I don't think the current rail tunnels are at capacity, so there's no need for additional ones. In my point of view, the Gordie Howe bridge is more about building in redundancy at a key transportation bottleneck, as well as having a gov. controlled bridge not subject to the whims of one [[unstable and litigious) man.

The 94 expansion is as much about car traffic as trucks. Stand on Woodward over 94 at it's bussiest and it's mostly passenger cars, not trucks. Of course, we could take some of these cars off the road with comprehensive rapid transit, but that's been talked about to death here and not the topic at hand.

Americas freight rail network is one of, if not the best in the world. Businesses already use it extensively to transport goods, particularly multimodal containers to the extent they can. Trucks will always have a large part to play though getting products from the rail yards to warehouses or retail.