The History of High Friction Surfacing

The development of modern high-friction surfacing in the UK stretches back more than six decades. One of the earliest significant UK road trials demonstrating the performance of HFS took place in 1959, as highway engineers looked for ways of improving skid resistance at locations where conventional road surfaces could not provide sufficient grip.

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As traffic volumes and vehicle speeds increased, high-friction materials became increasingly important around junctions, crossings, bends and other locations subjected to severe braking and turning forces.

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Over time, two principal approaches emerged: hot-applied thermoplastic HFS and cold-applied thermosetting resin HFS. The cold-applied category itself developed through several generations of resin chemistry, including epoxy, polyurethane/polyurea, MMA and polyurethane-modified MMA systems.

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This evolution has progressively moved the industry towards systems capable of combining exceptional skid resistance with improved adhesion, durability, application control and reduced disruption during installation.

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Hot-Applied High Friction Surfacing

Hot-applied systems represented an important stage in the development of HFS and continue to be used today.

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In a traditional hot-applied system, aggregate and thermoplastic resin are combined and heated to a high temperature before being screeded onto the road surface. By contrast, cold-applied HFS uses a liquid reactive resin binder applied directly to the substrate, with the high-friction aggregate subsequently broadcast onto the resin.

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Hot-applied technology can provide rapid installation, but the process inherently requires considerable heating of the material and specialist hot-application equipment.

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Cold-applied reactive systems avoid the need to heat the binder to thermoplastic application temperatures and have consequently become an important alternative, particularly for demanding high-friction applications.

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Epoxy High Friction Surfacing

Cold-applied epoxy resin systems represented a major development in HFS technology.

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Epoxies can provide strong adhesion, hardness and good durability and established themselves as an important binder technology for high-performance anti-skid surfaces.

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However, conventional epoxy chemistry has limitations. Cure can be comparatively slow, particularly as temperatures fall, while some formulations can be relatively rigid and sensitive to application and substrate conditions.

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Historic UK highways guidance recognised that polyurethane resins could provide greater flexibility and adhesion than epoxy resins and did not age-harden to the same extent, illustrating the progression towards alternative cold-applied technologies.

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MMA High Friction Surfacing

Methyl Methacrylate (MMA) technology provided another route to rapid-curing cold-applied HFS.

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Its principal advantage is speed. MMA systems can react very quickly, making them attractive where road closures and traffic-management periods need to be minimised.

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However, MMA chemistry also introduces practical considerations. The characteristic strong odour associated with methyl methacrylate can make installation more difficult in built-up or sensitive locations, and peroxide initiators used with some systems require careful handling and storage in accordance with their specific safety classifications.

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The extremely rapid reaction can also mean relatively short working times, making installation control particularly important.

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Polyurethane – A New Generation of Cold-Applied HFS

Polyurethane technology provides a different balance of properties and has become an established binder chemistry within high-friction surfacing. The RSTA/ADEPT HFS Code of Practice specifically recognises cold-applied polyurethane/polyurea alongside epoxy, MMA, polyurethane-modified MMA and hot-applied thermoplastic technologies.

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For road surfacing, the combination of adhesion, toughness and flexibility offered by polyurethane is particularly valuable. A road surface is not completely static: it experiences vibration, thermal movement, traffic loading and substantial localised stresses as vehicles brake, accelerate and turn.

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A high-friction binder therefore needs to do considerably more than simply stick aggregate to the road.

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StarPolymers HFS

StarPolymers HFS is a high-performance, cold-applied, three-component polyurethane High Friction Surfacing system developed for demanding highway applications.

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Rather than relying upon heat to soften and apply a thermoplastic binder, StarPolymers HFS uses controlled reactive polyurethane chemistry. Once its components are correctly mixed, the liquid resin is applied directly to the prepared road surface before the specified high-friction aggregate is broadcast onto the uncured binder.

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The result is a strongly bonded, highly textured surface designed to provide exceptional tyre grip in areas where braking and turning forces place particularly severe demands upon the road.

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Why Cold-Applied Polyurethane?

The choice of a cold-applied polyurethane binder provides several important practical and performance advantages.

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Because the material cures through a chemical reaction rather than having to be heated and subsequently cooled like a thermoplastic system, there is no requirement to heat the HFS binder to the high temperatures associated with hot-applied surfacing.

