High friction surface treatment: how extra pavement grip helps drivers stay on the road
How HFST adds grip at curves and ramps, and what road owners should check first
Safety Behind the Wheel Foundation built this guide from Federal Highway Administration (FHWA) guidance, technical advisories, case studies and research on pavement friction, along with peer reviewed studies. Every source is listed at the end.
What high friction surface treatment is
Every time you brake, steer or speed up, your tires lean on friction. Friction is the grip between rubber and pavement. When a road offers too little grip, tires slide and the driver loses control. These are called skid related collisions.
HFST adds grip to a short stretch of road. A crew spreads a thin coat of resin over the pavement. Resin works like a strong glue. The crew then drops tiny, hard stones onto it. The stones are about one to three millimeters across [2]. FHWA names calcined bauxite, a hard, heat treated mineral, as the stone that has given the best results [1].
The finished layer is thin, usually under a quarter inch [4]. FHWA says the goal is to restore or keep friction at places that already have, or could have, high crash rates [5]. Its guide says HFST can raise the grip of an existing surface by two to three times or more, and shorten stopping distance by 25 to 30 percent [2].
HFST is a pavement treatment, not a sign or a signal. Think of it as one tool for one problem: too little grip where drivers need a lot.
Why curves and braking areas need extra grip
In a curve, your tires must push the car sideways to hold its path. That takes grip. FHWA calls the grip a maneuver needs “friction demand.” Demand rises as speed goes up. It also rises as the curve gets tighter or has less banking [2]. Banking is the tilt of the road toward the inside of the curve.
If the road cannot supply enough grip, the car slides wide. It may leave the road or cross into oncoming traffic. This is called a roadway departure. FHWA says roadway departures caused an average of 19,158 deaths a year from 2016 to 2018, or 51 percent of all traffic deaths in the country [6].
Curves carry a big share of that risk. FHWA reported that in 2015, 23 percent of fatal collisions happened on horizontal curves, though curves make up only 5 percent of roadways [7]. A newer FHWA page says more than 25 percent of fatal collisions are linked to a curve, and most are roadway departures [8].
Water makes it worse. FHWA calls wet pavement a major factor in roadway departure crashes. It says research by the National Transportation Safety Board and FHWA indicates that about 70 percent of wet pavement collisions can be prevented or lessened by better friction [7].
Peer reviewed work points the same way. A study of rural two lane highways in Italy linked higher friction to fewer collisions, especially where wet, run off road or nighttime collisions were common [9]. For the driver’s side of this problem, see our article on roadway departure safety and recovery.
Where HFST is used and who decides
FHWA lists the places where HFST fits. They include horizontal curves, interchange ramps, intersection approaches and crosswalk approaches. They also include spots with a history of rear end, failure to yield, wet weather or red light running collisions [1]. Some are braking areas, where drivers must slow or stop fast, such as steep downhill grades.
The road owner decides. That is a state transportation agency for most highways, and a county or city for local streets. On a campus or private road, it is the property owner. FHWA’s technical advisory on pavement friction is guidance for state and local highway agencies [11].
FHWA describes the Highway Safety Improvement Program as a federal program to cut deaths and serious injuries on all public roads, including roads that states do not own. It says the program requires a data driven approach [10]. Safety Behind the Wheel Foundation encourages every road owner to take that approach when choosing sites.
Only the owner or its hired contractor may change a public road’s surface. Residents, businesses and clubs should never apply a coating or grit to one. Campuses and private owners face the same physics. They should hire a pavement or traffic engineer first, then a qualified installer.
How a site is chosen
FHWA says a friction program has three aims. New pavement should have lasting, adequate friction. Sections with high friction related crash rates should be found and fixed. Money should go where it prevents the most collisions [11]. A site review usually follows these steps.
- Sort the crash records. Separate wet from dry collisions, and note types such as run off road and rear end. FHWA’s guide says agencies look for sites with high crash counts using crash history and prediction formulas called safety performance functions [2].
- Measure friction. FHWA’s advisory lists four kinds of full scale test equipment: locked wheel, fixed slip, side force and variable slip [11]. The common locked wheel skid trailer takes samples at set spots. Continuous measurement reads friction along curves, straight sections and intersections instead [12].
