Once again 'road pricing' is being discussed as a solution to traffic congestion.

The system proposed appears to work as follows:

Each vehicle has a box that receives position signals from satellites (the 'downlink') (GPS or the European Gallileo system) and records vehicle movements in some sort of local memory. At some specified interval the box sends a burst of this data (possibly by cellular telephone or by dedicated new network)  (the 'uplink') to the official road pricing computers that then generate a monthly bill for vehicle usage. The box must be programmed to identify the individual vehicle.

But the entire thinking is far from adequate. Some obvious and serious problems emerge after a little critical thinking.

Their claims of future gridlock are entirely false. Just ask yourself - it there was gridlock outside your door, would you choose to travel by road? If it took four hours to drive to work (and four hours to drive home again) what would you do? Change your job? Move? One thing's for sure, you wouldn't accept the four hour journey to work, and neither would anyone else. If there's no one sitting in the gridlock, then there's no gridlock.

London traffic has been self regulating for at least 30 years - the growth in London traffic has been far smaller than the growth in national traffic. Similar effects are present in other big cities.

When planning a journey the first question you ask is: "Have I got time to make the journey?" If there's much in the way of congestion, then this will strongly influence you travel decision. Think about a trip to the shops. It's 4:30pm and you have 60 minutes before the shops shut. You don't travel to the next town (although the shops are better) because you don't have time to travel.

If travel is constrained by the time it takes, then clearly congestion will always self limit depending on the level of congestion that people are prepared to accept. If congestion rises above acceptable levels then people will always find alternatives.

But the big picture is far worse even than this. For every cost constrained road user there are probably 10 time constrained road users. We'll price the less wealthy off the road, only to later discover that someone who was previously prevented from travelling due to delay has taken his place.

If you doubt this argument, consider very carefully the forces that have driven the development and obvious success of out-of-town retail parks and business parks. They are fundamentally a market response to town centre congestion. The market recognises that people and businesses need an alternative - no one wants to sit in congestion - provide an alternative and people are only too pleased to accept the offer.

This self regulation takes place on various time scales. People and businesses have moved away from cities to avoid congestion. People normally consider the time taken to travel to work when deciding where to live and were to work. The bottom line is that no one likes to be stuck in traffic, so they take steps to avoid being stuck in traffic. It isn't always effective of course, but it is effective enough to enable efficient economic activity and it always will be.

They have recently suggested that traffic congestion represents a cost to business of £20 billion pounds per annum. The principle here is that time is money. Delay costs money because people can't get as much done in a day. So far so good.

But one of the primary functions of business is to control costs. Clearly the road pricing advocates know this because they expect business to seek alternatives to travelling at congested times or in congested places.

So why don't they make the obvious connection between the costs to business of congestion and the costs to business of road pricing? Road pricing simply adds a pointless layer of administration to encourage businesses to spend less in the same way they they wish to spend less on time wasted to congestion already.

Since time is money, the costs of congestion already represent a road pricing, congestion charging scheme. The claimed £20 billion lost to congestion is already effective road pricing to business. It either works or it doesn't and the proof exists.

In truth it's already working well. Businesses with travel needs have already located out of city centres onto industrial estates and business parks with good road connections. We simply don't need another layer of administration.

This 'time is money' point describes one of the fundamental mechanisms of congestion self regulation. It is worthy as a separate point because 'time is money' is a cause while self regulation is an effect. There's very little sign that the government have even considered either point.

How are we supposed to avoid high charges under roads pricing if we don't know what the charges are? Signs by the roadside might pre warn of high charges ahead, but massive costs would be involved and we'd lose the chance to prevent a journey - the journey would have started before the charge was known.

Some people might use the Internet to find the current charges on a planned rote in advance of travel, but what percentage of travellers would bother? 1 in 25? Most of us wouldn't know the charge until the bill arrives at the end of the month. And most people will just pay the bill without investigating exactly where and when the highest charges were incurred.

It's been suggested that charge predicting technology will be available to everyone via satellite navigation equipment integrated with the road pricing apparatus. That may well be the case when planning a route, but the same quality of information won't be available when deciding where to live or when deciding if you have time for a trip to the shops. Once you're in the car the chance of deciding not to travel is enormously reduced.

The part of the system in individual vehicles will be extremely vulnerable to tampering, fraud, induced failures, disconnections and otherwise being disabled, defeated or circumvented.

Satellite signals are weak because of the distance to the satellites. This means that a tin foil hat over the aerial will be enough to prevent reception of the position signal. Whatever safeguards are put in place, people will find a way to defeat the system. It might be suggested that if signals were not being recorded a vehicle should be disabled, but there will always be areas of bad signal and obviously we can't have underground car parks filling up with disabled vehicles.

