A combination of an effective public transport system and minimum use of cars is the cure for climate change in cities like Mumbai and Kolkata, according to a noted British scientist.

"We should strive for minimum use of cars and give more emphasis on building an effective public transport," said David Banister, Professor of Transport Studies in Oxford University while delivering a lecture on transportation systems and climate change.

About 40 per cent of the world's cities are located on sea shores and these cities, such as Mumbai, Kolkata, Chennai, Colombo or Bangkok, are under threat due to global warming, he said.

"Fifteen of the 20 mega cities lie on the coast. Asian mega cities like Mumbai, Kolkata, Chennai, Karachi and Bangkok are under risk of flooding if the temperature increases by another two degrees," Banister said.

In this situation, "Priority should be given to high quality public transport, cycling and walking. The role of the car in the city may be limited to ultra clean electric or plug-in hybrid vehicles powered by renewable energy," the scientist said.

"Residents with good access to public transport own 10-30 per cent less cars, drive 10-30 per cent fewer miles, use alternative models 2-10 times more frequently," banister pointed out.

In London, he said, a congestion charge has been put on all large vehicles which is in turn used to buy new buses and create better public transport. Pollution through traffic can be reduced by shortening travel time and more efficient land use, he added.

Experiments with car-free housing complexes with public transport at the door step, areas in busy city intersections being converted into 'public transport only' zones, cycling routes and extra congestion and parking charges on large and fuel inefficient cars have shown promising results in London, he said.

The real challenge confronting the developing cities is the expected growth in travel from all cities and the desire for longer distance travel.