When you step out into the chaos of a central Delhi street – with its dilapidated looking buses, battered taxis and auto-rickshaws fighting for space, it is hard to believe that Delhi has carried out one of the largest experiments in the greening of urban transport anywhere in the World.

But since 2002 all buses (10,000 of them), auto rickshaws and taxis have been converted to Compressed Natural Gas.

The moves to convert to CNG were brought in alongside other measures – including a reduction in the most polluting industries, the cleaning up of power stations, and a reduction in the sulfer content for diesel vehicles.

The measures were forced through by the Indian Supreme Court rather than the politicians – and were designed to deal with Delhi’s chronic air pollution (among the worst in the World) rather than carbon.

Although these changes were about air pollution rather than carbon, it struck me that if Delhi can take such dramatic environmental steps, with all the chronic social challenges it faces, then there’s no reason why the challenge of carbon reduction should result in the levels of fatalism that it seems to do in the UK.

As you sit in a pub in Britain (usually with the heat leaking out of the ill-fitting windows) the usual take on climate change seems to be a deep sense of hopelessness over the scale of the task. China’s power stations, the feeling that policy change in this country never happens quick enough, both combine into a sense that we are not going to go down fighting on this one.

I don’t get it. Why the assumption that nothing will change when things change anyway? There’s plenty of evidence that technologies turn over quickly and dramatically once they reach a critical mass. You can see it time and time again from modes of transport to energy sources. The rapidity of the turnover that can occur from economic factors alone can be extremely rapid: canals to railways, steam to diesel, rail to road.

The other reason not to be fatalistic is that I sense the carbon debate is moving on. Its moving on from an argument about whether climate change exists or not, and from high level rhetorical commitments and the odd gesture here and there. It’s now about a practical challenge. If we need to reduce carbon by a set amount then what’s the most timely and most cost effective way to do this within the time available? In other words its not about polar bears and culture wars anymore it’s a practical, behavioural and technical challenge.

Having said that from a public transport perspective (which is where Ive been involved) it’s a very tricky challenge however.

The first challenge is how you measure carbon emissions and allot them to particular modes and journeys. The carbon output of a bus journey for example depends on vehicle type, the condition of the vehicle, the number of passengers, and the way its driven. Telling people what the carbon footprint of the journeys they make by public transport therefore has to be based on assumptions and aggregations piled on assumptions and aggregations.

The second challenge is that if you make public transport greener and reduce its carbon impact the chances are that you’ve also made it more attractive (eg you’ve provided new vehicles) and thus people adapt accordingly (by for example making more or longer journeys).

The third challenge for public transport is that a) the vehicles that provide it are large and heavy and thus harder to convert to low carbon technologies than light weight vehicles like cars b) the car market is far larger than the public transport vehicle market and thus the likely focus for investment for low carbon technologies is the car market.

Given the complexities and relatively small share of overall carbon outputs attributable to public transport the major influences of UK carbon policy (such as the Climate Change Committee and Lord Stern) tend to prioritise more straightforward targets for carbon reductions – such as power generation and the carbon efficiency of the built environment. And when they get to transport they tend to go for what looks to be the easiest hit – which is decarbonising the car fleet.

To a certain extent there is a justification in focussing on non-transport sectors as priority sectors. However, given the scale of the carbon reduction needed – and the relatively short timescale – transport needs to play its part.

A report by MTRU for Campaign for Better Transport also makes the argument against too much focus on a ‘tech-fix’ for carbon reduction from transport. There’s no doubt that we need to reduce carbon from vehicles themselves but we also need to reduce the need to travel – and to shift people onto the modes that are lowest carbon of all walking and cycling, and to a lesser extent public transport.

This probably leads to the conclusion that a carbon policy on transport comes in two waves. The first wave is based on ’smarter choices’ which focuses on reducing the need to travel (through planning and taxation policies) and on encouraging people to use lower carbon modes – in particular walking and cycling (through better information on modal choice, pricing policies, road-space re-allocation, better provision for walking and cycling and planning policies). This is the first wave because much of this can be done relatively quickly as it doesn’t require emerging technologies. Much of the capital investment required is also relatively modest – the main focus is on current expenditure.

The second wave is vehicle technology – as this requires a longer timescale. For example much of it follows on from a shift in the energy generation mix. So plug-in cars or hydrogen cell buses only really become low carbon when the national grid upon which they rely has been de-carbonised.

It’s a practical challenge then. And if the fatalists are right and we’re all doomed anyway – then at least we gave it our best shot.

Jonathan Bray