The need to deal with technical problems (for example breakdowns in the in-car system) will greatly facilitate fraud and abuse.

Here are the principal technical and practical vulnerabilities:

• jamming the downlink (tin foil over the aerial, dressmakers pin through the aerial cable, local jamming signal generated from very cheap equipment)
• jamming the uplink
• erasing the journey memory before the uplink
• breaking the in-car unit (details will be published about how to create subtle but effective breakdowns leading to unmanageable warranty claims)
• disposing of the in-car unit
• removing the fuse for the in car unit (replace with blown fuse for best effect!)
• uplinking false data (the more the better)
• false vehicle identification data (reprogram the box?)
• false billing data (your bill goes to someone else, the entire vehicle registration process is further threatened.)
• flat denials of responsibility (I wasn''t there - I'm not paying - You prove I was).
• not paying the bill (and keeping out of sight)

Good taxes take more from people who can afford more, but road pricing will tend to charge everyone the same for road use. The low paid catering worker or health worker will pay the same as the rich business executive. The rich executive can travel as he wishes, yet the low paid worker will have to consider every journey with care and may not be able to afford to travel to work.

High charge places will only be visited by rich people - the poor would be excluded.

The system would be extraordinarily expensive. These finds will be taken out of society by some method. We have around 32 million vehicles. Even at £100 per vehicle we're already spending 3.2 billion, and with new vehicle sales running at about 2.5 million per year the new units will add up to £250 million per year alone.

Then there's the development costs, especially of the official management system and the infrastructure.

Then there's the operating costs, many many thousands of employees would be needed for day to day administration.

Then there's debt collection - with at least 25 million road users incurring regular bills, and 10% of them not paying we've got 2.5 million * 12 months = 30 million unpaid bills per year. How many staff are going to be needed to deal with this and what will it cost?

The proposals raise many issues of civil liberties and privacy. Computers will record our every journey. The bill will contain details of where we've been (and if it didn't we couldn't manage our charges). So what happens if we have an affair and our wife reads the bill? These are just the tip of the iceberg of the privacy issues raised.

What would happen if you got a bill for driving on a road when you weren't there? Obviously it will happen. We can imagine all manner of phone calls where the call centre flatly denies that their system makes mistakes. Billing errors would become a real nightmare for some responsible members of society.

And what happens with wide area breakdowns? We'd better pray that a system failure doesn't lead to vehicles being disabled. Imagine the chaos if all vehicles in London stopped. Imagine the danger if some vehicles on a busy motorway just suddenly stopped.

And what happens when the system in you car breaks down? Will you rush to get it repaired? Will you be committing an offence? Will you want it to break down? Will you make it break down? And who could afford to do warranty repairs on equipment when many skilled people wish that the thing would break down?

Internet sites will appear explaining exactly what's needed to make the in car unit fail. 

Motorways can certainly become congested and would attract high charges. But motorways are safe roads. If we did manage to divert traffic to other roads more people would die because they would be driving on less safe routes. This may lead to high charges being extended to alternative routes, but some alternatives won't be just a different route to the original destination. Some alternatives will be to entirely different destinations. (For example shopping in a different town).

Perhaps we could consider basing the charges on the relative dangers of different roads with greater charges applied to more dangerous roads? But doing this would favour motorway travel and encourage motorway congestion...

Assuming that the doomsayers are correct and Anthropogenic global warming is real, and that we need to tax carbon emissions then any move away from fuel duty will not be of benefit to the climate.

Many non technical people fail to appreciate that virtually every single carbon atom in motor fuel ends up as atmospheric carbon dioxide when the fuel is used. This means that fuel duty is a perfect carbon tax that precisely charges for each and every carbon dioxide molecule emitted. Any change to road pricing will move away from this ideal. One example might be to choose a slightly longer route that uses more fuel, but which is cheaper because busy places are avoided.

Someone will have to pay a road pricing bill for the use of a specific vehicle. Who will that be? The owner? The driver? Will owners have to pay for usage of a vehicle entirely outside of their control? Will owners have to 'name the driver' with a whole extra layer of disputes and administration difficulties? The problem here is that each alternative has problems.

Perhaps they will expect us to poke our national identity card into a dashboard slot before we start driving?

If they ever do decide to fit boxes to all vehicles, we should be extremely aware that the boxes will be used for all manner of other functions. Examples include:

• Remote disablement of the vehicle. (Great when the Police want to stop your stolen car, terrible when sophisticated thieves want to steal your car).
• Intelligent Speed Adaptation (preventing your vehicle from exceeding a speed limit). It's very bad for road safety to take control and responsibility away from drivers.
• Automatic fines for speeding or other offences. (Clearly the box could record speeding offences and send you a fine in the post).
• Tracking stolen vehicles?

