A beer bike is a pedal bike which is powered by up to 10 people. It is basically a means for partying, a bar on wheels. One of the drivers is a designated driver and does not drink.
Riding on a beer bike, you would think, would be relatively safe compared to riding, say, on a motorbike. However, it does have it dangers. Amsterdam is considering placing regulations on beer bikes. They have been banned from the red light district of Amsterdam already.