It is safe to pass only when you are not entering the bridge and there is no oncoming traffic. It you do not have enough time to pass before a bridge wait until after you have crossed the bridge to pass.
Go under the bridge
Matanzas Pass Bridge was created in 1927.
Marlow By-pass Bridge was created in 1972.
Agate Pass Bridge was created in 1950.
Deception Pass Bridge was created in 1935.
depends on which bridge.
Draw bridge
No it doesn't. Tower Bridge can open to let boats pass under it.
The middle of the bridge opens to let boats pass
Tower Bridge is the only bridge in London that is capable of opening to allow ships to pass under it.
it is called a draw bridge