CNG-Busses in Basel - what did we Learn?
Aug. 22, 2001
In 1994 the public transport authorities of the city of Basle in Switzerland decided to run CNG (compressed natural gas) powered buses instead of conventional diesel buses as a measure to improve air quality. At the beginning of 1996, 12 CNG buses were put into service. The study provides an overview of experience with the buses during the first two years of operation and evaluates the costs and the environmental benefits. The advantages of CNG buses over conventional diesel buses with respect to air pollution are undisputed. On board measurements of NOx emissions showed levels of 5 to 6 g/vehicle-km for the CNG buses, while modern diesel buses respecting current EURO2 regulations emit about 13 to 14 g/vehicle-km. With respect to particles, a reduction factor of 10 in favour of CNG can be assumed. Direct comparative measurements of energy consumption showed a 25% higher level for the CNG buses, while operational experiences indicate that this factor can go up to +45%. The annual costs of the CNG buses were 13% higher than conventional diesel buses. This was due to higher energy consumption, higher maintenance costs, and higher investment costs for the vehicles and for the gas filling station that had to be installed especially for the buses. In the meantime the filling station has been taken over by the gas provider, which reduces the additional costs for the CNG buses to +9% and, at the same time, allows the filling station to be opened to other users. This study is a contribution to the COST/CITAIR programme: «For improved air quality in European cities».
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