Lisa Salmon looks at the weird, wonderful and sometimes weary world of family life.

Having your child mown down by a vehicle and killed or seriously injured is any parent's worst nightmare.

For the parents of 2,540 UK children last year, that nightmare was a devastating reality.

In 2009 alone, 70 children were killed by a vehicle while walking or cycling and 2,470 were left with serious injuries, including paralysis, brain damage or limb loss, according to road safety charity, Brake.

In addition, another 11,179 children were left with cuts, bruises and mental trauma from being hit by a vehicle while walking or cycling, often on their way to or from school.

That's 13,719 children killed or injured in just one year.

Many of them were hurt by speeding drivers, and that's why the theme for this year's Road Safety Week (November 22-28) is Kids Say Slow Down.

Ellen Booth, campaigns manager for Brake, the road safety charity that runs the week, says the charity believes that 20mph should be the default speed limit for towns and villages, especially around homes, schools, shops and community facilities where there are likely to be pedestrians and cyclists.

She says: "The reason 20mph is so important is not that you'll hit a child with less speed, it's that at 20mph you stand a significant chance of stopping before you hit the child."

"There's no speed that's safe to hit a child, but you want to be driving at a speed where you have the opportunity not to hit them."

At 20mph, drivers have a good chance of stopping in time if a child runs out three car lengths in front of them.

At 30mph, it takes about six car lengths to stop.

"Any faster than 20mph, and you would hit that child and have a significant chance of killing or maiming them," warns Booth.

"The theme Kids Say Slow Down emphasises that it's children speaking out this year to tell drivers that they want them to slow down."

Schools around the country are using Road Safety Week to campaign for either a 20mph limit outside their school, speed cameras or traffic calming measures.

"All the schools involved have either had a child run over and killed, or are worried that it might happen because of the dangerous road outside their school," says Booth.

"It's very much about local communities speaking out."

There are already 20mph speed limits in various areas around the country - York, for example, is currently implementing some trial signed only 20mph speed limits in various locations across the city.

And a recent study of the 399 20mph zones in London showed that the zones are very effective at reducing casualties on the roads where they are placed - and also on surrounding roads.

The study found that introducing the zones resulted in a 41.9% reduction in all road casualties, and a 50.2% decrease in the numbers of children aged under-15 killed or seriously injured.

Casualties in areas adjacent to 20mph zones also fell slightly, by around 8%.

"They're proven to make a huge difference to the safety of pedestrians, cyclists and child casualties," says Booth.

She acknowledges that reducing speed limits is a controversial step, but stresses: "I think the vast majority of people understand that driving faster is more dangerous, and that if they do hit someone, they're more likely to die."

"But still a lot of people drive fast, even though they know there are consequences - they understand the message, but they're not committing to it and changing their behaviour."

She stresses that many of the drivers Brake is trying to educate during Road Safety Week are parents themselves, adding: "They'd be absolutely horrified if their child was knocked over - especially if the driver was speeding.

"But they might find themselves speeding from time to time in other people's neighbourhoods."

"This is about getting drivers to assess how they're driving themselves."

Another major part of the campaign is getting the Government to listen, she says, pointing out that last year the Government did approve speed cameras for 20mph zones.

Before that, the only way of enforcing the zones was by using traffic calming measures such as road humps.

She adds: "It's hard to get any kind of substantial change through Government - everything takes a long time, but it's a case of continuing to press and show that the public really want this."

Ask the expert Q: "If we only have one child is he likely to be lonely, or could he benefit from having our sole attention and not fighting with siblings?"

A: Dieter Wolke, a professor of Developmental Psychology and Individual Differences at the University of Warwick, says: "Like most things in life, there's no clear-cut benefit or disadvantage from having or not having siblings."

"Siblings can be supportive to each other and while they sometimes have less contact in early adulthood, they often become closer again in later adulthood, when they have children themselves, their parents are old or have died."

"Thus they can be a resource and help you through difficult periods in your life. On the other hand, on average, children experience more physical violence from siblings than from anyone else during their life. A recent study by the University of Essex and Warwick found that 54% of siblings are involved in weekly bullying - from being hit to called nasty names."

"Being bullied at home doubles the chance to also be a victim at school, and makes you less happy."

"But it really depends on the constellation of siblings and their spacing (how far apart they are in age). An older sister is usually a good thing, most likely to be caring to younger siblings. In contrast, brothers closely born apart have the most conflicts and fights."

"Thus, the relationships at home are a training ground for how a child deals with peers. Parents need to be fair, firm, consistent and loving arbitrators to help their children along."

"Single children get more attention from their parents, but the parents often spend more time to find playmates and holiday companions for their child."

"However, attention and high expectations can be burdensome as they grow older."

"On balance, what matters is the temperament of their child/children and how the parents deal with their single child or several children."