Sussex Police today dismissed claims they are "persecuting" motorists by using the force's helicopter to spy on speedsters.

As first reported by the Argus last month, police have equipped their £3 million helicopter with time-distance monitors that can trap speeding motorists.

One national newspaper this week accused the force of "persecuting and bringing more misery to beleaguered drivers".

But a force spokesman said today: "They should speak to families of those killed on our roads and they will know what real misery is."

Superintendent Jim Hammond, head of the force's traffic department, said: "Three motorcyclists died in Sussex last weekend alone.

"Besides the grief caused to the victims' families, there is a huge financial cost - £1 million for each fatal accident."

The helicopter crew is checking on motorists during speed crackdowns and occasionally during its return journeys after attending incidents.

But the force stresses that the helicopter crew is not assigned to carry out checks full time.

The force, East and West Sussex County Councils and the Highways Agency have painted 150 sets of spots, each the size of large saucepan lids, on main roads where speeding is a problem.

Each set is half a mile apart and patrol-car and helicopter crews use the markings to calculate motorists' speed.

They switch on the PolicePilot when the suspect vehicle crosses the first set of dots and switch it off when it passes the second.

The high-tech equipment then calculates the vehicle's speed.

A video camera films the offence as additional evidence.

Helicopter crews then contact ground-based colleagues who will stop and book the offending motorists.

PC Bernie Belford, the traffic officer who first came up with the idea of marking the roads, said: "The system is another weapon in our armoury to get motorists to drive more safely.

"Motorists won't know whether they are being watched so, hopefully, this will act as a deterrent.

"If it slows just one speedster down and perhaps saves just one life, then it will have all been worthwhile."

The A24, with its long stretches of straight road, has become a favourite route for many speeding motorcyclists. It is even listed as a "good ride" on an internet website.

More speed dots have been painted on the A24 in the past month than any other road in the county.

It has been marked every half a mile from Broadbridge Heath junction to the Southwater bypass and from Bush Barn crossroads to Findon.

PC Belford said: "One motorcyclist on the A24 was clocked doing 147mph.

"We have found that born-again motorcyclists, usually middle-aged men, are the ones most likely to speed.

"I want to stress that we are not out to persecute motorists. We want people to enjoy travelling on Sussex roads - but safely."

More than 1,000 people suffered serious injuries and 93 people were killed on Sussex roads last year. Excessive speed was a factor in one third of them.