5.2 City buses
Mini buses, standard buses and articulated buses are used for urban public transport and have different dimensions, total weight and engine power. A standard city bus with a net weight of 15 t will be exemplified.
Diesel buses dominate the global share of buses to date, while other fuels like CNG and LPG as well as bio-diesel are less significant. The fuel consumption of buses differs with the geographical environment, the traffic situation and the distance between stops, not only between, but also within cities. Based on the analysis of data from transport operators, a fuel consumption of 40 l diesel fuel per 100 km will be assumed for ex- emplification [IFEU 2002].
5.2.1 Specific energy savings
No studies based on tests or simulations on the specific fuel savings for city buses have been found. Values stated by the bus manufacturer MAN as well as the Associa- tion of German Transport Operators (“Verband Deutscher Verkehrsunternehmen” (VDV)) in Tab. 5 are estimates on the basis of expert judgement.
Tab. 5: Specific and relative fuel savings of city buses
Specific fuel savings [l/(100 km*100 kg)]
Relative energy savings [%/10 %]
[MAN 2002] [VDV 2002]
Extrapolation with data from [INFRAS 1999b]
0.2 0.1 – 0.2 0.1
7.5 3.75 – 7.5 3.75
In addition to these sources, an extrapolation of the fuel consumption of empty and full city buses, based on data from [INFRAS 1999b], has been undertaken. The value of 0.1 l/(100 km*100 kg) is in the same range as data from [VDV 2002], but has uncer- tainties in the number and weight of the passengers. Taking into account all sources, a value of 0.15 l/(100 km*100 kg) will be used for exemplification. Relative energy savings have been calculated based on the assumptions for our exemplification (40 l fuel con- sumption and 15 t weight). The values between 3.75 and 7.5 % fuel savings for a 10 % weight reduction of standard city bus are in the same range as the relative energy sav- ings for passenger cars with axle transmissions.
5.2.2 Life-time performance and energy savings
The annual performance of a standard city bus in Germany has been estimated in the range between 50’000 and 80’000 km ([MAN 2002], [VDV 2002]). On the assumption of a life-time of 8 to 15 years, the life-time performance will be between 0.4 and 1.2 Mio. km. The U.S. Bureau of Transport Statistic ([BTS 2002]) states a long time average age of more than 8 years for full size transit buses in the U.S. which is equivalent to a life- time of about 16 or 17 years. City buses of the Berlin municipal transport services ([BVG 2002]) operate between 12 – 14 years and achieve a life-time performance of