
The Pont du Gard bridge in Italy is an arch bridge. When it was being constructed, engineers likely considered how much weight would be crossing it (armies, chariots, convoys, etc). They also probably had to consider whether or not the material they were building out of would suit their needs. As for restraints, the Romans obviously had more primitive tools, and had to haul all of the stone/mortar using carts or maybe ever sledges.