On the commute home last night I had to wait on one of Portland's several bridges (they have 10), for the first time during my commute, when it opened to let a ship pass beneath it. The Broadway bridge is almost 100 years old yet it seems fairly new and is one of the main bridges used for bicycle crossings in Portland. I don't actually recall any annoying alarms going off. Just a little sign and two gates came down to prevent the crossing.
Just before the traffic was allowed to cross, the bridge engineer (?), spoke over a PA system to let you know that he was about to allow crossing again.
Interesting.
Later.