AVERAGE speed cameras are set to go live on one of Scotland's busiest motorways from Monday as part of a £500 million overhaul which aims to cut congestion and shave 18 minutes off the journey time between Glasgow and Edinburgh.

The cameras will go live on the northbound and southbound carriages of the M74 between Junction 6 Hamilton and Junction 3A Daldowie from July 20. They will remain in place until 2017 to allow for the construction of a new lane and hard shoulder along this stretch of the motorway.

As a result, motorists will be left with three narrow lanes.

Transport Scotland said the safety cameras will encourage a "safe and steady" traffic flow.

Average speed cameras were first used in Scotland during road works on the M74 in 2006, but were used more recently during upgrades to the M80 and were rolled out on the A9 last year to cut speeding.

The cameras will also be rolled out on various stretches of the M73, M8 and A8 in the months ahead.

It comes as work on the M8 M73 M74 Motorway Improvements Project is ramped up.

The £500m scheme, scheduled for completion in Spring 2017, will see a new section of M8 built between Baillieston and Newhouse, as well as delivering significant improvements to the Raith Interchange in Lanarkshire, Shawhead Junction, and widening key sections to the M8, M73 and M74.

The motorways carry some 100,000 vehicles per day and the project is designed to improve traffic flow across the Central Belt by cutting congestion and reducing the journey time between Scotland's two biggest cities from around 40 to just over 20 minutes.

Chief Inspector Fraser Candlish of Police Scotland, said: “The reduced speed limit is necessary to ensure that drivers are able to cope safely with the inevitable effects of the road works such as narrowed lanes, changing lanes, contra-flow and construction traffic. Highly visible average speed cameras are an effective way of encouraging motorists to respect the reduced speed limit.”

Graeme Reid, Project Sponsor for Transport Scotland, said: “We know from our experience of major road infrastructure projects that safety cameras are a tried and tested approach that improves safety for both road users and the adjacent construction workforce during what will be an extremely busy period in terms of construction.

“Not only do the cameras create a safer environment for all concerned, they can also help improve the flow of traffic through the works. With more than 100,000 vehicles using these key routes each day, we are acutely aware of the challenges involved in keeping the traffic moving whilst delivering a project of this scale and complexity. However we will continue to work closely with Scottish Roads Partnership to ensure disruption is kept to a minimum.

“Once complete, congestion across the central Scotland motorway network will be significantly reduced, with travel time reliability between the main route of Glasgow and Edinburgh improved.”

The contract to deliver the improvements has been awarded to the Scottish Roads Partnership, a consortium of Ferrovial Agroman and Belfast-based Lagan Construction Group.

Ferrovial Agroman, headquartered in Dublin, is also in charge of the design and construction of the new T2A terminal at Heathrow Airport, while its BFK consortium is involved in three Crossrail projects in London.

SRP spokesman, Mark Miller, said: “Given the close proximity to the live road and the space constraints across the site, we believe that it is necessary to install safety cameras and reduce speed limits to ensure the safety of road users and that of our workforce. We would like to take this opportunity to thank road users for their patience while we deliver these significant improvements works.”