Georgia DOT eyes tunnel, double-deck for Downtown Connector

[afone]

http://www.bizjournals.com/atlanta/news/2015/04/07/georgia-dot-eyes-tunnel-double-deck-for-downtown.html

[Henry]

Get ready for the most congested tunnel (or double-decker highway) in the world!

[jeffandnicole]

The Lincoln & Holland Tunnels welcome the competition.

[DeaconG]

The Fort McHenry Tunnel says "Don't sing it, bring it"...

[cpzilliacus]

Get ready for the most congested tunnel (or double-decker highway) in the world!

Not if it is tolled and the price is set correctly (to assure free-flow conditions).

[WashuOtaku]

Get ready for the most congested tunnel (or double-decker highway) in the world!

Not if it is tolled and the price is set correctly (to assure free-flow conditions).

That is assuming that can some how convince the U.S. Congress to make a free interstate into a toll... which has never happened, to my knowledge.  Also, it's thinking outside the box, but also most unlikely options... tunnels are expensive and difficult to improve upon once built; most double-deckers that were built are now gone because they were eye-sores/costly to maintain.

In the end, they will likely add HOT lanes and improve I-285.

[xcellntbuy]

I have always been amazed at how huge Interstates 75 and 85 are through the heart of Atlanta.  Adding on top of this 12-14-lane highway are the massive ramps to and from Interstate 20.  Today, most of this land would be prime and prized real estate in the state capital.

A tunnel would be a great idea, but the width would have to be only half the size of the existing freeway.  Could a tunnel be engineered wider than six lanes?  In such a case, the tunnel would have to be an all express lane facility, undoubtedly tolled with possibly only six exits between the "top-side" and Airport sections of Interstate 285.

It may actually be better to build another Atlanta metro bypass, well around the existing metropolitan area.  There has been talk about creating one such section of highway from the northeast sections of Interstate 85 to the northwest sections of Interstate 75 with the northern metro suburbs.  With many trucks banned inside the metro bypass, Interstate 285 could use truck lanes, too.

Whatever the answers or solutions proposed, there will be a tremendous amount of money spent, well beyond the $1 billion needed right now to bring all Georgia highways up to standard.

But, in my new hometown, and the old state capital of Milledgeville, no big, big, big plans on this scale are or ever will be, in the works, but we do have many new traffic lights, nice new brick sidewalks, handicapped-accessible ramps at our hilly intersections by the Old Governor's Mansion at Georgia College and State University and the Old Capitol Building (quite a showpiece) of Georgia Military College along with some newly paved streets.  It's a nice quiet place.

[DeaconG]

Sounds like what they want to do in Texas with US 75 in Dallas (from the Mid-South thread):

http://dfw.cbslocal.com/2015/04/02/txdot-considering-underground-toll-lanes-on-central-expressway/

[codyg1985]

A tunnel would be a great idea, but the width would have to be only half the size of the existing freeway.  Could a tunnel be engineered wider than six lanes?  In such a case, the tunnel would have to be an all express lane facility, undoubtedly tolled with possibly only six exits between the "top-side" and Airport sections of Interstate 285.

I agree with this proposal. Make the express lanes subject to congestion pricing, and make it more of a thruway type facility that has less exits and is designed to move more regional and through traffic through Atlanta.

It may actually be better to build another Atlanta metro bypass, well around the existing metropolitan area.  There has been talk about creating one such section of highway from the northeast sections of Interstate 85 to the northwest sections of Interstate 75 with the northern metro suburbs.  With many trucks banned inside the metro bypass, Interstate 285 could use truck lanes, too.

I am not sure where the Northern Arc proposal is. I think it has been shelved due to fierce opposition, but it may not be dead yet. IMO, it wouldn't do anything but serve to connect the northern suburbs together (which would be beneficial), but it wouldn't serve through traffic.

I would tailor a bypass to cater to serve through traffic interests. Those seem to be I-75 en route to Florida and to Savannah, and maybe I-20 West to I-85 North.

