Design Your Own MARTA Expansion (Atlanta, Savannah: low income, unemployed, airplanes)

[bu2]

There would be three logical routes for a Cobb line. One would be to join a Clayton line (HRT in Clayton is about as likely as HRT in Cobb anytime soon) at Arts Center. The second would be to join a Clayton line by running along North 285 and joining the red line at Perimeter Mall. The other would be to connect to the Green line instead of Arts Center.

A 4th, if we are dreaming, would be to cut over from the end of the Green line in subway across South Buckhead over to Lindberg.

[toll_booth]

Originally Posted by Born 2 Roll

Having as many as 3 different HRT lines operating along the same set of HRT tracks between the Arts Center Station and the Airport should not be a problem for MARTA.

That's because MARTA is capable of operating trains with headways as low as 2 minutes between trains.

Also, the HRT system in Washington DC (the DC Metro) operates 3 HRT lines along the same set of HRT tracks for several miles while HRT systems in Northern California (BART) and Chicago (CTA) operate as many 4 HRT lines along the same set of tracks in the geographic center of their respective networks while the HRT system in New York (the NYC Subway) operates 4 HRT lines along the same set of tracks in multiple places throughout its network.

Throughout the aforementioned HRT systems in DC, Northern California, Chicago and NYC, the transit stations served by 3 and 4 HRT lines experience headways as low as only 1 minute between directional trains during peak hours.

In the unlikely event that HRT service was ever to be implemented between Cobb County and the Atlanta Airport, the current MARTA Red Line train would be more than capable of continuing to operate between Lindbergh and the Atlanta Airport along with the current Gold Line and a future ATL Airport-Cobb HRT line.

There would be no need to discontinue MARTA Red Line service south of Lindbergh so that a future ATL Airport-Cobb HRT line could be accommodated.

True. The one concern I have, though, is what to do at the Airport station. Currently one of the platforms is for the gold line and the other is for the red line. What would they do with three lines coming into the station.

Originally Posted by bu2

Improving signaling has got to be a lot cheaper than adding new track.

Generally that is how it works.

[Gulch]

Originally Posted by toll_booth

True. The one concern I have, though, is what to do at the Airport station. Currently one of the platforms is for the gold line and the other is for the red line. What would they do with three lines coming into the station.

Stop assigning trackways to specific destinations and improve digital signage to indicate which train goes where.

[philly76miami96]

Surely, what can be done in an effort to fix the headway problem is to, after extending the lines indefinitely, end the lines in loops instead of stubs (like at Fern Rock Station on the BSL, or 69th Street or Frankford Stations on the MFL in Philadelphia). It wouldn't force trains to go backwards after reaching the terminus of a line, it would just allow them to continue in a loop towards the opposite direction. These trains, therefore, won't get in the way of others behind them. This saves the time of train operators and passengers alike.

[fourthwarden]

Originally Posted by philly76miami96

Surely, what can be done in an effort to fix the headway problem is to, after extending the lines indefinitely, end the lines in loops instead of stubs (like at Fern Rock Station on the BSL, or 69th Street or Frankford Stations on the MFL in Philadelphia). It wouldn't force trains to go backwards after reaching the terminus of a line, it would just allow them to continue in a loop towards the opposite direction. These trains, therefore, won't get in the way of others behind them. This saves the time of train operators and passengers alike.

It also essentially 'caps' the line, keeping it from easily being expanded further.

[Gulch]

Originally Posted by fourthwarden

It also essentially 'caps' the line, keeping it from easily being expanded further.

Yep. It would be incredibly shortsighted to do that.

[Born 2 Roll]

Originally Posted by MattCW

Until MARTA upgrades its signal system, even 5 mintues is frequently a struggle on the Red/Gold lines due to congestion.
As I have stated many times before, WMATA uses a more advanced signaling system to slow down trains a little bit to keep them from bunching which causes smoother operation and allows for tighter headways. MARTA still uses basic block-signaling with cab signals. Their headways along the outer portions along those lines are also not the greatest with effectively 12 minute headways outside the core.

If about $1-2 billion (or more) was to be spent to build a new HRT line out into Cobb County, one would hope that part of that money would be spent to upgrade MARTA's signaling system so that a third HRT line could operate at high frequencies along with the existing Red and Gold lines between the Arts Center and Airport stations....That's instead of discontinuing Red Line service south of Lindbergh, a move which was unpopular with the public when it was done during off-peak hours when MARTA's operating budget was being savagely cut during the 2000's and early 2010's.

Any upgrade and expansion of rail service as a whole should include the basic action of upgrading the signaling system as needed so that future expanded HRT service can be accommodated on existing tracks with existing HRT service.

Originally Posted by MattCW

BART has even worse headways of only 15 minutes on most lines with one line having ~7.5 minute headways. They also have a far more advanced signaling and control system than MARTA to the point where doors are always placed to within a few inches on the platforms.

