I’ve noticed for a while that new overpasses being constructed for new or existing highways along existing arterial roads usually have the new overpass built offset from the existing road. I know this is to reduce/prevent disruptions as closing an existing overpass (closing an old 2 lane overpass to build a new 4 lane one) or through-fare is not the best decision, but what about new highways?
I’m mostly talking about Highway 407 East here but others still apply, why build a new overpass (with capacity for 4 lanes) that slightly curves around the existing road (which is at grade) and moving traffic to the new slightly diverted overpass instead of building a temporary road, move traffic to new road, demolish the existing road, build a new overpass, move traffic to new overpass, demolish temporary road?
Is it not worth the cost of building and demolishing the temporary road to avoid having a curve in the new road on approach to the new overpass?