IT is analyst Kevin Bolan's job to identify the roads most in need of speed cameras.

Using a computer system linked to police headquarters in Devizes, he can probe the safety record of any road in the county.

Coloured stars on a map mark areas of tragedy and misery, where people have died or been seriously injured in road crashes.

Mr Bolan said: "There were seven murders in Wiltshire last year compared to 43 road deaths.

"It doesn't matter to families how people die, they have lost loved ones."

Despite receiving almost daily pleas for speed cameras from worried communities, unit officers have to work on hard facts, not emotion. The first move is a printout of crash circumstances which will point to whether speed was a factor before a stretch of road is picked for monitoring.

Guidelines state there have to be eight injury crashes, four of them causing serious injuries or death, per kilometre of road within a three-year period to qualify for a fixed speed camera. For a mobile speed unit, four injury accidents must have occurred, with at least two involving serious injury or death.

When speed checks are carried out, more than 20 per cent of drivers need to be speeding before analysts look at what is known as the 85th percentile if 85 per cent of all vehicles are speeding at 10 per cent plus two over the set speed limit further action can be taken.