The individual HRT lines themselves have headways of only 15 minutes in most cases, but collectively at each of the 10 stations on the BART HRT system between Daly City and West Oakland where 4 different HRT lines operate in both directions along 2 tracks, the headways between trains on all lines are as low as 1 minute along each direction of track through those 10 stations during rush hour.

Here is a link to a schedule from the West Oakland BART Station that shows headways as low as 1 minute between trains on seven different occasions during the morning rush period on the Southbound tracks (at 7:28-7:29am, 7:43-7:44am, 7:58-7:59am, 8:13-8:14am, 8:28-8:29am, 8:43-8:44am and 8:58-8:59am)...
https://www.bart.gov/stations/woak/schedule

What is even more interesting about that train schedule at the West Oakland BART Station is that there are 4 occasions where 2 different trains traveling in the same direction arrive at the station in the SAME MINUTE on the Northbound tracks during the morning rush period (at 7:00am, at 7:15am, at 7:30am and at 7:45am), effectively providing for headways of LESS than a minute on those 4 occasions.

Originally Posted by MattCW

The CTA loop is the only place they operate four lines on two tracks, but since the lines operate unidirectionally, it's effectively two lines per track which is the same as MARTA and they have comparable or worse headways.

Not all of the lines on CTA Chicago Loop only operate unidirectionally.

The CTA Green Line operates bi-directionally through the north and east portions of the Chicago Loop where northbound/westbound Green Line trains share the same northbound/westbound tracks with the Brown Line which does only operate unidirectionally (northbound/westbound) through those portions of the Chicago Loop.

On the eastbound/southbound tracks that run through the north and east portions of the Chicago Loop, the CTA Green Line operates eastbound/southbound service on the same track as the Pink, Orange and Purple lines (the CTA Purple Line only operates through the Chicago Loop during rush hour)....Which means that 4 HRT lines operate along the same eastbound/southbound HRT track during rush hour on the north and east portions of the Chicago Loop (...only 3 HRT operate on the eastbound/southbound track on the north and east portions of the Chicago Loop outside of rush hours).

Originally Posted by MattCW

Only because in those places there are four tracks rather than MARTA's two.

The sections of the BART and DC Metro systems where 3 or more HRT lines operate along the same tracks are all 2-track sections just like MARTA.

Here is a link to a picture from the West Oakland BART Station in Oakland, CA where 4 different HRT lines (the Pittsburg/Bay Point-SFO/Millbrae, Fremont-Daly City, Richmond-Daly City/Millbrae and Dublin/Pleasanton-Daly City lines) operate on only 2 tracks (1 track in each direction):
http://upload.wikimedia.org/wikipedi...n_platform.JPG


Here is a link to another picture of the West Oakland BART Station that shows the station being located along a section of HRT track where 4 different HRT lines operate along a 2-track section of HRT track:
http://www.parkingcarma.com/images/S...13723eb578.JPG


Here is a link to a picture from the L'Enfant Metro Station in Central Washington DC where 3 different HRT lines (the Orange, Silver and Blue lines) operate on 2 tracks:
http://upload.wikimedia.org/wikipedi...nt_Station.jpg

Originally Posted by MattCW

On 3:20 headways, MARTA as the system exists right now might work if nothing goes wrong and there are no delays, but until the signaling system is upgraded, it's unlikely MARTA could maintain 10 minute headways on three shared lines. One option might be to short-turn some trains like the Gold Line at the Garnett Pocket Track to reduce the chance of delays, but even then, there is still a lot of places for something to go wrong and throw the whole schedule down the toilet.

If the MARTA HRT system were ever to be expanded so that a new north-south HRT line was to come online between the ATL Airport and Cobb County, MARTA would have to do better than 10-minute headways on each of the 3 HRT lines between the Arts Center and Airport stations.

Short-turning even just one of the 3 HRT lines at Garnett would be completely unacceptable, especially with the farther-flung outlying locations in Cobb, North Fulton and Gwinnett counties (and beyond) being desperately in need of direct high-capacity transit links to the busiest airport on the planet at Hartsfield-Jackson Atlanta Int'l Airport.

Like has been expressed before, any multibillion-dollar future upgrade and expansion of the Atlanta region's high-capacity rail transit network would most assuredly have to feature upgrades to the HRT signaling system so that 3 (or maybe even more than 3) HRT lines could operate along the current 2-track section between the Arts Center and Airport stations.

Northern California's BART demonstrates that 4 HRT lines can operate on only 2 HRT tracks for many miles with headways as low as under a minute between trains on one direction of track at multiple stations.

[fourthwarden]

So, I got a bit of flack for 'ignoring Cobb', so here's a Peach Line extension into Cobb!

[Clayton white guy]

My understanding is that the Bankhead line was originally designed to service the South Cobb corridor.

[toll_booth]

Originally Posted by fourthwarden

So, I got a bit of flack for 'ignoring Cobb', so here's a Peach Line extension into Cobb!

That South Cobb line would definitely see some ridership if built. Getting Norfolk-Southern to play nice by sharing that very busy freight line with commuter rail, however, could take some prodding.