I was taught that it went back to the days when ships were dependent upon the wind and tides to move up and down rivers. Delaying them could be catastrophic, both literally and in the economic sense. Everybody acknowledged their need to go while the gettin’ was good.
I stumbled across this video by chance, showing a freighter moving through Miami to reach its port, with 8 draw bridges being raised to let it pass:
Here ya go. At the bottom of the article are tiny animations showing the way various moveable bridges move.
On railroads the maintenance of way (MOW) equipment can putter about the tracks on their own but to move an appreciable distance to the next job they are loaded onto track-equipped flatcars. To facilitate the loading, the last flatcar in the string has a ramp, called a scorpion, that unfurls from the top of the car down to track level, making a ramp. It is not as elegant looking at the Heatherwick bridge when it moves, though.
The video is queued to where the last of the equipment is loaded and the ramp curled up. If you want to see the entire MOW parade, back up to about 3:40. A couple had to make two tries to get up the 7% grade and one tie-grabber used its tie-grabbing arm to crutch its way aboard.
Neat video – thanks. I was tickled by the port-a-potty on the small trailer.
Bruan
Sadly, they don’t show the hydraulic wench. I would have liked to have seen her.
Strange women lying in ponds distributing swords is no basis for a system of track maintenance.
Your comment reminded me of the pneumatic female characters in a SF story whose details I don’t recall. And which IMO almost brought the term “pneumatic” into general use for attractive women.
Somebody here will know which story I’m talking about.
Brave New World
Montreal’s Victoria Bridge(s) has four sets of lift bridges - two for road, and two for rail - over the St Lawrence Seaway canal. The way the bridges are arranged - road and rail traffic never needs to halt, so that the bridges (one set or the other) can be raised on demand when ships require it (they are passing through a lock between the two sets of bridges).
I don’t know what happens in winter, when the canal may freeze, and ship traffic is infrequent. I assume an attendant would be available if a (rare) ship needs to pass after advance notice. (it usually closes for a couple of weeks in mid-January).