The first of Viennas 20 new environmentally-friendly air-conditioned buses have begun operating on a trial basis on route 57A. Powered by liquid natural eco-gas, the buses already undercut the European 2008 Euro 5 emission standards by more than half. Other features of the new buses include more efficient door-opening times and a special high-tech engineering system that lowers the vehicle to ground level at stops to allow low-access for people who are mobility-impaired. The Wiener Linien public transport system in the Austrian capital and MAN Commercial Vehicles have been awarded the City of Vienna Environment Prize for the new buses.