The towering wings of the yellow vultures have become a familiar sight for drivers on one of Scotland's busiest roads.Along a 32-mile stretch of the A77, scores of mounted cameras clock motorists' average speed.

Those who comply with strict limits are helping to make one of the country's most notorious roads safer, but those who refuse to slow down must face the consequences.

In nearly 10 years from January 1996 to December 2005, 30 people lost their lives in crashes on the A77. In just two years, since the system was introduced, that number has been halved.

Those behind the £1m cameras are confident this system is the best way to save lives - despite its unpopularity with some drivers.

Yet, as the controversy over the best approach to tackling speed on the roads continues, Swindon yesterday became the first town in the UK to do away with fixed-point speed cameras. Despite the town s plans to remove the devices, Scotland is unlikely to follow its lead.

According to Jim Dale, director of the Scottish Safety Camera Partnership, the body that decides where speed cameras should be sited through its eight local networks, the controversial technology is cutting speed - and saving lives - across the country.

In Scotland, there are currently 503 speed cameras in operation - four different types. These include fixed cameras, in their brightly coloured boxes; red light detection cameras, which only operate in Glasgow and Edinburgh; mobile units which clock drivers from vans and motorway bridges; and average speed cameras such as those on the A77, the first of their kind in Scotland.

According to Mr Dale, every single one of these cameras has played its part in this success. He said: "We wish Swindon good luck in their endeavours and will be keeping an eye on their fatality rates in the months to come, but I don't believe this is the approach we want to take.

"We've always taken a very consistent approach to speed cameras in Scotland. We only place them where there is a clear need - either because of the high number of accidents or an excessive number of motorists speeding.

"As far as the A77 average speed camera is concerned, it has been extremely successful. The trial of the camera finished in July and we are currently collating the results into a report.

"However, I am confident it will show excellent results. Very few motorists have been fined on this stretch of road, which means drivers are reducing their speed as they drive through it. This was previously an accident blackspot, so a reduction in speed can only be very good news."

Speeding on the A77 had been identified as a serious issue by road safety practitioners and was considered a significant factor in many of the serious crashes that had occurred on the road in recent years.

A local consultation exercise carried out in mid-2004 by the A77 Safety Group also revealed that speeding was one of the principal concerns raised by communities along the road. The Strathclyde Safety Camera Partnership was asked to join the A77 Safety Group in July, 2004, and it was hoped safety cameras would reduce the excessive speed of some motorists on the A77.

The system measures the time taken by individual vehicles to pass through sections of the route and takes a photograph of any that register a higher average speed than the limit allows.

The safety group analysed Scotland's first average speed camera system's "end-of-year-two accident and casualty numbers" within the 32-mile zone, which stretches from Bogend Toll, north of Ayr, to Ardwell Bay south of Girvan.

The report revealed the number of people being killed or seriously injured in accidents has been halved since the system was brought in, while all injury accidents have reduced by more than one-fifth. The effectiveness of the system will be fully assessed when three years "after" data is analysed in a report due later this year.

According to the data available to date, there have been nearly 24 million vehicle movements along the stretch in the two-year period, with just 320 people issued with notices of intended prosecution.

Mr Dale believes the success of the A77 camera system could lead to the technology being used elsewhere. "Obviously £1m is quite a restrictive cost, but there are currently a number of other, cheaper systems in development," he said. "We would look to use a similar system elsewhere, but only if there is a definite benefit."

It's not just on the A77 that the evidence appears to show speed cameras doing their job. "You only have to look at what's happened in our Northern Partnership area in the Highlands," explained Mr Dale. "In the three-and-a-half years before joining us, they had 37 fatal and serious road accidents at sites which required cameras. In the past three years, there's only been one fatal accident at the same sites.

"We consult with our partners, the police and local authorities, about every single camera that is sited, and then we monitor the effectiveness of the camera.

"If it is not doing its job, or is no longer needed, we take it away. Speed cameras are not a revenue-generating business. Last year, 86,000 paid fines, which equates to around £5.2m. However, that's £2m less than it costs the government to operate them.

"We should also remember that we estimate every road fatality costs £1.6m, while every serious accident costs £300,00, and that says nothing about the emotional cost to the families of those killed or injured." Mr Dale believes that Scots are getting the message when it comes to cutting speed.

He added: "As far as cameras are concerned, detection rates are down dramatically throughout the country. This means people are not being issued with fines because they are not speeding.

"For us, that's positive. We don't want to catch motorists out, we just want them to cut their speed." In 2000, the UK Government, with support from the then Scottish Executive, laid down tough new road safety targets.

They demanded a 40% reduction in those killed and seriously injured in accidents on our roads, with a 50% reduction in childrens' fatalities, by 2010.

Scotland has already met and exceeded these targets.

Conservative MSP Bill Aitken said Scotland's road safety chiefs had taken a more sensible view on the issue to some of those south of the border.

He said: "We all hate speed cameras, but I do think that in Scotland a more discriminatory approach is taken. The cameras installed here appear to be where necessary due to the number of accidents or excessive speeding.

"I n England, it appears to be more of a fundraising exercise in a number of places."

Isobel Brydie, of Scotland's Campaign Against Irresponsible Drivers, said the average speed system is a much more effective way of keeping the issue of speed to the fore of drivers' minds.

"People get to know where the fixed-point cameras are and simply slow down before they approach them," she said.

The average speed system is much more successful because it prevents people from speeding up before they get to the camera. Because they are placed along accident blackspots or dangerous roads, drivers are alerted to the fact they need to slow down."

Ultimately, the intended outcome of any road camera system is to save lives and reduce the number of accidents caused by speeding on Scotland's roads.

With a pilot system that has halved the number of deaths on one of the nation's most dangerous roads, the figures speak for themselves.

"So far, it seems like this is working here," said Ms Brydie. "If providing more average speed cameras can be justified to the public, I think they would be a welcome move towards saving lives."

It all began on a race track

Dutch company Gatsometer BV, founded by the 1950s rally driver Maurice Gatsonides, invented the first road-rule enforcement cameras. Gatsonides wished to better monitor his speed around the corners of a race track and came up with the device in order to improve his time around the circuit. The company also developed the first swimming timers.

The company developed the first radar for use with road traffic, and is the world's largest supplier of speed camera systems. Because of this, in some countries all makes of speed cameras are sometimes generically referred to as "Gatsos". They are also sometimes referred to as "photo radar", even though many of them do not use radar.

The first systems introduced in the late 1960s used film cameras to take their pictures. From the 1980s, mobile cameras were introduced. From the late 1990s, digital cameras began to be introduced. Digital cameras can be fitted with a modem or other electronic interface to transfer images to a central processing location automatically, so they have advantages over film cameras in speed of issuing fines, and operational monitoring. However, film-based systems still provide superior image quality in the variety of lighting conditions encountered on roads.