London’s Congestion Scheme, never the most successful or logical transport policy, looks like it is about to descend into outright farce. Transport for London has just opened a ‘consultation’ which is looking at ending the exemption for low-CO2 vehicles. Today, if your vehicle has a CO2 rating of below 100g/km, you don’t have to pay the daily £10 fee to drive into central London.

Come July, that exemption will almost certainly be lowered to just 75g/km CO2, which means that only pure-electric vehicles will now be exempt. If you’ve currently got an exempt vehicle, you’ll get a couple of year’s grace, before the exemption for existing sub-100g/km cars is pulled in July 2015.

According to a report in the London Evening Standard, around 2,500 of the 70,000 vehicles that currently enter the Charging zone each day are exempt. TFL are said to be ‘concerned’ that the current set-up creates an ‘incentive’ for hybrid and diesel cars to enter the zone. There are even claims that there could be 6000 ‘free’ cars entering the zone by the end of 2013. Other money-raising changes in the consultation include upping the non-payment fine to £130 and closing some of the C-Charge payment points in shops and petrol stations.

All of which looks like plain old ‘revenue protection’ for a scheme which was always primarily about making money. The eco-cover for these moves is said to be an attempt to reduce the number of diesel cars in the zone, because they emitted up to ‘22 times more particulates’ than petrol cars. All of which would be funny, if it wasn’t farcical.

After all, central London, like many UK cities, has massive particulate and NoX problems, caused almost entirely by lumbering, stop-start, buses and commercial vehicles. In London, the ageing taxi cab fleet is said to be responsible for 25 per cent of these diesel pollutants. Removing the charge exemption from a couple of thousand brand new diesel cars with the cleanest Euro V engines - which also probably spend less than an hour on the move in the zone - is absurd. Doing the same to petrol hybrids - the lowest polluting vehicles after those powered by gas - is idiotic.

Despite searching the TFL website, I cannot find a detailed annual summary of the C-Charge’s financial performance in 2012 - this first full year since the Western Extension was brought to an end. However, it made a profit of £136.8m profit in 2012, after the £90m it costs to run the tolling system. What we can’t work out is how much of the £226m total income is raised from fines. In 2008,  though, a massive £73m of the income was from late-payment fines.

Perhaps, one day, TFL will decide what the C-Charge is supposed to be. The original idea that it would enable quicker, more reliable journeys was killed off years ago with TFL’s programme of road space removal. Official figures showed journey times were no better three years after the C-Charge was introduced. 

If it is intended to reduce the number of vehicles in central London to a minimum, then TFL should expect rapidly falling profits. But any attempt to re-spin it as method of improving air-quality - when London has one of the most polluting surface public transport systems in Europe - should be laughed out of court.