(About 40 minutes in) When the Croat hits the walker with his car, the walker goes under the car with its head sitting just under the bumper. When the Croat gets out of the car, the walker's head is now behind the driver's front wheel.
When Croat enters the opera and the camera faces him with the door into the street on his background, there are cars in the street visible going back and forward.
The storm drains in the sewers are all open and not sealed, as evidenced by the light shining through them into the sewer tunnels. Methane is lighter than air, and would accumulate at the top of the sewer tunnels. Without the storm drains being sealed, a large percentage of the methane would leak out of the drains.