He has 132,000 tons in motion and if the bridge isn t going to open he must put on full reverse soon enough, or carry away the bridge. If the bridge can t open, it answers with three shorts. The captain can t wait long for the answer. But the bridge operator has multiple safeguard systems. Warning gates with flashing lights lower, and, finally, a cable-net barrier blocks the road.
Safety still depends on the bridge operator s judgment.
But if he should have a stroke or faint, the whistle signal may be safeguard enough. If the operator is incapacitated after the bridge begins to open, however, it will lift all the way open until a limit switch stops it. If the operator can t bring it down, it stays up until help arrives. In an emergency, road traffic can turn around and use some other crossing, but the ships have only one road. In heavy storms, a power failure can be a threat.