It's been 60 years since I visited the bridge tender on the Martinez bridge, so my recollections may not be accurate I remember a light or bell notifying that a train was going to approach the bridge. Just as important is that the bridge's lift span had to be open something like 20 minutes before any train in the area wanted to cross. Trains just had to wait as marine traffic had authority. Those big ships needed a clear lane and having to stop on the Carquinez Straits was not a simple matter. I sorta remember the bridge tender had a daily ship movement lineup with the approximate times a ship would show up, but it was up to the bridge tender to be alert for a ship at any time.