- Compare demand with supply. Check speed, curve radius, banking and grade against the grip the road gives [2].
- Inspect the pavement. Look at cracking, rutting and drainage before choosing a treatment [2, 4].
- Compare treatments. FHWA lists traditional options such as thin overlays, microsurfacing and grooving beside HFST [13]. It suggests friction courses or HFST for curves with many wet weather collisions, or sharp curves with higher speeds [7].
- Set the treated length and plan follow up. FHWA’s FAQ says the usual guide is to cover a curve from start to end, but each site should be decided with data [4]. The guide also covers acceptance testing and early age monitoring after installation [2].
Not every risky curve has a crash cluster yet. Some agencies use a systemic approach. They screen a whole road network for risk features instead of waiting for collisions. FHWA’s guide describes screens such as curves tighter than 1,640 feet in radius, big gaps between the posted speed and the curve’s advisory speed, and grades above 4 percent [2].
What the evidence says
The table lists results FHWA reports. The studies measure different things, so compare them with care.
Comparison compiled by Safety Behind the Wheel Foundation
Reported results of high friction surface treatment
| Study or site | What it measured | Reported result |
|---|---|---|
| FHWA research, 2020 | Injury collisions at curves | 48% fewer [1] |
| FHWA research, 2020 | Injury collisions at ramps | 63% fewer [1] |
| NCHRP Report 617, 2008 | Total collisions at intersections | 20% fewer [1] |
| An FHWA research report | Wet and total collisions | 83% and 57% fewer [5] |
| Kentucky, 26 curves | Crashes per year | 6.2 before, 1.9 after [5] |
| South Carolina, one mile of US 25 | Wet and total collisions | 68% and 56% fewer [14] |
Treat each figure as an estimate for similar sites, not a promise for yours. Crash counts at one site rise and fall by chance. That is why careful studies compare treated sites with similar untreated ones.
Penn State researchers did that for HFST on curves of two lane highways in Pennsylvania. They matched treated curves with similar untreated curves. They found a statistically significant drop in every crash type and severity they examined [3]. FHWA’s guide says HFST can bring more benefit than low cost measures such as curve warning signs, markings and chevrons when placed at targeted sites [2].
Why the road underneath matters
HFST sticks to what lies below it. FHWA’s guide says a badly worn road will shorten the life of HFST, however well it is made. HFST does not preserve the pavement [2]. The FAQ names poor candidates: roads with widespread alligator, block or map cracking, and roads with rutting, shoving or signs of subgrade failure [4].
Preparation matters just as much. The FAQ calls surface preparation the key to success. It also says HFST should not go on asphalt or concrete less than 30 days old [4]. The guide says wide “working” cracks are usually sealed first, so water cannot seep under the treatment [2].
Moisture and weather matter too. Resin does not bond well to saturated pavement [2]. Most resins are temperature sensitive and have minimum installation temperatures, which can delay work limited to cool nighttime closures [2]. Shotblasting, a method that cleans and roughens the surface by blasting it, is required for concrete in all known state and AASHTO specifications. For asphalt, it depends on the agency [2].
Crews can apply HFST by machine or by hand. FHWA prefers machines because they avoid many problems linked to hand work [1]. Hand work suits small spots of about 200 square yards or less [4].
Limits and common mistakes
HFST solves a grip problem. A curve that hides its sharpness, a missing sign or fast traffic needs other tools. FHWA notes that most roadway departure countermeasures work at curves, and many cost little [8].
Common mistakes include:
- Treating a site before checking crash types. If collisions are not friction related, HFST may not help.
- Placing it on cracked, rutted or wet pavement.
- Skipping surface preparation or ignoring temperature limits [2, 4].
- Choosing a curve, or a treated length, with no data behind the choice [4].
- Skipping inspections after installation [4].
Drivers can make a mistake too. A treated curve gives you more margin, not permission to go faster. Ice, snow, mud and loose gravel can still cut grip. Worn tires still lengthen stopping distance. See our guide to driving in rain for tire and speed habits.
Cost, service life and upkeep
FHWA says state transportation agencies report HFST costs of $25 to $50 per square yard [5]. The FAQ says costs vary widely and have fallen on larger projects [4]. FHWA also says bundling several sites into one job can lower the price [1]. A lane 12 feet wide and 300 feet long covers 400 square yards. At $25 to $50, that is $10,000 to $20,000. That is arithmetic, not a bid.
