The Citybike Wien system is a free bike system. You can hire a bike at 61 stations across Vienna and return it at any other station, 24 hours a day, 7 days a week. The first hour of every ride is free of charge. Before hiring a Citybike you need to register either with a credit card (Visa, MasterCard, JCB) or a Citybike tourist card - at the terminal of one of the stations or on the internet. You can find the general traffic rules for bikers here.