No, don't go at night. Don't go unless you are part of an organized tour. Drawbridge is along the train tracks used by Amtrak and ACE trains. At night, freight trains also use the tracks, and not on a set schedule. If you are at the wrong spot and a train is coming, there is literally nowhere to go except for a swim in the mud. I went there on a tour, I think through Palo Alto Baylands. I'm not sure if tours are offered anymore, a quick google search didn't come up with anything. It's an interesting spot, especially if there is someone along who knows the history, but there really isn't that much to see anymore, most of the houses have sunk into the mud.