FHWA gives its expected life as about 10 years [5]. Its guide says a well installed HFST on sound pavement should last at least 7 to 10 years, depending on traffic [2]. Weak pavement underneath can shorten that [1]. The FAQ says snowplows have had little effect, because the layer is thin and the stone wears well [4].
Upkeep means watching for early warning signs. The FAQ lists these:
- Soft, discolored patches, which can mean resin that did not cure.
- Loose or missing stone.
- Layers lifting off the road, called delamination.
- A smooth, glassy look, which can mean polished stone [4].
Owners should inspect treated areas on a schedule and fix early failures before they spread.
Hiring and buying: questions for owners
Owners usually do not buy HFST off a shelf. They hire a traffic or pavement engineering firm to study the site. An installation contractor, often approved by the agency, then buys the resin and stone from suppliers and does the work.
Private owners can use FHWA’s public guidance as a starting point, though it is written for public agencies [11].
What drivers, neighbors and local leaders can do
When you drive a treated curve, keep your usual habits. Slow down before the curve, not in it. Follow the advisory speed, and keep your phone out of reach.
If you think a curve or ramp needs a friction review, ask the road owner. Our guide to local crash data and safety maps shows how to find your area’s records. Our field guide to safer road design explains how to request an improvement.
For treated pavement that is failing, report soft patches, loose stone or smooth, glassy areas [4]. Never try to patch a public road. Call 911 if loose material or damage creates an immediate hazard.
Frequently asked questions
What is high friction surface treatment in plain words?
It is a thin layer of hard, gritty stone glued to the road with resin. The goal is to give tires more grip where drivers need it, such as a sharp curve or a ramp [1, 2].
Does HFST help in rain?
It is meant to. FHWA says wet pavement is a major factor in roadway departure crashes, and it reports large drops in wet collisions at treated sites [5, 7]. One example is a mile of US 25 in South Carolina, where wet crashes fell 68 percent [14]. Treated pavement still does not make fast driving in heavy rain safe.
Is HFST loud, and do snowplows damage it?
FHWA’s FAQ says HFST is quieter than some common surfaces, such as transversely tined concrete and chip seals. It also says snowplows have had little effect, because the layer is thin and the stone wears well [4].
How long does it last, and what does it cost?
FHWA says it lasts about 10 years and costs $25 to $50 per square yard, as reported by state agencies [5]. Its guide expects at least 7 to 10 years on sound pavement [2]. Both vary by site, traffic and climate.
Can I or my business apply HFST to a road?
Not on a public road. Only the road owner or its hired contractor may change the surface. Owners of private roads and campuses can use it, but they should hire an engineer and an experienced installer. Surface preparation and pavement condition decide whether it works [2, 4].
How do I ask my city or state to look at a dangerous curve?
Find out who owns the road. Then send the exact location and direction, plus three to five years of crash history if you have it. Say whether collisions happen wet or dry, and ask for a review of crash and friction data. FHWA says agencies combine these data to decide where friction treatments belong [1].
The bottom line
Recommendation from Safety Behind the Wheel Foundation
Safety Behind the Wheel Foundation encourages road owners to choose friction treatment sites with crash and friction data, and urges drivers to slow for curves whatever the surface. HFST can give drivers a margin where grip runs out. It works when the site is chosen with data, the pavement is in good shape and the installation follows a written specification.
You can do your part. Drive curves slowly, keep your tires in good shape, and report damaged pavement. If a curve worries you, give the road owner exact facts and ask for a data review. Leave the treatment to the people authorized to do it.
