I want to walk my son to school, really I do. The journey is not that far, we could do it, but we're late. And we're tired. And it's raining. And how much can a mile - OK, half a mile - in a car hurt the planet, really? Jasmine Abdal goes through none of this mental wrangling in the morning. She just gives her 13-year-old daughter Prerna the once-over - hair, uniform, PE kit - and sees her out of the door and across the road to the bus stop. At five past eight a big yellow bus comes wheezing down the road like something out of The Simpsons or Spiderman or a thousand movies. But this is not America, it is quiet, suburban Surrey, just beyond the M25 and under the flight path for Heathrow.
"Prerna never misses the bus," says Jasmine. "I make sure of that. Once she is on board I know she will get to school safely."
The custard-yellow bus is a bright and bold sign that Something Is Being Done For The Kids. That may be why David Cameron is so keen on it. Last week the Tory leader test drove eco-cars on an airfield not far from Prerna's home and cited the buses of Runnymede as evidence that "where people have voted blue, their councils have gone green". There will be much more of this under Tory rule, he promised. But hang on, we have been here before. Often.
"If these yellow buses are good enough for American children, why shouldn't our children have them, too?" asked John Prescott five years ago. The Deputy Prime Minister started talking them up after Labour came to power in 1997, but it was not until 2001 that he launched a series of pilot schemes. "If it's a big success we will certainly consider making it a requirement of all local authorities across the country."
So where are they? Five years after being heralded as the future, there are still only around 100, serving 6,000 children. You wait ages for a bus and then none come along at once, although they have never been more needed. The price of petrol has soared to almost £5 a gallon, but then so has the popularity of the gas-guzzling 4x4s, now one in eight of all cars on the road.
The number of children being driven to school in cars has doubled over the past two decades (40 per cent of primary school pupils are driven, 18 per cent of secondary students). A billion trips are made on the school run every year and, between us, parents produce two million extra tons of the greenhouse gas carbon dioxide, a cause of global warming. So said a major study commissioned by the Sutton Trust last year. One in five cars in urban areas during the morning rush hour is taking children to school - often just one. Streets are clogged, the fumes are choking, tempers rise, fists fly ... and that's just down our way.
"A huge amount of our journeys are under two miles, and there is a lot we can do in our own lives to walk and cycle more," said Mr Cameron, who has the luxury of living in the chi-chi Notting Hill area of London, with its excellent bus and Tube links and good schools on the doorstep. Those mild words were seized on as an attack on school-run mums in their Freelanders and Cherokees, but the Conservative leader is unlikely to say anything stronger. He turned down the greenest government-issue vehicle on offer because it wasn't big enough, and it now turns out that on those camera-friendly cycling trips to work he is followed by a car carrying his papers. And of course if you can afford a Chelsea Tractor as a second car, scattering pedestrians on the Fulham Palace Road like sheep in a field, then you are probably an affluent middle-class voter of the kind Mr Cameron's heart desires the most.
Paula is one of them. A company director, she does not want me to give her full name because "some people get over-excited" about her huge black secret service-style Chrysler which pumps out 318 grams of carbon dioxide for every kilometre she travels. That is almost twice the average emission for a car, 170g. Paula shrugged off the Chancellor's rise in tax on such vehicles as "puny", but she got really angry when what she thought was a parking ticket fluttering on the expansive windscreen turned out to be a clever fake from the Alliance Against Urban 4x4s, a campaign group that slaps them on offending vehicles. Bright yellow with a chequered border, it declared: "It ought to be a criminal offence to drive around town in a vehicle that does this much damage."
Paula works full time and she doesn't want to let her 12-year-old daughter walk to school, even through eerily quiet Surrey streets. "Not on her own, because I am petrified about what might happen to her. It's OK now, maybe, but what about in winter?" Milly Dowler was murdered after being snatched a short drive away. Paula's school run is much less than a mile, but, she says, "I can't walk there and back, I haven't got the time. I've got to be in work. So we go in the car. It's warm and safe."
