induced demand is certainly a controversial topic and far from proven in any scientific way. It is more a political belief with lots of "studies" supporting both sides of the argument.
One area that is easily measured and quantified is that cars, buses and trucks with non hybrid engines are far more efficient when cruising than when starting and stopping - by a factor of 3 or more. It is reasonable to say that 600 vehicles per hour cruising by on an overpass is far less polluting than 600 vehicles per hour in stop and go traffic on a street grid using stop lights. If induced/reduced demand cuts the number of vehicles in the area by a factor of three or more then perhaps getting rid of the overpass will result in fewer emissions as the vehicles wend their way through lighted intersections.
I don't live near the overpass but have used it on occasion. If I lived near it, I would base my stance on convenience of travel for me, beauty of the area, walk-ability, property values if I were a home owner. I would expect traffic and emissions to be worse with a congested street grid and weigh that against my other criteria when deciding whether I was for or against removal of the overpass. If I were a commuter, I would prefer the overpass. IMHO it is a political decision, not an environmental one.