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Grey HFS at Dangerous Bend
Stage 1 – Assessment of applicant’s data
product approval system in UK or Ireland for the use of HPSVA in situations where HFS would normally be required.
consequential loss of life. The author believes than many high risk locations where HPSVA has been installed will subsequently be overlaid with HFS to prevent & reduce further accidents.
Stage 2 – Assessment of factory production control
FEATURE High Friction Surfacing
Stage 3 – Laboratory testing (and optional tests)
Stage 4 – System installation trial Stage 5 – System performance trial
It has become industry practice in many areas to use HPSVA at locations where HFS would have been previously applied. The principal reasons are the perceived cost saving and the mistaken belief the high PSV equates to long term skid resistance. There is no accreditation system for HPSVA installed in lieu of HFS. Notwithstanding this roads authorities, PPP/DBFO companies, motorway maintenance companies & local authorities are sanctioning the use of HPSVA at high skidding risk locations. Surely there needs to be a similar accreditation system for HPSVA as there is for HFS? A particular aggregate & binder HPSVA should have to undergo a rigorous performance evaluation before it can be approved for use at high skidding risk locations.
Roads authorities have an obligation to take such steps that are reasonably required to ensure the safety of the network. Will the current practice mean that roads authorities, PPP/DBFO contractors, designers, road safety auditors & local authorities become embroiled in litigation because of a short term decision to replace HFS with HPSVA at high risk locations?
(if applicable)
Stage 6 – Certification
Discussion
The criteria for laboratory performance testing include wear, scuffing & tensile adhesion. A two year system performance trial must be undertaken on site.
At the end of the two years, the system must meet minimum criteria including Skid Resistance Value (SRV), texture depth, tensile adhesion, erosion index & visual assessment. In Ireland, Transport Infrastructure Ireland (TII) introduced a new HFS specification in 2015. This includes a thorough approval procedure for HFS. TII publication DN-PAV-03075 sets out requirements for the approval of specific products such as HFS, which are not covered by a harmonised technical specification. A proposed Contractor system has its performance evidenced by a prTAIT (provisional Type Approval Installation Trial). The prTAIT consists of a defined section where HFS has been installed using Factory Production Control (FPC) and which has been subjected to in-service performance annually over a five year period. Testing following installation and one year later include SRV, texture depth, Pull Off Test, Shear Strength Test & visual assessment. After this period, detailed information is recorded to clearly identify the product, its performance and the intended uses.
What follow up SCRIM testing has been carried out on previously laid HPSVA sites?
Disclaimer: No liability is accepted for errors or inaccuracies in any of information contained in this article. All views or opinions expressed are personal to the author who does not purport to speak for, or represent, any professional body or organisation. Reliance should not be placed on any material contained in this webpage without first seeking and obtaining further professional advice.
John Cagney is an experienced Chartered Civil Engineer with expertise in High Friction & Coloured Surfacing, Surface Treatments, Bituminous Surfacing & Road Materials.
Council Journal 45
Unlike HFS, there is currently no
As stated previously there can be major performance differences for surface courses with aggregates of similar PSV but from different sources. High PSV asphalt is not a like for like replacement for HFS and does not provide a guarantee of skid resistance over the service life. Whereas it may be appropriate for some lower risk locations, it is neither a better whole life cost option or an equivalent to HFS at high risk locations. It is the author’s belief that the current widespread practice will result in numerous preventable skidding related accidents and