In 1995 a system of 300 bicycles using coins to unlock the bicycles in the style of shopping carts was introduced in Copenhagen. It was initiated by Morten Sadolin and Ole Wessung. The idea was developed by both Copenhageners after they were victims of bicycle theft one night in 1989. Copenhagen's "ByCylken" program was the first large-scale urban bike share program to feature specially designed bikes with parts that could not be used on other bikes. To obtain a bicycle, riders pay a refundable deposit at one of 100 special locking bike stands, and have unlimited use of the bike within a specified 'city bike zone.' The fine for not returning a bicycle or leaving the bike sharing zone exceeds US$150, and is strictly enforced by the Copenhagen police. Originally, the program's founders hoped to completely finance the program by selling advertising space on the bicycles, which was placed on the bike's frame and its solid disc-type wheels. This funding source quickly proved to be insufficient, and the city of Copenhagen took over the administration of the program, funding most of the program costs through appropriations from city revenues along with contributions from corporate donors. Since the City Bikes program is free to the user, there is no return on the capital invested by the municipality, and a considerable amount of public funds must constantly be re-invested to keep the system in service, to enforce regulations, and to replace missing bikes.