Seesaws for giants: Chasing Chicago’s movable bridges
Chicago is a city of bridges but, more importantly for that one weekend day in April 2011, Chicago is a city of movable bridges.
Every spring, a few times a week, twenty-seven bridges open in sequence to allow the boats to get to the lake… and every fall that sequence is reversed.
As I found out, it wasn’t entirely an illusion. Most of the bridges match their road decks with carefully balanced counterweights — either visible above or hidden below the ground — and the motor is required only to tip it gently one way or the other.
This type of bridge is called a bascule bridge — French for “balance scale” which operates the same way. Here’s one example with a visible counterweight although this particular bridge, at Cermak Road, works a bit more like a rocking chair than a seesaw:
We were following the same route four different teams of operators did, leapfrogging each other in vans for maximum efficiency.
