[aidenn0]

The expansion is as a fraction of length. For steel its around 10-20ppm per degree C.

So a 40 degree temperature swing would be 400-800ppm, which means about 1mm difference in length for 2m of steel. Obviously bridges aren't usually made of a single span of steel, but there will be limits to how much expansion a given joint can tolerate, and each half of a draw-bridge needs to be fairly rigid. On top of that, 40 degrees is probably much less than the difference in road temperature between a cold night in January vs. a sunny day in August.

Railway tracks used to buckle in the heat before they built them with a small gap between the rail spans.