At one point does a long underpass become a tunnel?

[roadman65]

I was often wondering if there is a technical length of a long underpass to when it actually becomes a tunnel?  As we all know many refer to some underpasses as a tunnel such as the Benjamin Franklin Parkway overpass over I-676 & US 30 in Philadelphia or the Parking deck over the Garden State Parkway in Irvington, NJ.  Both are actual cut and cover facilities which may institute that it is only a tunnel in name rather than structural term.

Is there really a point at where a tunnel begins or does officially all cut and cover overpasses that are long, usually in urban areas to create park space like Dallas and Phoenix on their freeways still technically considered to be underpasses?   Remember some consider only a tunnel to be where the structure is actually bored under the land that its under without disturbing the land above as well.

My assumption is that anything over 100 feet in length is a tunnel or wherever it gets too dark inside where the lighting actually lights up the inside.  Even if the engineers consider it to be an underpass, if its that long than its a tunnel to me.  What are your thoughts on it and when does the academic engineering community consider to be the difference?

[empirestate]

To me it's about the construction method. A tunnel is bored, or made of constructed segments that enclose the roadway, or is a trench dug into the ground that is then covered over. A gray area would be if you constructed a structure above grade, then made a hole through it for passage (using any of the above methods). That's what you'd typically call a culvert, but if the passage is boxy enough you might be inclined to call it an overpass.

[Big John]

I believe it is 500 feet.  Foe the Atlanta airport expansion project, a runway was added over I-285.  The runway portion is considered a tunnel and needed ventilation devices installed.  The adjoining taxiway was modified so it goes over I-285 at a straighter angle in order to not have it considered a tunnel.

[dgolub]

To me it's about the construction method. A tunnel is bored, or made of constructed segments that enclose the roadway, or is a trench dug into the ground that is then covered over. A gray area would be if you constructed a structure above grade, then made a hole through it for passage (using any of the above methods). That's what you'd typically call a culvert, but if the passage is boxy enough you might be inclined to call it an overpass.

This.  The naming in some cases can be wrong/misleading.  For example, the Battery Park Underpass in Manhattan is clearly a tunnel considering that it literally goes underground.

[jeffandnicole]

The new 295 South to 42 South ramp NJDOT will be constructing will remain under Rt. 42 for about 600 feet. NJDOT considers it a tunnel, and will build it to the specifications used for a cut-and-cover tunnel.

[Pink Jazz]

Does this qualify as a tunnel?
https://www.google.com/maps/@33.3853403,-111.9066885,3a,75y,254.79h,66.22t/data=!3m6!1e1!3m4!1sAafice6dWPGirxAByAuhLQ!2e0!7i13312!8i6656

This is at the US 60/Loop 101 interchange in Tempe for traffic heading from US 60 eastbound to Loop 101 southbound.

[Pete from Boston]

This topic title makes me think of the old joke, "How far can you go in a tunnel?"

"Halfway, then you start to go out!"

[empirestate]

Does this qualify as a tunnel?
https://www.google.com/maps/@33.3853403,-111.9066885,3a,75y,254.79h,66.22t/data=!3m6!1e1!3m4!1sAafice6dWPGirxAByAuhLQ!2e0!7i13312!8i6656

This is at the US 60/Loop 101 interchange in Tempe for traffic heading from US 60 eastbound to Loop 101 southbound.

Not to me. While it has tunnel-like geometry due to the angle of the crossing, the lower roadway is really at grade, with another roadway passing over it on a structure that's built completely above the grade.

Perhaps a fundamental way to look at it is that a true tunnel passes through an obstacle, rather than over or under it. In some cases, the sense of "through" is manifested in some amount of excavation, as in an underwater tunnel or a cut-and-cover trench, for a structure that otherwise passes under its obstacle. But these cases still carry the sense of passing through the natural grade.

[SteveG1988]

How about i-95 under the apartments in Manhattan?

[jeffandnicole]

Does this qualify as a tunnel?
https://www.google.com/maps/@33.3853403,-111.9066885,3a,75y,254.79h,66.22t/data=!3m6!1e1!3m4!1sAafice6dWPGirxAByAuhLQ!2e0!7i13312!8i6656

This is at the US 60/Loop 101 interchange in Tempe for traffic heading from US 60 eastbound to Loop 101 southbound.

Much too short. There are 6 'skip' lines under the overpass. Even if the lines are 15' each, with 30' between each line, it's only about 270 feet long (45*6). Most likely, it's shorter than that; probably about 200 feet long.

