"Every time the doors are held open, this delays boarding and alighting with direct consequences for the entire line operation," was the reason given. "In addition, blocking the closing process can be dangerous." Anyone still standing in the door area after the door signal has sounded is at risk of being trapped or injured. BVG also wants to prevent door damage in this way. "On average, there are around 200 door malfunctions per month in subway operations alone - many of them caused by deliberately holding doors open." The subsequent necessary repairs mean that the train is then missing from the route network.