[codyg1985]

This is kind of what I would have in mind for an Atlanta bypass system. The blue is the proposed Northern Arc, and the red is what I would propose.

[jeffandnicole]

A tunnel would be a great idea, but the width would have to be only half the size of the existing freeway.  Could a tunnel be engineered wider than six lanes?  In such a case, the tunnel would have to be an all express lane facility, undoubtedly tolled with possibly only six exits between the "top-side" and Airport sections of Interstate 285.

Why would a tunnel be limited to 6 lanes wide?  The Big Dig has a tunnel that's 5 lanes wide in one direction alone at one point. 

Sure - nearly everything can be engineered...but it's probably cheaper in the long run to divide a tunnel into several narrow sections of a few lanes wide each.  This also allows one tube to be closed for maintenance, accidents, etc, while another tube remains open. 

Anything that'll happen in Atlanta would probably be of the cut and cover variety, which is much easier to engineer than a tunnel thru a mountain or under water.  A cut and cover will only need to support an engineered park or cross streets above it.  In theory, it could support buildings as well, although that would have to be thought out before constructing the tunnel so that the pilings are in place to support such a structure.  And some simple arched beams over the underground roadway can be constructed.  To support a single 8 lane roadway those beams would need to be about 110' feet or so in length, but it can be done.

[ATLRedSoxFan]

Now might be a good time for GDOT to reconsider the resurrection of the I-485/675/GA400 big dig idea. Face it, the Downtown Connector is maxed out as is, and double-decking or tunneling would only prove to be a nightmare. And the bypasses, if people, including commerce, really wanted them, would have long been completed by now. They should have built the I-875 beltway when it was on the drawing board forty-something years ago. Even if they do build one now, it will just be hodge-podge. At least with the dig idea, it funnels the majority of the traffic where it needs to go, and gives motorist another option besides "The Downtown Connector". It would also be cost effective; not having to divert traffic back and forth.

[Henry]

This is kind of what I would have in mind for an Atlanta bypass system. The blue is the proposed Northern Arc, and the red is what I would propose.

Not a bad idea, but I would place it even further away from the I-285 Perimeter by routing it near Dallas, Newnan, Griffin and Covington.

Now might be a good time for GDOT to reconsider the resurrection of the I-485/675/GA400 big dig idea. Face it, the Downtown Connector is maxed out as is, and double-decking or tunneling would only prove to be a nightmare. And the bypasses, if people, including commerce, really wanted them, would have long been completed by now. They should have built the I-875 beltway when it was on the drawing board forty-something years ago. Even if they do build one now, it will just be hodge-podge. At least with the dig idea, it funnels the majority of the traffic where it needs to go, and gives motorist another option besides "The Downtown Connector". It would also be cost effective; not having to divert traffic back and forth.

Major opposition to the I-675 extension will hold up for the same reason as the Northern Arc, no matter how you design the highway. As nice as it would be to have new freeways built in Atlanta, it'll simply never happen. Plus the Jimmy Carter library has ruined part of those plans anyway, so there.

[xcellntbuy]

This is kind of what I would have in mind for an Atlanta bypass system. The blue is the proposed Northern Arc, and the red is what I would propose.

I really like your proposal!

[lordsutch]

Major opposition to the I-675 extension will hold up for the same reason as the Northern Arc, no matter how you design the highway. As nice as it would be to have new freeways built in Atlanta, it'll simply never happen. Plus the Jimmy Carter library has ruined part of those plans anyway, so there.

There's practically no development along the route south of I-20, and if you buried it north of I-20 as was proposed, it's just expensive but not particularly NIMBY-worthy - particularly if you don't have any exits between I-20 and I-85 to dump traffic on the local street network and just make it a through route.

Now whether that'd be cheaper than trying to dig under the downtown connector while maintaining existing traffic (cut and cover? really?) I can't really say.

