depends on which bridge.
flippy
It is dropped from the purple jelly in Cellar (/join cellar) and Bridge (/join bridge).
The Jawbones are at the undead giant you can find the monster in swordhaven or in the bridge
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.
tfytstfwre is the pass
Go under the bridge
Agate Pass Bridge was created in 1950.
Matanzas Pass Bridge was created in 1927.
Marlow By-pass Bridge was created in 1972.
Deception Pass Bridge was created in 1935.
At the Crash Site, go up, to the right and then to the top right over the bridge
As of 1/1/2011, it is $6.50 each way without EZ-Pass.