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No liability is accepted for errors or inaccuracies in any of information contained on this website. 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.

 8th April 2014

High Friction (Anti-skid) Surfacing & Coloured Cycle Lanes

High Friction (HFS) or Anti-skid Surfacing is a proven road surface treatment that increases skid resistance and reduces braking distance, thereby reducing the potential for accidents. It has a long history of proven use having first been used in the UK in the late 60’s. HFS incorporates a 1mm to 3mm 70+ PSV Calcined Bauxite aggregate. Calcined bauxite is an extremely durable & hard aggregate. It retains the sharp edges produced at the time of crushing for the life of the treatment. This greatly enhances the skid resistant properties of these surfaces over the use of natural aggregates. Calcined Bauxite has a long proven track record of performance. The Calcined Bauxite is available in a buff or grey colour. In Ireland, the preference has been for the buff colour whereas in the UK both buff and grey are widely used.

 There are two main system types of HFS.

  1.  Cold Lay normally using an Epoxy Resin Binder or occasionally a Polyurethane Binder
  2. Hot Lay using a Thermoplastic Resin

 The cold lay system involves the application of the liquid binder onto the road surface, normally hand applied by squeegee. This is followed by the application of an excess of Calcined Bauxite aggregate over the binder. After the binder has set, which can take between two and six hours depending on temperature, the excess aggregate is removed by vacuum sweeper or other means.

 The hot applied system comprises a thermoplastic rosin ester binder incorporating a 1-3mm Calcined Bauxite aggregate, buff or grey. The material is generally pre blended in meltable bags. It is melted and mixed in a suitable boiler fitted with thermostatic controls & a horizontally mounted agitator. The product is normally hand applied to the road surface using a screed box with a suitably designed trailing edge to give a nominal applied finish of 5 mm by combing transversely across the road surface. The material sets in less than half an hour, after which it can be subjected to traffic.

HD36 provides guidelines for where HFS should be used, dependant on road type, traffic volumes and application (e.g. major junction approach). The minimum applied length for HFS is generally 50m. However this can be increased to up to 100m depending on the local criteria, design speed, application type, sightlines etc.

The specification for HFS is contained in Clause 924 of the Specification for Roadworks. In the Republic of Ireland, NRA Clause 924 stipulates that the HFS can only be an epoxy or other approved resin compound and that the aggregate shall only be calcined bauxite. The Irish specification therefore precludes the use of the hot lay system on national roads and motorways. The UK specification utilises a performance criteria under BBA HAPAS. Under the UK specification, both cold lay and hot lay systems can meet Clause 924 requirements for Type 1 traffic levels. A very important point in relation to BBA HAPAS is that both product and installer must be BBA approved for the system to comply.

In practice, notwithstanding NRA Clause 924, hot lay systems have been used on some major roads in Ireland. Hot lay systems can be laid year round, subject to a dry frost free surface. Cold lay systems can typically only be laid between April and October because of the more onerous weather constraints.

Where coloured cycle is required, it is generally red in colour. Other applications for red surfacing include advance stop junctions, traffic calming, bus lane demarcation etc. The application systems are similar to HFS except for the aggregate type. Generally the aggregate used is natural red granite with a typical PSV in the high 50’s. Where a Red High Friction Surfacing is required, there are two options.

(a)    Use a cold lay system and pigment the bauxite

(b)   Use a hot lay system with red pigment.

Option (a) is substantially the more expensive option as it involves specialist pigmentation of the aggregate. Option (b) is relatively straightforward as it merely requires the addition of a red pigment to the thermoplastic HFS during heating and mixing in the boiler.