Water taxis queuing to enter the Grand Canal, Venice. Its not really something I had thought about, but once I had noticed them queuing, I saw it happening everywhere, going across to the islands, they have to queue. Even the gondolas have to wait on traffic lights to enter some of the really small canals.
Venice Italy – October 2016
Echoes of the Past 
That’s a new thought..traffic light for boats. I can imagine that it is needed as with any other source of transportation.
Yes, because their roads are waterways, the same as roads with all the lights and road signs…..just took a while to notice 🙂