As for the Northern Arc, it's probably going to be backdoor-resurrected as part of the SR 20 study, at least between I-75 and GA 400 where an east-west route is most needed. (And, of course, the proposed Sugarloaf extension north of SR 316 is resurrecting the SR 316 to I-85 leg at least.)

On the south side, I think extending SR 20 west from Hampton south of Fayetteville to Peachtree City and Newnan as a toll road is probably the most feasible proposal, since a freeway connector to I-85 from Peachtree City is overdue anyway.

[Tom958]

OK... road funding in Georgia has been inadequate for decades, and just weeks ago the multiyear scoping effort for top end 285 ended up as a project that'll add only incidental capacity, leave fifty year old bridges intact, and still cost $1 billion. Then a funding increase is passed and it's off into fantasyland. W/E.

It'll be interesting to see what they come up with. Reading what's been posted here,  I think that there's an exaggerated view of the role of long distance traffic. I suspect that rush hour flows from homes on the southside to jobs on the northside may be strong enough to make a reversible scheme worth considering, as it was for top end 285.

[The Ghostbuster]

Does anyone think this will be constructed? And how much traffic would it take off Interstates 75/85?

[codyg1985]

I would be very surprised to see it built.

[Mileage Mike]

Atlanta really should've built their outer perimeter decades ago. Now with all of the development in the north, there's just too much NIMBY-ism to ever get such a route constructed.  I've just gotten used to the fact that when I go to Atlanta traffic will always be a hellacious nightmare.

[golden eagle]

If I'm not mistaken, the Northern Arc was proposed in the '60s. I even saw a proposal from long ago for a 200-plus-mile beltway. I remember the western side would've put it near Carrollton.

[Gnutella]

Speaking of tunnels, is it possible to enlarge an existing tunnel? Has there ever been a tunnel project that's done this? Nothing to do with anything in Georgia, but it makes me die inside that the Fort Pitt Tunnel in Pittsburgh only carries two lanes in each tube because that's one of the main reasons why the highway leading to it from the west is so shitty. It makes no sense to widen the highway outside the tunnel because it'd just make the bottleneck more severe. If it's possible to enlarge an existing tunnel, then that's a good thing.

As for the Northern Arc, Gwinnett County is quietly building their portion of it, and it wouldn't surprise me if Cherokee and Bartow Counties start doing theirs eventually. If that happens, then it's really going to put the screws to Forsyth County, because they'll be pressured to connect the two unconnected segments. Eventually, I think it'd be worth it to extend Gwinnett County's segment down to U.S. 78 in Loganville.

[Henry]

Speaking of tunnels, is it possible to enlarge an existing tunnel? Has there ever been a tunnel project that's done this? Nothing to do with anything in Georgia, but it makes me die inside that the Fort Pitt Tunnel in Pittsburgh only carries two lanes in each tube because that's one of the main reasons why the highway leading to it from the west is so shitty. It makes no sense to widen the highway outside the tunnel because it'd just make the bottleneck more severe. If it's possible to enlarge an existing tunnel, then that's a good thing.

I don't think enlarging an existing tunnel would ever be possible, but adding another tube to the tunnel would be sufficient. In the Fort Pitt example, a simple boring alongside the existing tunnel would do the trick for the hypothetical widening project.

[kkt]

It's often possible to enlarge tunnels somewhat.  Many railroad tunnels have been enlarged to handle larger cars or double stacked containers.  But that's a smaller enlargement than adding lanes would be.

[ChezeHed81]

This was recently discussed in "Pittsburgh tunnel widening", referencing a project in Italy that successfully widened a tunnel without long-term closures of the tubes.

[berberry]

Add tolls to the Downtown Connector as is. Use the proceeds to build a serious commuter rail system connecting all the metro counties with the city center, charging fares low enough to be very attractive.

Atlanta has a small rail system, of course, but it could use a LOT of expansion. Atlanta could be a lot more like New York if it wants, in the sense that people could go places all over town quickly, using public transit and a little walking, which is good for all of us.