How Much does it cost to replace an at-grade intersection with an overpass?

[jeffandnicole]

If one of the roads is significantly below grade, that is one road "tunnels" under the other, you need a pumping system to prevent flooding.

And with the additional pavement required by the diamond interchange, many areas might require construction of an adjacent pond or some other form of stormwater mitigation. A good thing, IMHO.

This is something that is studied on every project and can increase the cost a lot! SR 37 in Fishers, IN had an over 1 million dollar cost increase due to drainage changes. Also a rule 5 permit is required and that is drainage related.

Most grade separation projects cost tens of millions so an extra 1 million for drainage isn't that big of a deal.

It is when that increase happens after construction starts. [emoji15]

You'll be surprised how normal that for large projects.

It also draws into question why this wasn't engineered properly in the first place.

And I'm guessing Rule 5, whatever that is, is something related to the state you're referring to.

[mgk920]

In a congested and busy commercial area, right-of-way acquisition could well be the #1 cost item.

Mike

[kernals12]

In a congested and busy commercial area, right-of-way acquisition could well be the #1 cost item.

Mike

I thinking of suburban arterial streets which already have an absurd number of left turn lanes.

[kphoger]

I thinking of suburban arterial streets which already have an absurd number of left turn lanes.

Residents probably wouldn't much care for an elevated bridge in that environment, so you'd probably be looking at sinking the lower roadway below grade–in which case the previous comment about flood mitigation definitely comes into play.  Land acquisition will likely include strips of each property along the affected roadway–whether elevated or sunken–even without ramps, which you've already said would be in the plan.  A plan will need to be made for access to the properties that will no longer have direct access to the affected roadway(s).

One alternative that might be more cost-effective (but also might have lower capacity) is a grade-separated quadrant intersection.  See IL-38/IL-53 and IL-83/IL-19 in suburban Chicago as two examples.

[jeffandnicole]

One alternative that might be more cost-effective (but also might have lower capacity) is a grade-separated quadrant intersection.  See IL-38/IL-53 and IL-83/IL-19 in suburban Chicago as two examples.

Technically, capacity is higher because traffic can free-flow at these intersections.  It would need to be considered where an intersection can be placed that will allow access between both roadway, if it ultimately is a plus or minus for capacity in the entire corridor.

NJ actually built a number of these back in the day, when the money was flowing and things could really be squeezed in.  https://goo.gl/maps/quEvoqGr8Mymo5M27 is one such example, in which the cross street became RIROs, and a very small bypass allowed for free-flow movements, while 130 wasn't interrupted at all.

[kernals12]

I thinking of suburban arterial streets which already have an absurd number of left turn lanes.

Residents probably wouldn't much care for an elevated bridge in that environment, so you'd probably be looking at sinking the lower roadway below grade–in which case the previous comment about flood mitigation definitely comes into play.  Land acquisition will likely include strips of each property along the affected roadway–whether elevated or sunken–even without ramps, which you've already said would be in the plan.  A plan will need to be made for access to the properties that will no longer have direct access to the affected roadway(s).

One alternative that might be more cost-effective (but also might have lower capacity) is a grade-separated quadrant intersection.  See IL-38/IL-53 and IL-83/IL-19 in suburban Chicago as two examples.

If the arterial is lined with strip malls and car dealerships, I don't think they'll care.

[jeffandnicole]

I thinking of suburban arterial streets which already have an absurd number of left turn lanes.

Residents probably wouldn't much care for an elevated bridge in that environment, so you'd probably be looking at sinking the lower roadway below grade–in which case the previous comment about flood mitigation definitely comes into play.  Land acquisition will likely include strips of each property along the affected roadway–whether elevated or sunken–even without ramps, which you've already said would be in the plan.  A plan will need to be made for access to the properties that will no longer have direct access to the affected roadway(s).

One alternative that might be more cost-effective (but also might have lower capacity) is a grade-separated quadrant intersection.  See IL-38/IL-53 and IL-83/IL-19 in suburban Chicago as two examples.

If the arterial is lined with strip malls and car dealerships, I don't think they'll care.

They may care more about the lack of access to the main road if it's cut off.

But people are funny.  They'll also say it'll lower their property value, even if their siding is falling off, the neighbor across the street had 3 junkers sitting on the front lawn, and they have no plans on moving, ever. 

[froggie]

One huge cost item that has not been mentioned yet, and often dwarfs mgk's argument about right-of-way costs being #1, is traffic control.  Maintaining traffic through a construction zone, especially one with complex project phasing, is costly.

[Dirt Roads]

One huge cost item that has not been mentioned yet, and often dwarfs mgk's argument about right-of-way costs being #1, is traffic control.  Maintaining traffic through a construction zone, especially one with complex project phasing, is costly.

Nowadays, the primary type of phasing is nightly shutdowns.  This forces the hourly wages up and limits the work hours to usually a five or six hour window.  We were fortunate that NCDOT was able to completely shut down the section of (then) Green 40 through Winston-Salem to redevelop the US-421 Salem Parkway at a reasonable cost.

[froggie]

Not everyone does nightly shutdowns.  I live in a state where, except on a handful of roads in one county, they almost never do overnight closures or night work.

[cbeach40]

Not everyone does nightly shutdowns.  I live in a state where, except on a handful of roads in one county, they almost never do overnight closures or night work.

Reasons for that are in my experience to minimize noise impacts on the surrounding residences, or to minimize costs as labour costs tend to have a premium on overnights/weekends. But that latter is balancing costs, whether it's necessary for the staging to have lower traffic volumes or to have the work done sooner (though ultimately within the same number of working days, so sooner isn't likely to save you anything there).

[silverback1065]

I thinking of suburban arterial streets which already have an absurd number of left turn lanes.

Residents probably wouldn't much care for an elevated bridge in that environment, so you'd probably be looking at sinking the lower roadway below grade–in which case the previous comment about flood mitigation definitely comes into play.  Land acquisition will likely include strips of each property along the affected roadway–whether elevated or sunken–even without ramps, which you've already said would be in the plan.  A plan will need to be made for access to the properties that will no longer have direct access to the affected roadway(s).

One alternative that might be more cost-effective (but also might have lower capacity) is a grade-separated quadrant intersection.  See IL-38/IL-53 and IL-83/IL-19 in suburban Chicago as two examples.

If the arterial is lined with strip malls and car dealerships, I don't think they'll care.

They very much care in many situations. even can kill the project. you hear things like "business will go down due to construction" or "permanent loss of business due to loss of access" US 31 in Carmel, IN actually killed 3 strip malls due to lack of access.

[Dirt Roads]

Not everyone does nightly shutdowns.  I live in a state where, except on a handful of roads in one county, they almost never do overnight closures or night work.

Reasons for that are in my experience to minimize noise impacts on the surrounding residences, or to minimize costs as labour costs tend to have a premium on overnights/weekends. But that latter is balancing costs, whether it's necessary for the staging to have lower traffic volumes or to have the work done sooner (though ultimately within the same number of working days, so sooner isn't likely to save you anything there).

In my youth, it was not unusual for contractors to hang stringers over top of an operating roadway.  Oops (not smart).  Most bridge projects would prefer to schedule about one work week of unobstructed access per span over an existing thoroughfare.  Obviously, they can do this faster but it is becomes a big logistics puzzle (with multiple backup plans).  But there's any number of ways to get unobstructed access.  Once upon a time in West Virginia, the DOH would construct temporary ramps to the elevated section of crossroad and use them as construction detours (and remove them afterward).