The London congestion charge is beginning to look like a Greek tax - no-one actually pays it.
There are existing exemptions for black cabs, registered private hire vehicles, motorcycles, emergency services and some NHS vehicles.
Blue badge holders also are eligible to register for a 100 per cent discount, even if they don't own a vehicle or drive."You can register up to two vehicles that you would normally use to travel within the charging zone. This could be your own vehicle, or one you travel in." No scope for abuse there, then.
There are also exemptions for electric, hybrid and alternative-fuel vehicles, like this Lexus RX450H SUV, or this Porsche Cayenne hybrid (emissions 193g CO2/km).
From January 2011, Boris has created a new Greener Vehicle Discount, providing a 100 per cent discount to cars that emit 100g/km of CO2 or less and meet the Euro 5 standard.
Trouble is, rather a lot of cars meet this standard - 25 different models, according to the Government's VED database. Don't think you'd be driving an expensive or compromised eco-special - you could choose a Volvo S40 'DRIVe', a Mini Cooper D, a Ford Focus 1.6TDCi 'ECO start-stop', a VW Golf 1.6TDi 'Bluemotion', a Fiat 500 'TwinAir' or many other affordable mainstream cars.
It is difficult to see how these new exemptions will make congestion or air pollution any better. Some might see it as a little unfair that the least green form of transport is becoming cheaper just as public transport fares are rising.
Perhaps the most serious problem this will create is that a greater and greater proportion of vehicles will become exempt over time. Having created an exemption, it will be politically difficult to take it away. It could be argued that with this move, Boris just abolished the congestion charge.