keith Parker's operation of the system, he's no slouch when it comes to planning so I expect them to get this right.
Quote:
Originally Posted by arjay57 View Post
Why not cut all the trains to 2 or 3 cars and shorten decrease headways even more. Trains are rarely full except during peak hours.
The trains are very full off-peak. To maintain the same capacity per hour as currently (6 cars times 5 trains per hour is 30 cars per hour, times two lines is 60 cars per hour) running two-car trains would require headways of 2 minutes (30 trains per hour) on the shared portions. That's simply not doable for MARTA. Even the Washington Metro with its more advanced scheduling system doesn't manage to do better than headways of about 2.5 minutes so I doubt MARTA can reliably do better than the 4 minute headways they had at one time. To do 8-minute headways (4-minutes shared portions) you could use 4-car trains, but you'd have to run that headway all day long just to match the current off-peak capacity.

Increasing the number of trains also raises costs as now with 15 trains per hour per line, you need three times the number of operators and personnel costs are one of the higher operational costs in a transit system.

As for 3-car trains, MARTA's vehicles can only operate in even sets as two cars form "married pairs" that are essentially permanently coupled together.
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Old 04-17-2015, 05:52 AM
 
Location: Kirkwood
22,167 posts, read 16,168,399 times
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Quote:
Originally Posted by MattCW View Post
Wrong, they didn't "reduce" the number of cars when they went to 10/12 minute headways. Well, they did try 4-car trains on the Red and Gold lines, but it was a disaster and they quickly ran 6-car trains again. But just because 6 cars is the norm, doesn't mean that always will be. For one, the entire rest of the system is 8-car platforms and it's doubtful MARTA would deliberately design yet another system restriction. For two, designing for 600' platforms when the existing one is 150' doesn't require all that much extra work over just going to 450'. For three, the Stonecrest line could become the busiest line until the Red line is extended to Windward Parkway and could well need 8 cars, the Blue line is basically standing room only by the time it reaches King Memorial every day. For four, they do run 8-car trains occasionally during special events, when I attended an ARC event in Decatur, they were setting up 8-car trains at Indian Creek.
MARTA is ordering a new fleet within the next two years so they will have plenty of "reserve" cars assuming they aren't stupid and try and nickel-and-dime themselves into a bad situation. As much as I have knocked Keith Parker's operation of the system, he's no slouch when it comes to planning so I expect them to get this right.

The trains are very full off-peak. To maintain the same capacity per hour as currently (6 cars times 5 trains per hour is 30 cars per hour, times two lines is 60 cars per hour) running two-car trains would require headways of 2 minutes (30 trains per hour) on the shared portions. That's simply not doable for MARTA. Even the Washington Metro with its more advanced scheduling system doesn't manage to do better than headways of about 2.5 minutes so I doubt MARTA can reliably do better than the 4 minute headways they had at one time. To do 8-minute headways (4-minutes shared portions) you could use 4-car trains, but you'd have to run that headway all day long just to match the current off-peak capacity.

Increasing the number of trains also raises costs as now with 15 trains per hour per line, you need three times the number of operators and personnel costs are one of the higher operational costs in a transit system.

As for 3-car trains, MARTA's vehicles can only operate in even sets as two cars form "married pairs" that are essentially permanently coupled together.
WMATA just started ATC on the Red Line this year after the 2009 crash. All other lines use manual operation. MARTA, on the other hand, uses ATC on all lines. MARTA maintained it's ATC system and avoided the safety issues that have plagued WMATA.
I would like to see MARTA get driverless trains, when they purchase new railcars.
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Old 04-17-2015, 06:10 AM
 
Location: NW Atlanta
4,994 posts, read 3,480,819 times
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Quote:
Originally Posted by MattCW View Post

As for 3-car trains, MARTA's vehicles can only operate in even sets as two cars form "married pairs" that are essentially permanently coupled together.
Well, technically (if they really wanted to) they could bring back those single-unit Franco-Belge cars that they mothballed at Avondale years ago. Though I think those got converted into married-pairs as well.
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Old 04-17-2015, 09:19 PM
 
Location: Decatur, GA
4,908 posts, read 3,709,955 times
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Quote:
Originally Posted by cqholt View Post
WMATA just started ATC on the Red Line this year after the 2009 crash. All other lines use manual operation. MARTA, on the other hand, uses ATC on all lines. MARTA maintained it's ATC system and avoided the safety issues that have plagued WMATA.
What they took offline was the automatic train operation system, the ATC however remained online since that's the part that provides the safety-critical train separation. What WMATA has that MARTA doesn't seem to is an Automatic Train Supervision system that can reduce a train's speed in order to keep trains from bunching and reduce delays by slowing a train instead of having it stop. MARTA seems to use straight block-signaling with 5 speed codes transmitted to the train, 25, 37, 50, 60 and 70mph with no code being stop. MARTA does have track bailses like WMATA, but I get the impression from observation that they are primarily for transmitting track segment speed while the rails carry the signal speeds from which the train's computer will take the maximum of the two as the maximum safe operating speed.

