Sam, the ice on the lake or river IS the bridge. they 'build' the road when they plow the snow and thicken the ice or make it stronger. the 'ice bridge' bridges two pieces of land across a lake or river with the 'ice road'. they don't actually build 'bridges' with ice. the 'ice bridge' is the road of ice across a body of water. with the super cold weather the ice has probably thickened, but they still need to plow away the snow to make the 'road'.