By the time you've finished reading this, you may as well have just got out and walked anyway

It looks from the news as though there's going to be a set of pilot schemes set up in the near future, in order to test the viability of by-the-mile road pricing. This is a plan that has been controversial to say the very least - lots of people seem to be regarding it as little more than a thinly-veiled attempt to wring more money out of motorists, and it inspired an enormous petition to Downing Street back in February. As it happens, I did sign that petition, and I did get an email from Mr Blair (or "me mate Tony", as I think I should refer to him - after all, he did email me...)

The weird thing is that today's news story, although it does mention the vast opposition to the road pricing plan, doesn't make much mention of the petition's first objection to the plan, which was that road pricing would involve satellite tracking of every single car so that the system could tell which roads they'd been on. That was definitely my main objection to it, and it looks like it was much the same for many others, but now it seems that the opposition to road pricing is being characterised by people who simply don't like the idea of paying more to drive.

I may as well put my cards on the table immediately as regards this issue - driving around is, regardless of what motorists will tell you, a dangerous, noisy and polluting activity. Within, the UK, 3,201 people died in road accidents in 2005, of whom only 52% were in a car at the time. To put that in perspective, it's an average of over 8 people per day, or one every 3 hours. Cars are responsible for 15% of CO₂ emissions within the EU, and car ownership has been steadily increasing throughout the '90s to the point where there are nearly 500 cars per 1000 people. Unless things change, and soon, the roads are going to become even more congested and dangerous - and making driving cost more, provided that money goes back into developing public transport, is a good, market-led way of trying to avoid that.

(I'm aware that there are people for whom driving is the only option - those living right out in the sticks, or little old ladies without any other way of getting around. I'm also aware that it is not impossible to work out discounts and exemptions for special cases. It worked with the London congestion charge.)

Anyway, if it's a good idea to raise the cost of driving, why is it a bad idea to introduce road pricing? After all, surely that's a fairer way of doing it than simply using road tax - it means that those who don't drive much don't have to pay so much. And indeed, I would be fully in favour of road pricing schemes, if only it weren't for the extremely Orwellian concept of every car being satellite-tracked everywhere it goes. This is an incredibly bad idea on pretty much every level. First, the practicalities would be difficult. Would the car be allowed to move unless the tracking box had a satellite fix? Given that GPS units frequently take a minute to get going, or more in difficult terrain, immobilisation this will frustrate drivers who aren't used to having to boot up their cars. How about people who use an underground car park, making it impossible to get a satellite fix? The alternative is to let the car move without the tracker working - but how far? Would it suddenly die half way down the street if it wasn't sure where it was? More to the point, having a critical piece of kit being run by a computer is never a particularly good idea, and there's no such thing as a mechanical backup for a GPS system. (Unless you're planning on having a bloke with an Ordnance Survey map and a megaphone following everyone around.)

The cost is another issue. Satellite technology has got a lot cheaper recently, but a decent consumer-level navigation unit will still cost you over £100. And fitting these to what must be getting close to 30 million vehicles would not come cheap. What's more, the GPS system itself is not cheap to maintain ($750m per year, according to Wikipedia), so what's to stop the US military from charging as much as it likes, once this enormous and guaranteed market opens up?

By far the most important problem with a satellite tracking system, though, is that too much information is generated. In order for the Department for Transport to successfully charge everyone for their road usage, it will need to know which roads people have been on, and when. The implications for this - that the government instantly knows exactly where all of its citizens are (assuming that they drive), and where they have been for goodness knows how long - is simply terrifying. I've heard the argument advanced that this isn't a problem, because those who haven't been engaging in illegal activity have nothing to fear. However, even if you do trust the current government not to do horrible things with this information (for the record, I actually probably do), that's not the question that you should be asking. What you should ask is, "Do I trust the next government with this information? What about the one after that? And the next?" Imagine a situation where a future government, after, say, a major terrorist incident, decides that it needs to seriously clamp down on possible dissent. Do you want them to be able to look up in their database and find out that you drove to a "Troops Out Of Iraq" demonstration 15 years previously? As you can see, there are some very good reasons not to make this kind of information available.

How, then, might a road pricing scheme work without this kind of threat? There's one very simple solution: make the data flow the other way. That's pretty much all you need to change. If, instead of information flowing from the cars to the system, the system told the car what it had just gone past, then privacy problems disappear. How would this work in practice? Well, consider what would happen if every car was fitted with a low-power radio transceiver, with a maximum range of about 20m. The technology for these is already pretty much commonplace, and therefore cheap, and it wouldn't be difficult to fit them all if it became part of the MOT to have one installed. Radio beacons could then be fitted along the nation's roads - for example, every time a speed limit sign was replaced or maintained, a beacon could be added to it. These beacons would broadcast a code for the appropriate type of road; then, whenever a car passed one, the onboard transceiver could record the road type and add an appropriate charge to a running total. At no point would data have to flow to the beacons.

Paying one's charge would likewise be fairly easy to do - if every Post Office, or better yet every petrol station, was equipped with its own transceiver then it would be trivial to make the car's onboard transceiver transmit a unique code, perhaps based on the car's numberplate and current date and time, and the total to be paid whenever a button was pressed. Paying this at the petrol station would authorise a similar code to be broadcast to the car to reset the total; instead of using an immobiliser, it could also be a requirement of the MOT to pay one's total. Notice that no information about where the car has been is ever sent to the central system, only the amount paid.

As you can probably tell, I've put rather more thought into this than is strictly necessary. I do think, though, that with the encroaching invasions of privacy in this culture, it is very much worth looking into alternative ways of dealing with problems that minimise concerns from the outset. The bottom line is that we all need to drive less - if we can manage to do that without Gordon Brown watching our every move, I'd be much happier.