The Autonomous Region of Madrid (Spain) has bought a new set of public buses to expand their network. The region currently uses B10 on a 21.5 percent of its fleet but this new set of buses are guaranteed by the manufacturer to be capable of using up to a B40 mixture (40 percent of biodiesel). The region also expects to have 50 percent of the fleet running with biodiesel, albeit B10 or B20 blends, by 2011.
Madrid also announced not long ago a new network of segregated bus routes (like in São Paulo) which would cover regional services running on CNG. The system, called Busmetro, will be fully unveiled in the near future. The city has also a set of electric mini-buses operating on small routes covering the Historic Center (as shown in the picture)
Automakers often set a limit on the highest percentage of biodiesel that can be used in diesel vehicles without voiding the warranty and that's why some manufacturers (like Peugeot) clearly state the highest percentage the warranty covers.
[Source: Autonomous Region of Madrid]