Marianne Kearney, Jakarta – Originally imported from India in the 70s as a faster alternative to the motorised rickshaw, the bajaj – similar to Thailand's tuk-tuks – was never officially legalised in many parts of Jakarta. However, these brightly coloured vehicles are as much a part of Jakarta's street scene as the trishaw and have multiplied over the years – 20,000 of them now ply Jakarta's markets and back alleys.

They are also a key contributor to air pollution in Jakarta. Environmental campaigner Ahmad Syafrudin, who has been campaigning to phase out heavily polluting fuels, welcomes the introduction of vehicles using alternative fuels. "We agree with using CNG because it cuts out a lot of pollution," he said. CNG refers to compressed natural gas.

Mr Syafrudin said Jakarta rates as the world's third- or fourth-most polluted city in the world, largely because unlike other Asian cities such as Bangkok, it has yet to ban leaded fuel.