RSTA chief: Plan ahead to prevent cracks on smart motorways

09/07/2019
Dominic Browne

A senior figure in the sector has called for more proactive asphalt protection planning in utilities works and smart motorway upgrades - warning that a lack of early investment could see cracks appear in motorways.

Speaking at the annual Institute of Highway Engineers conference, Mike Harper, chief executive of the Road Surface Treatments Association (RSTA), highlighted that on the first smart motorway project on the M42 - opened in 2006 - large cracks opened up in the carriageway some 20mm wide.

As smart motorways upgrade the hard shoulder and turn it into a running lane 'it has the effect of moving the other three lanes across slightly' he said - so joints that were under the white lines move into the running lanes and suffer more stress.

Road resurfacing wasn't planned for the original M42 scheme when it was delivered, and as a result the joints in the newly formed running lanes opened up very quickly.

'We ended up with a joint that was 20mm wide, you could stick your fingers in it, and with chip loss on the surface,' Mr Harper said, adding that the then Highways Agency decided to treat the joints across 18km of road along a 'prepared 150-200mm wide area in situ'.

The treatment was still effective years later in keeping the joints sealed and protecting the asphalt, however he warned the sector could face similar problems once again as money becomes tight.

Speaking to Highways he said: 'When there was a lot of money for smart motorways, the plan was to plane off and do new surface courses and so put the seams back on the new locations of the white lines.

‘Now they are now going back to utilising existing road surfaces rather than routinely planing everything off. So we are going back to that scenario where we will need to protect those seams.

'There is a section where I live in Cheshire where a team had taken off some of the temporary lining with a hydro blaster and they had taken the matrix of the asphalt out straight away on a brand new surface.

'There is a seam that is already open and this motorway had literally been open for two days. It is a real risk. It is so low cost at that point to protect that seam. What I would like to see is more proactive use of crack and joint repair materials over seams - not just for motorways but for reinstatements in the utilities sector.

'Water blasting can take some of the bitumen away. It can be very useful for tackling "fatty" services. but on white lines it can take some of the bitumen away. We know that is going to happen. It should be part of the programme that when we move those joints then we should protect them rather than leave them to fail, otherwise we are wasting our money as taxpayers.'

Highways England has carried out a competition leading to road trials of new solutions to remove white lines that cause less damage to the road surface.

A Highways England spokesperson said: 'Smart motorways are good for drivers; they add extra lanes giving extra space in a cost effective way and means that technology can be used to make journeys safer and more reliable. Highways England plans to continue their development into future years.

'Highways England is proud to operate and maintain some of the safest roads in the world, and strive to design road surfaces with a good lifespan, providing overall good value for money and environmentally sympathetic characteristics. Our specifications provide details of best practise and clear instruction for the position and construction of joints to avoid premature distress and ensuing rectification of joints.'

The current version of Clause 903, Specification for Highways Works Volume 1 states that where an existing road pavement is resurfaced, joints in the surface course should coincide with either the lane edge, the lane marking, or the middle of a traffic lane, whichever is appropriate. Joints must not coincide with the wheel path.

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