@AC with the golf, Richard Porter, Matthew.. others have already said but I would think the £25 charge is for 2001 and older vehicles WITH >=3.0L engine, not all 2001 and older vehicles.
@Andrew Heenan, "The 15 persons per bus is either fiction (in zones 1-3, anyway), or it's a 24 hour, all of greater London figure. Either way, it's *dishonest* to quote such an irrelevant statistic, when we both know that zone buses are packed to the gills in the peak."
Not dishonest at all; the bus will pollute full or empty (one question is how much the pollution level varies based on load...) so you can't just claim the bus is efficent full, end of disucssion, if the bus is not full most of the time.
I must comment, the city I live in has this type of situation. The buses USED to have signs on them that said something like "if it weren't for this bus you'd be behind *30* cars". They had to take them down... the buses on the University campus run full, the other ones even during rush hour will run with like 15 people in them, and I've seen them go by with literally 1-2 people in them (well, 2-3 if you can't the bus driver). It turns out 15 people can't drive 30 cars 8-).
Living in the states, this won't apply to you but I have 2 comments I wish would happen here:
1) Better public transport. Locally we have buses and taxis. The buses on the university campus are great, they run at 15 minute intervals and run quite full. The ones off campus.. 1 hour intervals, and per the above they run virtually empty. IMHO they should have smaller buses that can run more frequently. I wouldn't ride the bus knowing I could be stranded for 1 hour if I miss it (it takes maybe 20 minutes to drive across town here.) 15 or even 30 minutes? I could deal with that.
2) Better cars. I drive a 2000 Buick Regal with a 3.8L V6 right now. (See my note on gallons below*) This car gets about 22MPG city and 36MPG highway (but I got over 40MPG on a recent long trip). My parent's 2000 Deville gets 24 city and 36 highway, with a 4.6L V8. If I get something like a US-spec Honda Civic (with the 4-cylinder, not V6..) it is supposed to get 30MPG city and 43.2 highway. Higher mileage, but not much higher considering the Civic is smaller, and slower (MUCH slower compared to the V8 Caddy I bet).
The US-Spec cars, the big engines are carefully tuned to try to maximize gas mileage (not so much on SUVs but certainly on cars); small economical engines, they'll drop it in then decide "Ohhh, it needs more power for US use!", change the gearing to power gearing and tune it for power. Result? Why bother. The car still doesn't have the power it would with some bigger engine, while getting almost as low gas mileage.
One of the few smart things Bush's administration has done was to pass the new fuel economy requirements here upping the CAFE (corporate average fuel economy) from a pathetic 20MPG to 35MPG (in British gallons this goes from 24MPG to 42MPG). I'm a libertarian so I hate regulation**, but the car companies left to their own devices are doing the bare minimum -- most are right at 20.1MPG average (for *cars* -- SUVs are counted separately) and just aren't giving a lot of choices of fuel efficeint vehicles. Some technology will come out that is supposed to increase mileage 10 or 15% -- it does on European-spec cars.. the US model comes out "Oh, hey we increased power 10-15% with the same mileage as the previous model year!" Blah. Now they are finally scrambling to apply this to provide good mileage.
*Side note. 1 imperial gallon (as used in Britain) is 1.2 US gallons. This is partially why US MPG figures look so bad.. mainly it's because they are bad though. I converted the above numbers to imperial MPG so they'd compare with what others have posted.
**And also have no one to vote for. The 2-party system here is broken.. if you wonder about the low voter turn out here, that is why.. democrats and republicans don't represent most people here.