Sometimes traffic gets backed up while people are waiting to cross this one-lane bridge. For some reason, most people seem to thing that "one car at a time" is the best way to cross this bridge.
When there are several cars waiting, it is MUCH more efficient if you let 2-3 cars go from each direction at a time. This gets EVERYONE across the bridge quicker (except the first car in the oncoming direction who may have to wait 2-3 seconds longer at most). If everyone did this, there would probably never even be a back-up to worry about!
In places where one-lane bridges are more common - like Hawaii - it is standard to let ALL the cars going one direction to cross before the oncoming traffic does. They understand that this works out best for everyone.