Down to the knitty-gritty: The practicalities of GA 400 MARTA expansion

[MattCW]

MARTA is still chugging forward with this. They've posted a newsletter, presentation, and survey to their project site. Nothing is really surprising in it, they're considering HRT, LRT, and BRT. They're also looking at a variety of routings, most of which have been batted about on here.
MARTA > About Marta > Planning

[testa50]

Originally Posted by MattCW

MARTA is still chugging forward with this. They've posted a newsletter, presentation, and survey to their project site. Nothing is really surprising in it, they're considering HRT, LRT, and BRT. They're also looking at a variety of routings, most of which have been batted about on here.
MARTA > About Marta > Planning

I voiced my support for using HRT only. Switching technologies will just make the system seem less approachable to infrequent users and add an annoying step for frequent users. Twenty years down the road when there are dense Perimeter-like clusters up and down 400, we'll be wishing we had more than BRT along the corridor. Let's do it right or not do it at all.

[toll_booth]

Originally Posted by bryantm3

Okay, so we all know that expanding MARTA up GA 400 is definitely in the cards, the question isn't if, but when. MARTA has started the process of examining the corridor and holding sessions under the Connect 400 banner, but no final or working plans have been released.

First, I want to address why this project is going to have some major challenges.
Look at the topography north of the north springs station:

The USGS Store - One stop shop for all your maps, world, United States, state, wall decor, historic, planetary, topographic, trail, hiking, foreign, satellite, digital

See all those lines? Each line denotes a 10' difference in elevation, once you get north of North Springs, it goes all over the place, especially around the Chattahoochee. Which is the second challenge. MARTA hasn't ever built over water. If MARTA is going to go up 400, it's inevitable that a big bridge building project is going to have to take place or the project dead ends at Northridge.

Another challenge is the environment— 400 south of Mansell Road and north of Holcomb Bridge is a swamp, literally, on both sides of 400. Much of the area around the Chattahoochee is nature preserves, city parks, national parks and state parks. The last challenge is probably historic and culturally significant properties, specifically around the Roswell area.

Another discussion I really think needs to happen is, what kind of a line is this going to be? Are they just going to build the line up 400 and basically put a series of stations with huge parking lots, à la North Springs, essentially building a commuter rail line? Or is the line going to take a long-term approach by building where dense development is likely to increase, and going to where people live?

I think so far the idea has been to build a commuter rail type extension up 400 to relieve the traffic situation by targetting commuters only, when I think the approach needs to be to build transit into the existing fabric so that people can get around without a car at all, if they choose to do so. I think that this would require stations in both downtown Roswell and downtown Alpharetta, in addition to major commercial sites like North Point Mall and Windward Parkway, and possibly the new Avalon development.

This will be more expensive, especially getting transit into downtown Roswell— it will have to be entirely underground, from after it crosses the Chattahoochee up to around Holcomb Bridge. Alpharetta is a lot more flexible, there is a swath of industrial land directly south of the city centre along Maxwell road, which is conveniently at a lower elevation, that leads to 400. This could potentially serve at-grade or above grade tracks, with the only underground portion of the line being in the downtown area.

There's a lot of stuff to think about but I've outlined some of these ideas in a map, with a potential idea for a line that would serve multiple purposes.

https://maps.google.com/maps/ms?msid...a51ea8aa&msa=0

I don't think the geographic challenges are as great as you may think. Except for near the Chattahoochee, the terrain is fairly level. Now, about the Chattahoochee--I don't think crossing it would be a major engineering challenge. The river is very shallow, and it's not a shipping lane, so it might not be that much more than a standard beam bridge. If the distance between pylons needs to be more than normal, well, there are plenty of engineering solutions for that.

I, too, am not so sure about a route that follows GA-9. When you start tunneling underground, the costs start to rack up, fast. The only place that's really justified is in a heavy density area such as Midtown or Downtown. Worse, the geology around here is literally rock-hard--just look at the Peachtree Center station, which doesn't even need any additional support to hold it up.

Yeah just stick with 400. This line will be a park-and-ride line first and an anchor for bus lines second. Very few people will arrive at their final destination anywhere north of Sandy Springs.

[toll_booth]

Originally Posted by testa50

Agreed 400 ROW is probably the best approach. There just isn't the residential or office density around DT Roswell to make MARTA feasible. The best approach with transit-friendly development is to make development follow the transit, rather than vice versa.

One side note: if you were to extend north of North Springs, you'll end up with a huge oversupply of parking at that station. Seems like an ideal opportunity to develop a large office complex on the adjacent piece of land, taking advantage of the existing parking and transit infrastructure.

I have had the exact same thought. If they extended the line, they'd have to build another parking garage on at least one of the northern stations, which would plummet the demand for parking at North Springs. That, or make all parking north of North Springs less than 24 hours, which would generate a nonstop stream of complaints. This really has been my number one concern with a northern

Now there is a large tract of undeveloped land just east of the station, but the city of Sandy Springs hasn't been able to attract anyone there yet. If they could find a large employer to go there, then yeah, extend that line and let customers park at North Springs. (See what they did at the Lindbergh Center for a great example of this.)

[NY2ATL2NY]

It wouldve Been Nice if GDOT left the median In between all the way up 400 into Cumming Possibly In Future anticipation of MARTA expansion. loke they did with I-66 in Washington DC for the Now Under construction Silver Line to Dulles Airport. It was Genius of GDOT
To put the Marta in the median like it is at Buckhead...Very clean and Neat Look...If it was done this way all the way up 400 all we had to do is just keep Laying track North. Instead we must meander back and forth onnthe sides of the 400 and thats IF it ever gets built...And for the Record...For the Amount of traffic comin outta the Northern suburbs to Even Consider BRT is a plain Joke...Heavy rail Should Be the ONLY option Period. You dont Throw a Bucket of water on a house fire do ya? So I say spend the Billions Once and be Done...

[cqholt]

Extension of HRT north of North Springs is the only option if MARTA wants to attract demand riders. This portion of the Red Line will need to be as fast as possible, commuter rail-hybrid system. Top-speed of 70 mph between stations. Most southbound Red Line trains are full now, imagine the ridership it would attract if it was extended to Windward Pkwy?