What if: Freeway & Urban Park/Trail/Neighborhood connectivity via Land Bridges (Atlanta: neighborhoods, construction)

[Need4Camaro]

What if sections of Urban Freeway, and possibly even suburban.. were to be submerged underground in brief intervals, typically in areas where there is sufficient space between exits .. or removing some interchanges altogether (while also upgrading interchanges prior to or just after the eliminated interchange to handle the extra traffic) … The submerged sections would submerge under a land bridge which would incorporate parks, trails and methods of walkability across the freeway, reconnecting neighborhoods in between. Along the corridor of the freeways would be urban trails similar to Path 400, only they would not cross freeways at major interchanges but rather land bridges keeping pedestrian and automotive traffic as separate as possible while also providing links between neighborhoods and walkability between them. This would also provide a cooridoor of walkable / bikeable trails that follow and cross the freeway at certain bridges which will act as a branch system that connects neighborhoods within the vicinity of the highways.

Thoughts?

[aries4118]

Originally Posted by Need4Camaro

What if sections of Urban Freeway, and possibly even suburban.. were to be submerged underground in brief intervals, typically in areas where there is sufficient space between exits .. or removing some interchanges altogether (while also upgrading interchanges prior to or just after the eliminated interchange to handle the extra traffic) … The submerged sections would submerge under a land bridge which would incorporate parks, trails and methods of walkability across the freeway, reconnecting neighborhoods in between. Along the corridor of the freeways would be urban trails similar to Path 400, only they would not cross freeways at major interchanges but rather land bridges keeping pedestrian and automotive traffic as separate as possible while also providing links between neighborhoods and walkability between them. This would also provide a cooridoor of walkable / bikeable trails that follow and cross the freeway at certain bridges which will act as a branch system that connects neighborhoods within the vicinity of the highways.

Thoughts?

I like.

[T Block]

Interstate highways have long transitions for both vertical curves and horizontal curves. So a brief tunnel area is not likely.

Basically, just build more bridges or widen bridges. Of course the 5th Street GT bridge is an example.

I like 304L pedestrian bridges. Build one at Peachtree Ave across Peachtree Rd and build one at Maple Dr across Peachtree Rd. There is an existing concrete pedestrian bridge across HWY 400 to Lenox Square.

Oh, there's another pedestrian bridge over HWY 400 at Tower Pl Dr.

Strangely enough, there is a pedestrian tunnel to the Walmart on PIB.

And there's a pedestrian tunnel between Piedmont Hospital and the 2001 Building.

Oh, there's a pedestrian tunnel under I-85 at Mayson St.

I think that pedestrian tunnels are winning here.

[T Block]

The construction for the fifth runway at the Atlanta airport might give some ideas:

https://www.walshgroup.com/ourexperi...tructures.html

[Need4Camaro]

True about the transitions / grading, however; there are many freeways in Europe (especially in Spain and Italy) that instead of curving around hills, they make relatively short tunnels right through them. I think what could be done instead is use the topography to our advantage, meaning instead of the road following certain hills, instead, tunnel through it while keeping the road relatively level, leaving the top of the hill intact for nature trail and even park use. There are many rolling hills where this can be utilized as so the road will not need to dip or elevate but remain relatively level as it travels through hills. Since we develop on hills on the surface level, the tops of these hills will still be uniform with adjacent development as well.

[T Block]

Well, here's a link to a tunnel construction:

https://en.wikipedia.org/wiki/State_Route_99_tunnel

But there's not much room in a tunnel. Compare to new sections of interstate highway, like the Birmingham bypass, that have wide lanes and wide shoulders and those are just pleasant to drive.

[Need4Camaro]

The freeway width would definitely be a concern for tunneling. Although keep in mind these tunnels I’m proposing wouldn’t be anywhere near as long as Alaskan Way (I used to commute on that road. Miss that highway.) They wouldn’t really be much longer than say 6x the length of an average overpass. They would just be frequent passes under the ground rather than a long project under neighborhoods, which would be direly expensive given the granite composure of the underlying Earth.

If the width is still an issue then let’s take it a step further…

An ordinance called the commute belt which would enforce employers within the ITP district to rethink commuting options for their employees. The official belt would be the I-285 bypass. Employers who hire outside of the I-285 area would need to pay an infrastructure tax if their employee is capable of remote work but the employer chooses to have them commute. If the employer / employee relationship is not capable of remote work then there would be no tax. Ideally this would reduce traffic demand on major interstates which would inadvertently justify the ability to reduce lanes and reclaim adjacent areas to interstates as walkable / bikeable trails with the intent of walkability to reconnect neighborhoods between highways without interference between automobiles (using said land bridges)…

Employees employed within the ITP area can still commute with no tax to the employer as ideally they would be supplemented by more transit options rather than driving.

[T Block]

I worked out a project design:

Well, getting traffic into and out-of a tunnel, that has stacked directional lanes, would be a difficult transition for short distances. Or two side-by-side tunnels would be subject to a larger geological load than two tunnels spaced apart. But spacing two tunnels apart would require changing the layout of the highway.

And the design at the ATL 5th runway is taller than needed but also requires extremely large amounts of horizontal beam strength.

So the solution is lower concrete walls at the sides of the highway shoulders. Then a series of 304L extrusions would make an arch shape between the tops of the walls and along the lengths of the walls. Next, 304L sheet-metal, or formed plate, would rivet between the arch shape extrusions. Finally, fill-dirt on the outsides of the walls would fill up to the height of the top of the arch shape and form around the arch shape. Then the build simply makes a green space on top of the highway but with a reasonable amount of geological weight to support. Also, the design avoids the dead-weight of concrete in the arch shape.

Now the fill-dirt would not form around the arch shape at each end because a 2-to-1 side-slope would be needed. Or 304L lateral wing-walls could be constructed along the first and last arch extrusions but most likely just hold the bottoms of the side-slopes and not hold a full amount of shear cut of dirt-fill.


A similar construction could be done with a flat top but large amounts of horizontal beam strength would be needed. A couple of feet of fill-dirt would go squarely on top of the flat top.

[T Block]

The arch-shape construction has a more economical use of materials than a flat top.

But I think we are back to pedestrian bridges and pedestrian tunnels so that neighborhoods on each side of a highway can stroll between each other.

[arjay57]

Originally Posted by Need4Camaro

The freeway width would definitely be a concern for tunneling. Although keep in mind these tunnels I’m proposing wouldn’t be anywhere near as long as Alaskan Way (I used to commute on that road. Miss that highway.) They wouldn’t really be much longer than say 6x the length of an average overpass. They would just be frequent passes under the ground rather than a long project under neighborhoods, which would be direly expensive given the granite composure of the underlying Earth.

If the width is still an issue then let’s take it a step further…

An ordinance called the commute belt which would enforce employers within the ITP district to rethink commuting options for their employees. The official belt would be the I-285 bypass. Employers who hire outside of the I-285 area would need to pay an infrastructure tax if their employee is capable of remote work but the employer chooses to have them commute. If the employer / employee relationship is not capable of remote work then there would be no tax. Ideally this would reduce traffic demand on major interstates which would inadvertently justify the ability to reduce lanes and reclaim adjacent areas to interstates as walkable / bikeable trails with the intent of walkability to reconnect neighborhoods between highways without interference between automobiles (using said land bridges)…

Employees employed within the ITP area can still commute with no tax to the employer as ideally they would be supplemented by more transit options rather than driving.

I am okay with it but I don't see why it should limited to 285.