The parallel introduction of low-floor trams showed, that with proper horizontal alignment, the gap can be small enough to be barrier-free. After the first low floor trams in Geneva of 1987, the city of Bremen asked MAN to develop a loor floor tram. The resulting prototypes of ADtranz GT6N were delivered in 1990 and mass production started in 1992 with the first batches entering service in Berlin, Bremen and Munich in the following years. The experiences with that first generation sparked interest to take further advantage of the low floor designs.