High Friction Surface Treatments (HFST) FAQs

The purpose of HFST is to enhance road friction in critical locations, improving vehicle handling and reducing the risk of skidding, especially in wet conditions or high-friction-demand areas.

HFST is particularly effective in locations such as local roads, high-volume intersections, interchange ramps, and segments of interstate highways. The treatment is useful for addressing site-specific issues like sharp curves and intersections with frequent crashes.

HFST sites can be selected using site-specific safety approaches that rely on crash data or systemic approaches that identify high-risk features even in the absence of crash history. Continuous pavement friction measurement (CPFM) and predictive analysis can also help identify suitable locations.

HFST is typically installed where vehicles start to brake. In curves, it is applied from the point where brake lights are visible up to the point of tangent. Installation guidelines help ensure friction is improved where needed most.

Yes, FHWA studies have developed CMFs for HFST installations at curves and ramps, showing statistically significant reductions in total, injury, wet road, and run-off-road crashes.

Loose aggregate should be removed after installation and during the initial post-installation period to avoid hazards for drivers, motorcyclists, and bicyclists. Signage may be used to alert motorists and riders to potential debris or temporary surface changes during curing.

HFST improves safety for motorcycles and bicycles by providing better traction. It has been used in bike lanes and has shown positive results in reducing motorcycle crashes.

Yes, by increasing surface friction, HFST helps prevent truck rollovers on curves and ramps where vehicle control is critical.

Studies show that HFST does not increase driving speeds. Its purpose is to provide additional friction to help vehicles stay on the road rather than encourage speeding.

HFST provides a significant safety benefit in curves where signage and markings alone are insufficient. It can reduce crashes by providing a hidden advantage through its high-friction surface, making it a cost-effective alternative to geometric road changes.

Yes, research has shown that HFST reduces improper stopping behaviour, such as crosswalk incursions at red lights, by up to 31% several months after installation.

Yes, HFST can be used in conjunction with rumble strips to provide both auditory warnings and increased traction for drivers.

HFST requires little maintenance, but periodic cleaning to remove debris, leaves, or loose aggregate may be necessary to ensure optimal performance.

There is no evidence that HFST increases tire wear in a meaningful way. Public complaints have been minimal and unverified. HFST is only applied at spot locations, making significant wear unlikely.

Yes, HFST can be removed using micromilling or diamond grinding. If removed with base pavement, it can be recycled with no negative impact on the recycled material.

The benefit-cost ratio is often high, ranging from 5:1 to 30:1, depending on the location and the type of crashes being mitigated, making it a cost-effective safety measure.

Costs are influenced by traffic control, pavement marking treatment, and labor. Using high-quality, durable materials like calcined bauxite also contributes to the cost, though it provides long-lasting results.

Though the initial cost of HFST may be higher than other treatments, its long-term safety benefits and crash reduction outcomes make it highly cost-effective when evaluated as a safety countermeasure.

HFST has a minimal environmental impact due to its quick installation process, reducing the need for long-term road closures and minimizing traffic disruption. The treatment uses durable, long-lasting materials, which means fewer replacements and less resource consumption over time. Additionally, HFST helps prevent accidents, indirectly reducing the environmental toll of crashes, such as emissions from traffic delays and vehicle recovery efforts.

HFST does not alter drainage patterns or increase impervious surface area. Its staged, lane-by-lane installation minimises pollution and congestion compared to full road closures or major construction.

Calcined bauxite is the recommended aggregate for HFST because of its high polish stone value (PSV), which ensures long-lasting friction. Other aggregates like flint and granite have been evaluated but do not perform as well as bauxite.

Chip seal is primarily a pavement preservation technique, while HFST is a safety measure. HFST provides significantly better friction in critical locations, whereas chip seals are typically used for extending pavement life and provide temporary friction improvement.

Yes, the polymer binder used in HFST is resistant to common road chemicals, including de-icing agents, unless flooded with diesel fuel or solvents.

Yes, reclaimed aggregate can be reused if it meets cleanliness and gradation standards. It should be blended with virgin material and tested before reuse.

HFST materials generally do not crack on their own. Cracks in the underlying pavement may reflect through but can be repaired using standard methods.

Yes, HFST can be applied over painted lines, but thermoplastic markings should be removed or covered before installation to ensure proper adhesion.

Double layers of HFST are commonly applied to bridge decks to provide additional water resistance and friction. This method is also used on roads exposed to snow chains or studded tires.