 Because the light rail network evolved from the tram network instead of replacing it, there were numerous stations served by both light rail and tram vehicles for almost three decades.While high platforms for step less entry into light rail vehicles could be built on the outer branches, stations in the city center had to have low platforms to support trams as well.The introduction of low-floor technology in the early 1990s promised wheelchair-accessible entry throughout the network without having to build several hundred high platforms.