London Congestion Charge improved?

Ken Livingston, the Mayor of London, has announced changes to the so-called "congestion charge" for central london:

London Congestion Charge becomes CO2 tax | The Register

This has been a very confused programme. It certainly has not prevented congestion in the City of London where I live and work, and many people think the charge is just a ruse to raise more tax.

I'm comfortable with the idea of a charge to reduce the impact of traffic on the City, and this new change seems to be an improvement. We will see.

... but I would prefer to see a scheme where the overall polution impact of a vehicle was assessed in terms of:

• Air pollution (which is what this new change does)
• Sound pollution (Harleys pay more than BMWs)
• Size (Hummers pay more than Minis)

The new CO2 based system must have some way of working out what charge applies to each vehicle, perhaps by make & model, and this same catalogue could hold size and noise data.

Lastly, the scale should be sliding. By that I mean that over time the tolerance for air pollution, noise and large vehicles should be reduced.

But Ken's CO2 move is a step in the right direction, I think.