Areas of bad reception

How will the system cope with areas of bad reception of the satellite downlink signal? Tunnels and underground car parks are obvious, but there will be reception problems in crowded city streets too with tall buildings either side.

Foreign vehicles

What will happen with foreign vehicles? Will they pay and if so how? Will French folk visit the UK to fill up and get fuel duty free?

Private land

Will the system stop charging when vehicle move onto private land?

Charge disputes

How will they cope with huge numbers of legitimate disputes regarding incorrect charges? What evidence will be available to either party in the dispute? Do you fancy have to prove to the road pricing authority that you weren't there?

Debt recovery

All these monthly bills will lead to massive debt recovery issues, especially if people are unhappy about the system or the charges.

A massive information technology system

This would be around the biggest IT project undertaken by Government. And we know their track record with big IT projects. It doesn't work on time. It goes way way over budget, and problems persist for years after the (delayed) launch.

Circumstantial evidence

Suppose there's a bank robbery. All the vehicles in the area are checked and one happens to belong to a former bank robber. Is he guilty? We don't know, but the huge amount of data will give rise to many remarkable but nevertheless random coincidences. A great deal of false circumstantial evidence would be generated.

Short term benefits, long term costs

If by some freak chance road pricing did deliver a substantial benefit in a particular place at the time of introduction, that benefit would be short lived while 'traffic sorts itself out'. After a year or two, the traffic will return to normal and the overhead costs will live on.

Non driving vehicle movements

What if your vehicle is on a trailer or is being towed? Will it still incur a charge? If it doesn't incur a charge, then we have a mechanism whereby people might be able to defraud the system by telling it that the vehicle is not travelling under its own scheme.

We live in a free market society. This works because people make free choices within their own interests and also within socially acceptable constraints. Free choice in transport is of fundamental importance, and works well in the common interest because of the competing and balancing needs of a great many individuals. Congestion is a fundamental regulator of itself because if it's too busy to be acceptable we choose not to travel.

The job of government should be to facilitate free choice. In transport issues this means providing roads and public transport services to suit public demand. In many congested places, we are suffering because the government has fallen behind in its duty to provide suitable roads. In many city centres, congestion is considerably worsened by 'traffic calming', loss of road space, loss of parking spaces and aggressive anti car policies.

The ideas that 'every time you build a new road it fills up with traffic' and 'you can't build your way out of congestion' are both very fundamentally false. Roads only fill up with traffic when there's a demand, and they only actually 'fill' when the road is unsuitable for the demand. (If you doubt this, imagine building a three lane motorway across the north coast of Scotland - there simply isn't any demand to fill up such a road, and there will not be within the foreseeable future.) In some city centres it really is true that you can't build your way out of congestion. In these situations there are historic narrow streets and important buildings that cannot and should not be demolished. The answers here involve public transport provision and efficient and optimal traffic management.

We have proved over the last decade or so that we can't 'force people out of their cars'. Deputy Prime Minister, John Prescott said famously in 1997: “I will have failed if in 5 years time there are not fewer journeys made by car.” History proves him a failure, and traffic growth has continued precisely at its long term trend level of +8.75 billion vehicle kilometres per annum.

So these are the sensible measures required to tackle congestion:

• Stop causing congestion with anti car policies.
• Manage traffic for genuine transport efficiency, not for political ideology 
• Continue to build and develop the strategic road network.
• Make adequate investments in road infrastructure from the massive road use tax take.
• Provide clean, cheap and efficient public transport alternatives. 
• Encourage and facilitate a reduction in travel needs by promoting technology that supports home working and home shopping.

Firstly let's be quite clear that some modern traffic congestion is artificially created. Loss of road space to bus lanes, traffic calming and road narrowing schemes. Excessively low speed limits. Traffic light phasing that favours pedestrians or buses unnecessarily. Loss of town centre parking, leading to lots of extra traffic simply looking for somewhere to park. So the first solution to congestion is proper traffic management - proper traffic management will be free from political ideology. Instead proper traffic management must always be driven by efficiency and safety. The idea of promoting 'modal shift' has already failed. National traffic growth continues at precisely the level established in the 1950s. (see the graph on this page)

Road pricing is entirely doomed to fail. It would be an extraordinary misuse of public money because it can never work in practice, nor can it deliver the benefits claimed.

But there is one real benefit from these road pricing proposals. They are a timely warning about the huge gulf between the DfT and reality. We must pay very careful attention to this dangerous and worrying problem.