This is where pre-mapped roadways help. Just an internal GPS database sent down to your car that says "Hey, at this GPS coordinate, there's a bridge here. Here'

This is where pre-mapped roadways help. Just an internal GPS database sent down to your car that says "Hey, at this GPS coordinate, there's a bridge here. Here's how to navigate over it." Everywhere else the cars can use radar+camera. GM (SuperCruise) and Ford (BlueCruise) do this today.