look at a skyline, and double that.
If you want go to 2.5 times
It may be taller than the tallest bit, but youll also have some room for antenna celarance.
And about hte incline, just make a gradual incline on the track up to the bridge....its a more antural feel and pretty cool too
Or if you feel like being twisted, make the road dip under hte bridge, and see what kinds o wrecks come out of it