Can anybody explain to me how are we going to dispose/recycle/throw away HUGE batteries like the ones used by Prius? Can anybody suggest how to fit a family with 3 children and double buggy in a Prius. Please answer,I would love to be greener.

Ivana, London,

Andy and Nic, good idea but unfortunately you are both wrong. We have already seen the damage that higher fuel prices have, just look at the difference in your food bill. The solutiuon to congestion is two fold. For motorways, initially lorries should only be allowed to use the inside lane and should not be allowed to overtake. When overtaking on a busy motorway at 50 mph all the other cars are bottlenecked into the outside lane causing additional congestion. There should also be moves to move more freight off the road and put it on trains. In busy city centres its simple. Ban private vehicles and make public transport cheaper. Its simple economics, no car = high demand for transport. Low price = high demand for transport. What should be concering the 'Green' camp is that the government are not intrested in saving the planet, just making money out of us.

Grant, London,

An alternative explanation (although it won't explain it all) of the drop in sales of the highest-CO2 cars is that manufacturers have managed to push models below the threshold - eg, BMW 5-series sold since March 2007 have dramatically lower CO2 emissions than earlier models.

Tony Scales has an excellent point - the raising of taxes on cars has far more to do with the government being able to get away with raising more tax by doing this. If that wasn't the case, and CO2 really was the motivation, fuel for aviation, domestic and commercial uses would all be taxed in the same way. I have thought for some time that the Agas should be as politically unacceptable as 4x4's!

Tim, Preston,

I am in favour of overall CO2 emissions limits for cars, but can at least one of the many government/academic experts on climate change explain why cars have a 250% tax on carbon (via fuel duty and full VAT) whilst home energy, which emits roughly as much CO2 as cars in the UK, has a 5% tax via reduced VAT?

tony scales, watford, england

David Leslie and others: if you need a big vehicle for your holiday, hire one! What's the use of driving a bus all year if you don't need it?

Tina Rhea, Greenbelt, Maryland US

None of the cars listed will take me, my family (including dogs) and caravan. Therefore, to have a family holiday I've got to either go B&B, which I can't afford, or fly abroad, thereby increasing my carbon footprint. I would imagine that a lot of the 'new' car sales are for thos epeople that already have a larger car, which they will keep for longer to avoid the tax hike.

David Leslie, Perth, Scotland

Nic has it absolutely right. The best way to reduce car use and encourage efficiency (thereby reducing emissions) is to increase the MARGINAL cost of car usage...ie fuel cost. This is why a consistent carbon tax needs to be implemented globally, outside the control of politicians. Increasing the cost of the car will not have the same overall effect...but it does play to the politics of envy and makes for good soundbites.

The only reason why we have the interest in hybrids and fuel efficiency in the first place (and investment by car manufacturers) is the increasing price of oil...nothing to do with public perceptions of global warming or concerns about 'saving the planet'.

Andy, London, UK

I find it ridiculous how much focus there is on fuel emissions of vehicles when the waste produced in the manufacture of the vehicles is completely ignored. An average car produces 2,600kg of solid waste in its manufacture, 130kg of which are highly toxic. On average, one million litres of water total will also be polluted during manufacture, as well as 1/3 of the gaseous emissions that the car will produce once it is on the road. Yet car manufacturers still design cars to last for a total of ten years (when they could be built to last much longer with regular overhauls) while at the same time trying to constantly reduce post-manufacture emissions because this is the only waste that the public is aware of. You hear people say "my new car is much more environmentally friendly than my old car" - this makes no sense, the making of your new car has caused more pollution that your old one could have, no matter what the emissions from it.

D Welch, Manchester, UK

We all know this global boring stuff is about taxing us more to raise cash for pet projects, New Labour love it and fail every time to reduce their footprint! Look at any government office after 5pm and the lights are burning bright despite the desks being empty. we also know green electricity is nowhere near as green as made out, behind every plug in car is a coal power station? People should be able to drive whatever cars they like, put the tax on the fuel like you have done now and let the users define how much they pay up front taxes on cars makes a joke of green taxes! Also green cars need to be redefined as to their whole of life cost, ie a Range Rover will last 20yrs where as a Prius needs replaing in 7yrs so the build of the car takes energy and CO2 so these things need to be factored into the 'green' of the car, also mosr Rang rovers do a lot less miles than the rep screeming up and down the motorways in his BMW so again the fuel tax looks easiest and fair way to pay!

Richard de Gerber, Kingston upon Thames, UK

Slapping a blanket road tax on a gaz guzzler misses the point entirely, it is simply a jealous response ny unreformed socialist to rich people spending money. A city trader with a Ferrari who drives it occasionally on weekends, has far less impact on the environment thana salesperson doing 2000 miles a week in a Ford Focus. The only fair way to tax impact of driving on the environment is to have a tax on fuel, the more the car uses (combination of efficiency and distance driven), the more you pay in tax. Simple and fair, but then since when have 'green' campaigners been interested in that, much easier to attack the rich.

Nic, London,

There's no such thing as a "green" car. They all need to be parked - think of all the land that takes up and the mess it makes of suburban streets - and they all contribute to congestion and the risk of accidents. Non-green cars are still delayed in the congestion, giving off fumes noxious to health and the environment. The congestion delays buses and makes them unreliable, giving people an extra excuse to stick with their cars.

The only cars which could perhaps be called "green" are those belonging to car clubs. Being more intensively used, they spend less time parked; and they are far more likely to be used only for essential trips.

Barry, Wallington, UK

Apart from cars such as the Prius being about 25% more expensive than the equivalent petrol version, the benefits as far as fuel and thus CO2 savings are concerned are only in cities in heavy traffic. The savings on such cars are also negated considerably as the batteries have to be disposed of when they are finished.

A diesel engined car to Euro 4 specifications and an engine such as the new Focus with less that 120 Gr/Km, will return 50 to 60 mpg or more with normal driving. My 2001 Focus diesel with currently at 136 000 km has a Gr/Km of 153 as tested recently, and overall it has averaged 47 mpg without any special economy driving.

But the real answer is going to be hydrogen once the government makes the decision to build enough nuclear power stations to make the manufacture feasible. Britain is way behind France where there are 56 which supply 70% of France's electrical needs at this time.

B J Deller, Marbella, Spain