Related articles
- Roadway departure safety: curves, drop offs and how to recover safely
- Safer road design: a field guide to the safety fixes on your street
- Driving in rain: hydroplaning, standing water and flood safety
- Rural road safety: why country roads are deadlier and how to drive them
- Local crash data and safety maps: how to find and read your area's data
Sources and further reading
- 1Federal Highway Administration (FHWA). Pavement Friction Management (Proven Safety Countermeasures, FHWA-SA-21-052). Page date not shown; reviewed October 2026. Data year: crash reduction figures from FHWA research published 2020; intersection figure from NCHRP Report 617 (2008). [https://highways.dot.gov/safety/proven-safety-countermeasures/pavement-friction-management](https://highways.dot.gov/safety/proven-safety-countermeasures/pavement-friction-management) (companion fact sheet PDF with installation and cost notes: [https://highways.dot.gov/sites/fhwa.dot.gov/files/Pavement%20Friction%20Management_508.pdf](https://highways.dot.gov/sites/fhwa.dot.gov/files/Pavement%20Friction%20Management_508.pdf)) highways.dot.gov/…/Pavement%20Friction%20Management_508.pdf
- 2Federal Highway Administration (FHWA). High Friction Surface Treatment Site Selection and Installation Guide. Published October 2021. highways.dot.gov/media/11626
- 3Gayah VV, Donnell ET, Zhang P. Crash modification factors for high friction surface treatment on horizontal curves of two-lane highways: A combined propensity scores matching and empirical Bayes before-after approach. Accident Analysis and Prevention, 2024 (volume 199, article 107536; DOI 10.1016/j.aap.2024.107536). PubMed record (PMID 38447354). Data year: Pennsylvania two-lane curves; years not stated in the abstract. pubmed.ncbi.nlm.nih.gov/38447354
- 4Federal Highway Administration (FHWA). High Friction Surface Treatments – Frequently Asked Questions, 2022 Update. Published July 2022. highways.dot.gov/media/20871
- 5Federal Highway Administration (FHWA). High Friction Surface Treatments (HFST). Updated December 17, 2025. Data year: n/a (guidance); costs as reported by state DOTs, year not stated. highways.dot.gov/…/high-friction-surface-treatments-hfst
- 6Federal Highway Administration (FHWA). Roadway Departure Safety. Updated August 25, 2023. Data year: 2016 to 2018. highways.dot.gov/safety/roadway-departure-safety
- 7Federal Highway Administration (FHWA). Pavement Friction. Updated December 9, 2016. Data year: 2015 (curve share of fatal crashes). highways.dot.gov/…/pavement-friction
- 8Federal Highway Administration (FHWA). Horizontal Curve Safety. Updated August 25, 2023. Data year: not stated on the page. highways.dot.gov/…/horizontal-curve-safety
- 9Cafiso S, Montella A, D’Agostino C, Mauriello F, Galante F. Crash modification functions for pavement surface condition and geometric design indicators. Accident Analysis and Prevention, 2020 (volume 149, article 105887; DOI 10.1016/j.aap.2020.105887). PubMed record (PMID 33246550). Data year: Italian two-lane rural highways; years not stated in the abstract. pubmed.ncbi.nlm.nih.gov/33246550
- 10Federal Highway Administration (FHWA). Highway Safety Improvement Program (HSIP). Updated October 7, 2025. highways.dot.gov/…/hsip
- 11Federal Highway Administration (FHWA). Technical Advisory – Pavements (T 5040.38): Pavement Friction Management. Issued June 17, 2010; page updated September 18, 2017. fhwa.dot.gov/pavement/t504038.cfm
- 12Federal Highway Administration (FHWA). Continuous Pavement Friction Measurement (CPFM). Updated September 14, 2023. highways.dot.gov/…/cpfm
- 13Federal Highway Administration (FHWA). Traditional Friction Treatments. Updated September 26, 2022. highways.dot.gov/…/traditional-friction-treatments
- 14Federal Highway Administration (FHWA). Case Studies and Noteworthy Practices (pavement friction). Updated December 6, 2021. Data year: varies by case study (installations from 1995 to 2014). highways.dot.gov/…/case-studies-and-noteworthy-practices
This article reflects the safety priorities of safer road design and preventing skid and curve collisions. It is general education, not legal, engineering or financial advice, and it does not replace a site review by the road owner. Guidance, costs and results change, so verify details with official sources. For your own situation, contact the state, county or city agency that owns the road. Private owners should consult a licensed pavement or traffic engineering firm. Reviewed October 2026.
Cite this article: Safety Behind the Wheel Foundation. “High friction surface treatment: how extra pavement grip helps drivers stay on the road.” drivewithcare.org, https://drivewithcare.org/high-friction-surface-treatment-guide/. Reviewed October 2026.
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