In 1999, ADEME started a national program relating to a comprehensive study on urban transports.
Several technical solutions were evaluated to quantify on a real driving condition for buses, on one hand pollutants emissions and fuel consumption, and on the other hand reliability and cost in real existing fleet.
There are two different actions types:
Actions to implement for reducing the pollution caused by existing fleet (retrofitting) using fuel modifications, Diesel particulates filters or NOx reduction system. Also these technologies were evaluated: Diesel with low sulphur content, Diesel with water emulsion, Diesel with biofuel content, five different DPF, and an EGR system will be tested (an estimation of NOx reduction was done).
New measures to be adopted when renovating a fleet, opting for vehicles whose emissions are lower than Diesel, using either of NGV (stoechiometric and lean combustion solutions with Euro II engines), or of LPG, or of hybrid bus (Neoplan, a real hybrid and Mercedes CITO, a Diesel electric engine were tested) or of electric buses.
First of all, representative driving cycles for bus were established by ADEME and industrials partners. On this cycle, pollutants were measured as well as fuel consumption, at the beginning of a program and one year after to quantify reliability and increase/decrease of pollutants emissions. At the same time, under real conditions, each technology was tested on buses fleet in use in a city. Information such as fuel consumption, lubricant analysis, problem on the technology was followed during a one year program.
This paper presents main results obtained on these urban buses. For these vehicles, same methodology was used, to set up clear comparison between technologies. An external cost comparison was done using European Cleaner Drive methodology recently set up and mains results are presented.