M3 smart motorway technology goes live | Smart Highways Magazine: Industry News

M3 smart motorway technology goes live

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The technology element to the £174m M3 smart motorway project between junctions 2 to 4a has gone live and a 70mph speed limit established across to the entire road.

The upgrade converted the hard shoulder of a 13.4 mile section of the M3 between Farnborough and the M25 to an extra traffic lane, with construction being completed last month.

However Highways England said that due to an expanded remit for the scheme there had been a delay in implementing the smart element, which includes technology in overhead gantries to detect incidents, actively manage traffic and inform drivers about conditions ahead.

A 50mph speed limit was in place while Highways England carried out testing.

The smart technology has now been launched and will start ‘setting the speed limit to match conditions and helping spot any queuing traffic, incidents or broken down vehicles’, Highways England said.

A spokesman told Smart Highways that the extra work added to the M3 scheme included 13.4 miles of four lane resurfacing on each carriageway and demolishing and rebuilding the Woodlands Bridge at Windlesham.

Transport minister, John Hayes, recently told Parliament that work ‘on the further M3 smart motorway scheme between Junctions 9-14 is expected to start in 2019/20 and complete by 2021/22’.

A Stress Absorbing Membrane Interlayer was used on the running lanes for the M3 smart motorway project in Surrey.

Consultant Aecom specified asphalt reinforcement in the pavement design. Tarmac, subcontractor Foster Contracting and Tensar International proposed Tensar’s Stress Absorbing Membrane Interlayer (SAMI) Glasstex solution and supported the required departure from the standard process.

‘The SAMI adds tensile stiffness, increasing pavement strength at low strain and mitigating reflective cracking from both traffic-induced stress and from defects in the underlying pavement structure. It also acts as a moisture barrier,’ Tensar highways manager Craig Andrews said.

A total of 300,000m2 of Tensar’s Glasstex P100 composite was laid. This composite of glass yarn grid and paving fabric formed an interlayer between the fractured substrate and the asphalt overlay.

‘The Glasstex adheres to the underlying pavement structure using a straight run bitumen (160/220 pen) bond coat, with a calibrated spray rate of 1.1kg/m2, to activate both stress relief and interlayer barrier functions [as given by BS EN 15381: 2008], with reinforcement provided by the grid,’ Mr Andrews said.

Using the composite means the reconstruction depth is far shallower saving time and money. On the M3 it is just 120mm to 150mm, rather than a minimum 360mm with a standard approach.

 
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