What about making an interchange between 2 highways, with all the bridge etc.
nt
It would be really cool.
There might also be like two level bridges which would have traffic on upper level and trains on lower level.
I think cars and rush hour traffic would be pretty cool. It really tests out the structure if there are cars in different areas on the bridge.
It would be very cool if you had to build a bridge that cost under a certain amount, but had to stand up to rush hour traffic!