Parents are being urged to put their children into rear-facing safety seats until they are three or four years old.

According to Volvo's investigations, a forward facing child seat provides around 80% better protection than if no child restraints are used, whereas a child in a rear-facing seat is approximately 90% less likely to be seriously injured in an accident.

The Swedish car maker has stressed that children and babies are not small versions of adults - and they need special restraints designed for their developing anatomies.

Relative to the body, the head of a newborn baby makes up half the total body weight, whereas an adult's head weighs only about six per cent of the total.

This oversized head - in combination with developing neck vertebrae, muscles and ligaments - is a child's weak point and is prone to injury in crashes.

When travelling in a rear-facing seat, the crash forces are spread over the back and head, which reduces the load on the neck and greatly decreases the chance of severe neck and spinal injury.

Another vulnerable area is the pelvis, which is underdeveloped and cannot hold the safety belt in position as easily as an adult's hip area, so child booster seats greatly improve the correct belt geometry.

The positioning of the safety belt is important so that the occupant is restrained over the body's stronger areas like the upper torso and pelvis - protecting the weaker parts of the body such as the abdomen.

The lap belt should be placed tightly across the pelvis, as low as possible towards the thighs and not over the soft tissue of the abdomen. The torso belt should run across the chest and also be pulled tight.

It does not matter if the belt touches the neck. Never place the torso belt under the arm or behind the back.

A booster seat gives a child an increased height and directs the safety belt over the stronger parts of the body during a crash.

Volvo has produced a definitive a free downloadable guide to in-car safety, especially for children and pregnant women, which includes short video guides and practical tips for parents and parents-to-be. It is available at www.volvocars.co.uk/childsafety.

A booklet of the Children In Cars guide 1 can also be requested by calling the Volvo Information Centre on 0800 400430.