Quote:
Originally Posted by Andy6
What is it about a diamond interchange lets it cost only a fraction of what another interchange would cost? I would have thought the overpass would constitute the major part of the expense for any grade-separated crossing and that its cost would be fairly similar no matter what design was used. But people here seem to be claiming that a diamond costs well under half of what any other interchange would cost.
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Really it depends what the scenario is.
A diamond at Gunn for example would be one of the cheapest interchanges to build. One two lane bridge. Could probably get the bridge itself built for around $10 million. Then the next most expensive thing is concrete pavement for the roads. So again a two lane road on the bridge alignment. Then single lane ramps to/from 101. Maybe there would be traffic signals which will add another million. So $20 million is probably about right.
If it was a 4 lane road, you double it basically. If it's a big interchange like 59n/101, it's 250 million with all the highway work they did.
Bridge length also makes it more pensive though. If we're planning for 6 lanes underneath, the girders are long and more expensive. So maybe Gunn is $25 million.
Maybe Biff has some estimates or cost from recent works. What did the roblin/100 reconstruction cost? That's got to be public information.