Last night at our children's school concert, a group of eight-year- olds took us back to wartime Britain as they played the part of schoolchild evacuees. No fruit or presents at Christmas, they explained, not even the chance to go home for the holidays. And they waved ration books at us to remind us how lucky we are today.
Amid news of the Government's failure to meet its climate change target, it struck me afresh that the parallel Tony Blair has been drawing between the Second World War and the war on terror would more appropriately have been drawn with the battle to halt global warming. Time will come when there is carbon rationing and it will be apparent, as it was to everyone during the Second World War, that it does matter that each citizen does his or her bit. Cutting carbon emissions isn't the only reason to ration our car use: research published this week reveals that congestion caused by the school run is responsible for nearly 7,000 deaths and injuries a year. Yes, driving your children to school increases the chances of someone being killed or injured.
If just one out of every 10 parents and carers who usually drive left their cars at home, 190 deaths and injuries could be prevented each year - that's one for every school day, says the insurance company MORE TH>N, which published the report.
The significant thing about this report is that it is saying congestion increases road danger. Road safety people used to say that congestion slows cars down and cuts accidents. Speed is definitely a factor in road crashes, but relying on something as random as congestion to reduce speed clearly isn't a strategy. There are other ways to cut speed, such as legal limits and traffic calming.
The findings of this study are supported by crash statistics in London since the congestion charge. The drop in deaths and injuries is significantly greater inside the zone than outside.
The irony is that parents think the roads are too dangerous to let their children walk. What we know now is that driving is adding to the danger.
The best way to protect children is to walk to school or, if the journey is too long, to walk for part of it. Walking with an adult is how primary school-aged children learn road safety. The highest number of deaths and injuries happen when children are 11 to 15 years old, because so many are travelling independently without the experience of coping with traffic as a pedestrian.
Walking reduces the number of cars on the road, which is healthier for all of us, and it gives a direct health boost to the child. It is no accident that obesity is on the rise at the same time that people are spending more time in the car.
So what to do with this information that driving our children to school is leading to deaths and injuries? Start a discussion about the merits of walking at the school gate and some mum will say: "But I have so much to do in the mornings that saving time by driving is the only way I can manage".
One can completely understand the sentiment and the sense of irritation at being put on the defensive: "Why should I have to feel guilty about this? It's tough enough juggling kids and a job as it is".
What we can do with this kind of data is let it inform the choices we make, rather than staying in the silo and doing what we have always done. Somehow we have to be able to say to ourselves: "I can justify driving my child to school, but I also know it would be healthier for us and the planet, and safer for everyone, if we walked. So I'll make a start by walking once a week (and even if it ends up being once a fortnight, that's better than nothing, and I won't beat myself up when I don't manage it)."
For parents who live too far away, parking 10 or 15 minutes away from the school and walking the last bit is also better than nothing, but obviously not an option for those who have to zoom off to work afterwards.
Standing back for a moment and consciously thinking through the issues helps us work out what is best for us as families, and us as part of society. And trying out new things can be liberating. As we used to get told, you won't know until you've tried. Sometimes walking is as quick as driving. There may be a great bus or train from the school to the office. You might lose weight. Your child might discover nature. If you walk, you will be fitter and more in touch with the community, and you will cut the risk of road danger and the pace of climate change.
Even with the knowledge that the school run is leading to more road crashes, and that cars are one of the main causes of climate change, our first impulse is to feel guilty and then try to forget all about it. Our second impulse needs to be to believe that every little bit helps, and if everyone uses their car a bit less, it will save lives and it will help the planet.
Rationing the school run does mean a sacrifice, but it offers an opportunity for change, and the chance to feel good inside and out.
Hester Brown is press and parliamentary officer for Living Streets, a charity that campaigns for better streets and public spaces