Environmental requirements in tendering procedures for buses are intended to reduce the significant pollutant, greenhouse gas and noise emissions occasioned by buses, particularly in urban environments and areas in need of protection. Hence the requirements recommended in this guide apply to buses used for urban transport, but can also be used for interurban and long-distance buses. These requirements apply to all buses with internal combustion engines (i.e. conventional buses), electric buses, and hybrid buses. Quelle: http://www.umweltbundesamt.de/