[roadman65]

How about i-95 under the apartments in Manhattan?

I would say Iffy on that one. Yes its technically considered the Trans Manhattan Tunnel, but there are open areas between the buildings and where the parking deck is between Broadway and the westernmost apartment buildings its open on the sides for ventilation.

The open areas left behind, may be what not makes it a tunnel, but the constant one after the other underpasses could in sense make it a tunnel.

To me I am surprised with land and air values worth money due to demand in a city of 8 Million Plus, that someone did not try to develop the remaining openings of the expressway.  However, then a ventilation system would then be needed, but with kick backs from development and Washington funding 90 percent of it due to I-95 being interstate, that would be chomp change for both New York City and New York State.

[TXtoNJ]

I think the distinction is the primary use of the land above the roadway. If it's being used primarily as a thoroughfare, it's an underpass. If it's being used for some other purpose, it's a tunnel.

[PurdueBill]

I never believed that the "Lynnfield Tunnel" is actually a tunnel.  It's an underpass if you ask me.


This photo is from flooding of said "tunnel" in 2014; you can see that it's built as pretty much any other underpass, especially similar in shape to a SPUI underpass.  It even has two areas that are grating allowing light and air through between the u-turn ramps and the intersection...that could as well have been open air entirely but they chose to have it grating.  It's not a tunnel!

[Rothman]

Reminds me of the laughs people get around here at NYSDOT when someone asks when a culvert becomes a bridge.

[The Nature Boy]

These apartments are probably forever out of my price range but I think it'd be pretty cool to literally live over I-95.

[hbelkins]

I always assumed those apartments are some sort of public housing.

[roadman65]

https://www.google.com/maps/@40.8457334,-73.9314839,3a,75y,319.01h,67.77t/data=!3m6!1e1!3m4!1sHz8A5YxQ3N6TdP62rWJ0GA!2e0!7i13312!8i6656!6m1!1e1  Speaking of apartments and tunnels, I found the old exit to the now defunct 178th Street Tunnel next to the Trans Manhattan Apartments Tunnel at the split in ramps for Amsterdam and University Avenues from I-95 and US 1 N Bound.

[vtk]

My main criterion: when standing on the "ground" above the underpassing feature, are you standing on earth (stone and/or soil, optionally with some kind of pavement on top) or are you standing on a deck structure of some kind? The former is a tunnel; the latter is an underpass – at least, in my mind. I am aware that in some cases the distinction is not clear.

[cpzilliacus]

The state of Maryland apparently considers this to be a tunnel (I make that assertion in part because of the lane control signals approaching it, along with the lighting inside.).

[Jardine]

Where 84th street in Omaha  passed under the UP railroad embankment before the new open, airish,  multi-lane trestle was built, there was a 300' (m/l) 2 lane culvert everyone got to drive thru.

As the area around it built up, the 2 lane section became an increasing headache.  Even local businesses advertised their location relative to that 'awful tunnel'.

Now, whether or not a 300' culvert amounts to a tunnel or not, I'd think most everyone in Omaha old enough to remember it, would say that one did.

[rantanamo]

what about Klyde Warren Park in Dallas? right on the edge of tunneldom or just a long cut and cover?

[corco]

I feel like there needs to be a middle term between underpass and tunnel to describe situations where parks and buildings "cap" at grade freeways. Those definitely are not tunnels, and more accurately would fit the definition of an underpass, but calling them "underpasses" doesn't do them justice either.

[Pete from Boston]

I feel like there needs to be a middle term between underpass and tunnel to describe situations where parks and buildings "cap" at grade freeways. Those definitely are not tunnels, and more accurately would fit the definition of an underpass, but calling them "underpasses" doesn't do them justice either.

I'm not sure there does need to be another term.  "Underpass" is often used for longer runs as well as short.  The Battery Park Underpass (which is as much a tunnel as any) is a good half mile long.

[empirestate]

what about Klyde Warren Park in Dallas? right on the edge of tunneldom or just a long cut and cover?

Well it's definitely a cut-and-cover; the question is essentially whether cut-and-cover structures in general are a type of tunnel. However, I'm inclined toward "tunnel" on this one, because of what some others have said above: the use of the space above the road isn't related to the road. If they brought a bunch of dirt and built a mountain where that park is, you'd have no problem calling this a tunnel, though it would be the same structure.

[kkt]

I include cut-and-cover as a type of tunnel, if it's longer than passing under one road or railroad.