A new campaign to stop "man's best friend" from becoming a killer in your car is being launched by the Royal Society for the Prevention of Accidents.

Thousands of leaflets on carrying pets safely in vehicles have been produced by RoSPA.

The leaflet, funded by the Department for Transport, explains how unrestrained pets can be hurt or severely injure people in a car.

At 30mph, for example, a 50lb border collie would be thrown forward with a force equivalent to nine 12-stone men - enough to kill a driver or passenger.

RoSPA has taken advice from the PDSA - Britain's leading veterinary charity - which will help to distribute the information to pet owners and professionals. Road safety officers around the country will also have copies.

Unrestrained pets can distract drivers and cause accidents. After a crash they could escape from the car and be hit by passing vehicles or cause collisions

A frightened dog might attack a stranger going to assist an injured driver.

The leaflet gives information about safety harnesses, pet carriers, dog guards and travel cages or crates. It also gives other safety tips for pet owners, including dealing with emergencies.

Linda Morrison Allsopp, RoSPA Road Safety Project Manager, said: "People have been shocked by television advertisements showing a teenager not wearing a seatbelt in a rear seat being flung forward and killing the driver. But they don't seem to realise that the consequences can be just as horrific if a dog is unrestrained in a car. In a crash a pet can be like a canine cannonball.

"It is important that a pet is safely restrained to ensure its safety, the safety of the people in the car and other road users."

The leaflets are available from RoSPA, and can be found on the Society's website www.rospa.com