Eventually, if these ridership gains keep up and we do end up having to operate trains on very tight headways, MARTA will need either a better ATS (if they do not already have one) or go straight to CBTC like NYC is implementing on its L train and then the 7 train. The advantage is each train gets its own "safe zone" around it rather than relying on fixed-length blocks which drastically improves throughput.
Quote:
I would like to see MARTA get driverless trains, when they purchase new railcars.
Technically they already do, all the operator has to do is operate the doors and punch the proceed button. Full automated train operation doors and all would likely require platform edge doors which would be a huge capital cost to retrofit the entire system. I do however hope MARTA considers automatic door opening for its next generation of train cars as sometimes it seems to take the operator forever to open the doors, particularly if they have to open both sides (Five Points, Lindbergh), this would speed station dwell which is especially important given the ridership gains this topic is talking about.

But what's interesting is the operators can drive the train better than the computers in the current vehicles. The computers apply maximum power until they "speed fault" (overspeed) then the brakes apply quite strongly and bring the speed down by as much as 9-10mph. A good operator can regulate power by watching the speed and if they do speed fault, suppress the alert by applying the minimum necessary braking, then reapplying power or coasting. This is particularly noticeable on the slow-zone through Decatur where the train "surges" through the 25mph zone when operating automatically since power and braking has a much larger effect at that low a speed.
Quote:
Originally Posted by Gulch View Post
Well, technically (if they really wanted to) they could bring back those single-unit Franco-Belge cars that they mothballed at Avondale years ago. Though I think those got converted into married-pairs as well.
MARTA had singles at one point? Were they cabless or were they true single railcars? Frankly, I wouldn't mind MARTA going with something like an A-B-B-A trainset in the future where the A-B cars are married pairs with the As having cabs and the Bs not to increase seating capacity slightly. It would make things more difficult at Avondale admittedly since there's no way to turn them around if they're facing the wrong way, South Yard and Armour both have WYE tracks. If Bankhead is still limited, that would not be good for flexibility unless the Green Line was restricted to the CQ-312s (presuming the 310s and 311s will be retired)
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Old 04-17-2015, 09:38 PM
 
Location: NW Atlanta
4,994 posts, read 3,480,819 times
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Quote:
Originally Posted by MattCW View Post

MARTA had singles at one point? Were they cabless or were they true single railcars? Frankly, I wouldn't mind MARTA going with something like an A-B-B-A trainset in the future where the A-B cars are married pairs with the As having cabs and the Bs not to increase seating capacity slightly. It would make things more difficult at Avondale admittedly since there's no way to turn them around if they're facing the wrong way, South Yard and Armour both have WYE tracks. If Bankhead is still limited, that would not be good for flexibility unless the Green Line was restricted to the CQ-312s (presuming the 310s and 311s will be retired)
20 of the CQ310s (Car numbers 501-520) were originally delivered as singles from Franco-Belge, and were later converted to married pairs (I think sometime in the 90s?). Presumably this was done for the purpose of additional operational flexibility.

Below is # 517 at Avondale Yard in 1981:



Basically, the only difference that these cars had from the other CQ310s was that the singles had cabs on both ends of the car, and that configuration existed after the conversion to pairs with MARTA simply removing the control panel from the non-operational end. It's been a while since I've seen one in service, and I don't believe that these cars went through the rebuilding process at Alstom a few years back.
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Old 04-17-2015, 09:58 PM
 
Location: Decatur, GA
4,908 posts, read 3,709,955 times
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Wow, interesting! Do you know if they ever ran them in revenue service as singles or were they always in a train?
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Old 04-18-2015, 07:38 AM
 
Location: NW Atlanta
4,994 posts, read 3,480,819 times
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Quote:
Originally Posted by MattCW View Post
Wow, interesting! Do you know if they ever ran them in revenue service as singles or were they always in a train?
I think they were always part of a train (I've seen photos of a 3-car configuration). By the time I started riding MARTA frequently in the early 2000s they had already been converted to pairs.
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Old 04-18-2015, 07:41 AM
 
Location: In your feelings
2,199 posts, read 1,490,841 times
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Quote:
Originally Posted by MattCW View Post
Wow, interesting! Do you know if they ever ran them in revenue service as singles or were they always in a train?
That would trip me out to see a single rail car come rolling up into the station.
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