Congestion charge loopholes: Now just learn the Knowlege...

You don't have to buy a Prius to avoid Ken's 8-a-day fine. Keith Adams looks at unusual options

How desperate are you to avoid London mayor Ken Livingstone's congestion charge or any of the other, similar systems that are set to spread into the provinces in the near future? Alternative-fuel cars and disabled drivers already get a 100 per cent discount, as do motorcycles, recovery vehicles and the Queen's official Bentley limousine, which doesn't run with number plates.

Without resorting to driving a milk float or getting a job as an AA man, there are a number of ways to exploit the loopholes in this system as a private, law-abiding motorist if you are willing to be a little inventive. With tongue firmly and sometimes not-so-firmly in cheek, you might like to consider the following:

1. Drive a Public Service Vehicle

Ambulances, fire engines and other emergency vehicles are exempt. Some don't pay road tax, either, and remain registered as public service vehicles (PSVs) even when no longer in active service as long as you don't convert them for another purpose. If it says PSV on the V5 registration document, then it's still a public service vehicle and you can drive it on an ordinary licence. So you could buy an old ambulance or even a Green Goddess (not very "green" with a four litre-capacity petrol engine) and avoid the charge. Specialist auction houses such as Merthyr Motor Auctions, in Wales, have ambulance sales and not all of the lots are hulking great Mercedes Sprinters. For around 2,000, you can buy a "rapid response" ambulance based on a Renault Scnic MPV. Even if not officially in use, an ambulance retains its status as long as it says "ambulance" on the outside and is carrying oxygen.

2. Drive a 'Minibus'

Minibuses registered with Transport for London (TfL) don't pay the charge, either. Anything between nine and 17 seats (including the driver's seat) is a minibus or can be registered as such or as a public service vehicle. This could include a nine-seater, 110in-wheelbase Land Rover Defender, so you don't have to drive anything as un-cool as a Transit crew bus to save your 8. You must be 21 to drive a minibus, but as long as you acquired your licence before January 1997 and you are not driving it for "hire or reward" you don't need a special licence.

3. Drive a 'Minicab'

Hackney Carriages licensed black cabs are automatically exempt from the congestion charge, but this would entail doing the Knowledge and becoming a proper cabbie. Hand over 75 and a valid MoT and you can register your car as a congestion-charge exempt minicab. Because TfL offers no physical parameters as to what constitutes a minicab, this has been open to free interpretation: 17 Bentley Continentals, three Maybachs, eight Rolls-Royce Phantoms and even a two-seater Mercedes SL are among the unlikely cars registered as minicabs with TfL. Their owners are presumably trying to anticipate the 25 Band G charge that comes in this coming October, but TfL says it will contact owners of the suspect cars and demand to see records of their trading activities.

4. Drive a foreign- registered car

Foreign-registered vehicles are not exempt, but it is difficult for TfL to recover the charge. Some embassies in London refuse to pay the charge on their diplomatic cars because they regard it as a tax; the American Embassy is thought to owe 1.6m in unpaid fines. You may drive a car in the UK on foreign plates, as long as it is insured, for up to six months longer if you can prove you have used the vehicle outside the UK before it has to be registered in this country.

Motorcycles, mopeds, scooters

Motorbikes, motorbikes with sidecars, mopeds and bicycles are all fully exempt. They do not have to be registered. Motorbikes that exceed one metre in width or two metres in length are not exempt.

To authorise your vehicle as within the size constraints, you must take it to the vehicle storage pound, along with your V5C.

Three-wheeled tricycles are not exempt and will have to pay the charge.