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This has several potential benefits:

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• No hot-melt boiler required for the resin binder

• Substantially less process heating at the point of application

• Reduced risk of heat damage to the underlying road surface

• Excellent adhesion to correctly prepared substrates

• Good flexibility and toughness

• Resistance to the severe braking and turning forces encountered at HFS locations

• Controlled cold application

• No MMA-type monomer odour

• No MMA peroxide catalyst system

• Suitable for demanding high-friction applications

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The environmental advantage can also be significant. Hot-applied technology requires energy to heat the material to application temperature, whereas a cold-applied reactive polyurethane system eliminates this particular installation-stage heating requirement.

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Three-Component Technology

StarPolymers HFS uses a three-component system to provide controlled, repeatable mixing and application.

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The components are supplied in predetermined proportions, helping the installer achieve the correct resin chemistry on site without estimating mixing ratios.

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This approach allows the properties of the finished binder to be engineered specifically for HFS rather than simply adapting a conventional coating or adhesive for road use.

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Once mixed and applied, the polyurethane binder provides the foundation into which the high-friction aggregate is broadcast, creating a composite surface in which the resin provides adhesion and structural integrity while the aggregate provides the critical microtexture required for tyre grip.

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Calcined Bauxite – Creating the High-Friction Surface

The aggregate is every bit as important as the resin.

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High Friction Surfacing typically uses exceptionally hard calcined bauxite, commonly with a nominal grading of around 1–3 mm. The aggregate needs to withstand extremely high localised contact pressures without rapidly polishing or losing the sharp surface characteristics responsible for its skid resistance.

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With a cold-applied system, the aggregate is broadcast onto the freshly applied resin. Once the binder has cured, excess unbonded aggregate is removed, leaving a dense layer of firmly bonded high-friction particles.

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This combination creates the characteristic aggressive surface texture that distinguishes HFS from ordinary road surfacing.

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BBA HAPAS Certified

A particularly important feature of StarPolymers HFS is its BBA HAPAS certification.

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The BBA Highway Authorities Product Approval Scheme (HAPAS) provides independent assessment and certification for specialist highway products, including High Friction Surfacing systems.

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HAPAS was launched in 1995 and has become an important part of the UK highway product-approval framework. The certification process can involve laboratory and field assessment, manufacturing audits, installation assessment and ongoing post-certification surveillance.

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For High Friction Surfacing specifically, the BBA also requires approved installers to be used and regularly inspected under a separate installer scheme.

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This distinction is important: HAPAS certification is not simply a laboratory test of a sample of resin. It provides independent assessment of the HFS system for its intended highway application.

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Designed for Critical Locations

High Friction Surfacing is not simply decorative coloured road surfacing. Its primary purpose is road safety.

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It is principally specified where additional skid resistance is justified by the risk and demands of the location, including:

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• Approaches to pedestrian crossings

• Traffic-light controlled junctions

• Roundabouts

• Sharp or hazardous bends

• Steep gradients

• High-risk junctions

• Areas experiencing severe braking

• Accident-sensitive locations

• Selected motorway and trunk-road locations

• Other areas requiring exceptionally high skid resistance

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Current highway-authority guidance continues to specify cold-applied BBA HAPAS HFS for high-risk locations such as approaches to signal-controlled junctions, roundabouts and pedestrian crossings.

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The Evolution of High Friction Surfacing

The history of HFS can therefore be viewed as a continuing development in binder technology:

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Early High-Friction Treatments → Hot-Applied Thermoplastic → Cold-Applied Epoxy → MMA / Fast-Cure Systems → Advanced Polyurethane HFS

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Each generation has attempted to retain the fundamental safety benefit of high-friction aggregate while improving the way in which that aggregate is bonded to the road.

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With StarPolymers HFS, modern three-component polyurethane chemistry combines the advantages of cold application with the toughness, adhesion and flexibility required for demanding highway environments — backed by the independent assurance of BBA HAPAS certification.

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High Performance Without the Heat

For modern highway authorities, contractors and specifiers, HFS performance is about considerably more than initial skid resistance. The system needs to bond reliably to the substrate, retain its aggregate under severe traffic stresses, withstand environmental exposure and deliver consistent performance throughout its service life.

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StarPolymers HFS has been developed around these requirements.

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Its cold-applied, three-component polyurethane technology provides a modern alternative to older hot-applied, epoxy and MMA technologies, eliminating the need to heat the binder to thermoplastic application temperatures while delivering the high-performance characteristics expected from a specialist highway surfacing system.

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Combined with carefully specified high-friction aggregate and BBA HAPAS certification, StarPolymers HFS represents the continuing evolution of high-friction road surfacing — bringing modern polyurethane chemistry to one of the most safety-critical surfaces on the highway.