Accreditation of proprietary products through the Highway Authorities Product Approval Scheme (HAPAS) has gained substantial momentum since its inception in 1995.
Approval procedures are now in place for seven out of eight product groups covered so far and more are likely to be embraced by the scheme as demand for technical approval widens.
HAPAS was established by the British Board of Agrement (BBA), the Highways Agency and the CSS - formerly the County Surveyors Society - to provide an independent product accreditation system applicable to the whole of the UK's road network.
The HA is responsible for running Britain's motorways and all-purpose trunk roads but, being gradually reduced in terms of size and budget,was looking to relieve pressure on its own approval system, according to the head of the BBA's materials and building physics division Steve Kelly.
'The HA is distancing itself from product approval and is very keen to encourage suppliers to sign up to the HAPAS scheme,' he says.
'This is becoming more relevant with detrunking and further privatisation of road management on the horizon.'
Both the CSS and the HA recognised that a new approval scheme was also needed to promote the use of proprietary products. These were becoming more prevalent at the time, driven by the replacement of recipe-based specifications with performance specifications.
A further requirement was maintained assurance of end performance, Kelly says.
'One of the main beneficial features of HAPAS is its regime of twice yearly rechecking and auditing of quality control measures to provide assurance that approved product manufacturing processes are being maintained. This is something the HA was not able to do.'
In 1995 the BBA's Highways Technical Advisory Committee (HiTAC) established specialist groups to produce guidelines for testing and approval of high friction surfacing (known as SG1), overband sealing and crack repair (SG2), thin surfacing (SG3), modified binders (SG4) and cementitious repair systems (SG5).
Product categories have since been added for parapet anchorages (SG6), bridge deck waterproofing (SG7) and Permanent Coldlay Surfacing Materials (PCSMs). A specialist group, SG9, has developed a method and ageing criteria for testing colour retention of pigmented surfacings.
Specialists invited to attend each group vary depending on the product, says Kelly. But, generally, each specialist group contains representatives of relevant trade associations, the CSS, BBA, Transport Research Laboratory and the Highways Agency on behalf of the Scottish Office, Welsh Office and the Department of Environment in Northern Ireland.
Guidelines produced by the specialist groups and approved by HiTAC are published in working draft form and applications can then be invited for HAPAS approval. Materials and product testing is carried out by one of several testing houses recognised by the BBA and accredited by the United Kingdom Accreditation Service (UKAS). The first round of product approvals in each category is then used to gauge the effectiveness of the guidelines and revisions are made if necessary.
HiTAC approval of the colour retention test produced by SG9 has allowed the BBA to create a ninth product category for resin bonded coloured surfacing, says Kelly. This was previously left out of the high friction surfacing work due to lack of a reliable test system for colour retention of pigmented materials.
'We are currently inviting members for SG10 to develop guidelines for approval of resin bonded coloured surfacings,' he says. 'SG1 will be reconvened this year to revise the high friction surfacing guidelines to include coloured materials and negative surface texture.'
Demand for HAPAS accreditation has varied across the product groups, says Kelly. For instance, uptake of the scheme has been slow for cementitious repair systems and modified binders. The HA, which is keen to get more suppliers to come forward, will be insisting that all products in these categories must be HAPAS accredited for use on its network from January and March 2001 respectively.
Approval of other products through the scheme will become mandatory for HA roads as and when a buying choice of three or more is available and the CSS is strongly recommending that its members do the same for non-trunk roads, says Kelly.
'Market conditions are having a strong influence on demand for HAPAS accreditation while it is still optional,' he says. 'The best case in point is proprietary thin surfacings, which have taken over from hot rolled asphalt as the preferred asphaltic material for resurfacing worn out carriageways.'
Thin surfacings, which are laid to nominal thicknesses of 40mm or less and based generally on stone mastic technology, produce a negative and noise reducing surface texture. Their use has risen dramatically since publication of the 1998 New deal for trunk roads White Paper, which set out the HA's policy of specifying low noise road surfaces when possible.
They have gained further popularity because negative texture reduces spray and the materials' premixed nature reduces plant and laying time by precluding the need to roll chippings into the surfacing.
'Demand for HAPAS approval of thin surfacings took us by surprise,' says Kelly. 'We started approval procedures in April 1999 and we now have more than 20 applications and the number is going up all the time.'