The Mystic River Bridge is a type of drawbridge with counterweights which is called a bascule bridge. It’s located in Mystic, Connecticut and spans the Mystic River.
According to Wikipedia, a bascule bridge, which is sometimes referred to as a drawbridge, is a moveable bridge with a counterweight that continuously balances the span, or “leaf,” throughout the entire upward swing in providing clearance for boat traffic. Bascule is a French term for seesaw and balance, and bascule bridges operate along the same principle. They are the most common type of movable bridge in existence because they open quickly and require relatively little energy to operate.
Bascule bridges may be single or double leaf. Double leaf bridges usually have any truss structure and counterweights below the deck, while a single leaf bridge is typically a truss bridge with an elevated counterweight.
The Mystic River Bridge connects the two halves of Mystic and allows vehicles as well as pedestrians to cross from one side to the other. It opens approximately 2,200 times per year and each opening lasts about 5 minutes. From May 1-October 31, it routinely opens every hourly at 40 minutes past the hour during daylight. At any other time, it only opens on demand.