New and old riders are being targeted

It comes in response to a sharp rise in the number of riders badly injured in crashes in the last two years.

Posters will be displayed on the back of buses in the Avon, Somerset and Gloucestershire police force areas.

A total of 633 motorcyclists were injured in road accidents in these areas in 2003, with 20 deaths and 239 people seriously injured.

Injuries to riders have increased with the rise in motorcycles being used for commuting and leisure.

Many of the born-again bikers have not ridden for a while and tend to forget that bikes are more powerful these days Dave Gollicker, Safety Camera Partnership

Road safety experts say many of the accidents are caused by loss of control or dangerous overtaking.

Riders using excessive or inappropriate speed for the road conditions is also a major factor.

Dave Gollicker, of the Safety Camera Partnership, which is behind the campaign, said: "Motorcycling is very safe and enjoyable, provided riders are sensible and adjust their speed to the road conditions.

"If they don't, they run the risk of killing themselves or someone else."

Riders who have rediscovered motorcycling after a break of several years are also being targeted in the campaign.

"Many of the born-again bikers have not ridden for a while and tend to forget that bikes are more powerful these days and that road conditions have changed with an increase in the volume of traffic," said Mr Gollicker.

"They need to familiarise themselves with their machine and get used to the braking, acceleration and general handling."