Not necessarily. Air pollution can be worse inside the car than it is on the streets. Campaigners say 4x4s are 25 per cent more likely to be involved in accidents. And Steve Hounsham of Transport 2000 believes the threat of abduction is overplayed. "There has been stranger-danger hysteria," he says. "The chance of being abducted by a stranger while you are on your way home from school is minimal compared with the danger of being flattened by a car that is doing the school run." He believes there needs to be "a psychological softening-up of parents" to get more of us to accept the benefits of their children walking and cycling. "Everyone seems to agree on this," says Mr Hounsham, "but there is no great movement to find a solution."
Linda Howard rode the yellow bus as a child growing up in New York, and remembers 30 of them pulling up outside her school gates to be met by teachers with clipboards. But then more than half of American children take the bus, compared with 6 per cent here. Ms Howard is the managing director of First Group Student, which runs most of the yellow buses on British roads, and she agrees that most children prefer to be with their peers than their parents first thing in the morning. "Mum is always asking what they're up to or whether they've done their homework - you know, the sort of question that gets a shrug and a monosyllabic answer - but our research shows that 30 minutes on the bus to relax and chat to their friends makes them more settled when they get to school."
So what exactly is the difference between a yellow bus and a normal school bus then? One Surrey councillor laughed out loud when asked that question and said: "It's yellow. That's it!" Ms Howard disagrees, as you would expect. "There is a clear concept: it is about partnership between the schools, parents and the kids; the buses have a higher safety specification than usual; the drivers are trained to deal with children. A register is taken. There are seat belts. I could go on and on, but the point is, this is an environment made for the kids, it is the start of the school day. It's not just about transporting a load of widgets from one place to the next."
If they're so great, what's the delay? The Department for Transport says 90 more buses will roll out soon in Yorkshire, and £7.5m is being spent on advisers for schools who can help to organise such schemes. Three government departments would benefit from a national scheme but none is taking the lead. Neither Labour nor the Tories really wants to challenge school-run drivers. "There is a lot of pump-priming money going into feasibility studies and pilot schemes," says Ms Howard, "but we still don't know how a national network would be funded."
Prerna Abdaal waited eight months for a seat on her bus, which costs £48 return for a six-week period. It takes 15 minutes to travel narrow roads and mini-roundabouts to Fullbrook School, longer if the traffic is bad. "If she is late then it is their responsibility," says her mother. At first the children who had bonded together as regulars on the bus rejected Prerna as a newcomer. "They picked on her, and someone tried to trip her up on the steps of the bus. But the school had a word, and that has stopped." Jasmine does not drive, and her husband leaves for work early. "Without the bus there would be nobody to take my daughter to school."
Seven buses serve four schools in Runnymede, saving 280,000 rush-hour journeys this school year. The buses are sponsored by local businesses, including Proctor & Gamble. While they cost £230,000 to run, only £30,000 comes from sponsors. They were asked to pay more for extra buses, but declined.
A study on the Surrey scheme suggests that parents who were sharing cars have put their children on the bus. But the 22 per cent who were ferrying their sons and daughters to the school gates alone still do so. That is the real reason we do not see yellow buses across the nation. They're bright and good for photo calls, but even if councils provide them and businesses help to pay, parents still have to want to use them. And you know how it is: we're late, we're tired, it's raining ... we get in the car.
"I know this is a funny thing to say," says Paula the 4x4 driver, a former Blair supporter tempted by the touchy-feely New Tories, "but I feel at home in the car, and my daughter and I have a little chat and it's like we're at home right until the last minute. So what harm does it do, really? One car. The problems of the world are bigger than that, aren't they?"
A YEAR ON THE RUN
1 billion school-run car trips are made in Britain annually
500 million litres of fuel are consumed in private vehicles
2.1 million tons of CO 2 are emitted
570 million hours are spent doing the school run
WHAT THE BUS CAN DO
US-style yellow buses started serving the Magna Carta School in Surrey four years ago, one of the first schemes in the country
71 per cent of the 1,200 pupils live a kilometre or more from the school.
42 per cent of pupils used to travel to school by private car. Now it is 22 per cent.
120 pupils pay £1 a day each to ride in the seven yellow buses that serve the Runnymede area.
The percentage walking or cycling has risen from 42 to 48 since the scheme started.
This yellow bus scheme saved 186,000 school-run car journeys last year, easing congestion.