The barrier faces or a barrier to block If the car in front stops pending before it, next stop later, respectively. When I turn it on and let the car stalls stop waiting for the follow up.
The function block Or has a barrier blocking. If the car ahead must wait before their turn and proceed respectively. When opening a barrier, then the car stops moving forward as well.
The meaning, function can block or the block wall If the car in front stopped waiting before it stopped the car and later, respectively. When you open the wall and car stop moving along.