Building bridges over canals can be difficult and expensive .
Maintaining the head room to allow traffic to pass its bridges up in the air with long and expensive ramp.
Bascule bridges are like draw bridges they can be opened and closed by the users. The bridges are carefully counter balanced allowing normally fit members of the public to operate them manually
There is limited Claims History as they seem to be in decline with more being destroyed rather than being built.
Such a shame.