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FHWA Highway Safety Programs

Case Studies and Noteworthy Practices

Case Studies

Every Day Counts (EDC) Initiative: City of Bellevue, Washington State
The Federal Highway Administration's Every Day Counts (EDC) initiative identified HFST as an innovation that enhances roadway safety and, as such, established an aggressive program to rapidly accelerate HFST deployment and adoption. While most applications of HFST occur at curves, intersections can also benefit from HFST. The treatment provides increased pavement friction which helps vehicles overcome safety issues inherent to intersections, such as a lack of adequate stopping sight distance and the need for additional braking distance at downgrade approaches. In October 2004, the City of Bellevue in Washington State installed the HFST 'Tyre-grip' on a downgrade intersection approach. Previous countermeasures, including large flashing warning signs at the bottom of the grade, additional road markers, new street lights, and raised pavement buttons, installed at the location did not achieve the desired results. After applying HFST, crashes at this intersection dropped 78 percent and costs associated with crashes declined by 83 percent.

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Pennsylvania Department of Transportation
As a solution to safety issues experienced on a problematic curve, the Pennsylvania Department of Transportation (PennDOT) installed HFST for the first time in June 2007. The treatment was approximately 800 feet in length and achieved the safety results the DOT sought. In contrast to results after previous countermeasures were deployed, the location experienced no wet pavement crashes in the eight years after the HFST installation. Results from this implementation encouraged PennDOT to install HFST at more locations, to a total of 19 locations in 2013, 65 in 2014, and to 150 by the end of 2015.

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Iowa Department of Transportation
In June 2012, Iowa Department of Transportation (IDOT) installed their introductory HFST application on a high crash risk bridge that accommodates large traffic volumes in an urban area. Road safety audits at the location, where 54 crashes occurred between 2008 and 2012, indicated skid numbers in the 30s and 40s prior to the installation. Immediately after installation, the friction values jumped to the 90s and low 100s and remained at this level for several months. After one year, IDOT measured friction values in the range of the 80s to low 100s.Within the one year following the HFST installation; the location experienced 4 crashes, only one involving an injury. The application received positive feedback, brought public recognition to the agency for solving a major safety concern, and earned the support of agency staff.

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South Carolina Department of Transportation
A one-mile section of US 25 in Greenville County, SC experienced multiple problems such as drainage, speeding, inadequate superelevation and sight distance constraints that lead to safety issues at this stretch of highways. Various low-cost safety countermeasures were added along US 25 resulting in only minimal safety improvement. In 2008, a high friction surface treatment was applied to this curvy section of US 25. A before and after study revealed significant safety benefits, with a 68 percent reduction in wet crashes and a 56 percent reduction in total crashes.

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California Department of Transportation
California DOT (Caltrans) has planned or installed high friction surface treatments (HFST) at 139 locations with roadway departure crashes. One of the locations, a horizontal curve within the Redwood National Parks' limits, experienced high frequencies of wet crashes and total and severe crash compared to other similar statewide facilities. In summer of 2012, HFST was selected over other more costly improvements due to its minimal impact on the environment, its short construction duration and its cost effectiveness. Caltrans is unaware of any crashes at this location since the HFST implementation.

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Kentucky Transportation Cabinet
The Kentucky Transportation Cabinet (KYTC) installed high friction surface treatments (HFST) at 32 locations with a history of wet roadway departure crashes, yielding significant safety benefits. One of the locations, in Oldham County on KY Route 22, had 59 total crashes from 8/1/07 thru 8/1/09 with 1 Fatal and 23 Injury crashes. After the installation of HFST in 2011, the site has experienced only 2 crashes as of 12/31/2014.

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Florida Department of Transportation
The Florida DOT (FDOT) treated a curved freeway ramp with Tyregrip®, a high-friction material consisting of a highly modified exothermic epoxy resin, dressed with calcinated bauxite, and a Polish Stone Value above 70 percent. This treatment proved effective at increasing the skid resistance value from 35 to 104. While the FDOT application was on a freeway ramp, the material may also be applicable to a higher volume curve with a higher than normal number of wet pavement crashes. The treatment type and product example provided above does not imply validation or endorsement by the FHWA Office of Safety. Several products and materials are available and should be considered to improve pavement friction.

New York State Department of Transportation
The New York State DOT (NYSDOT) implemented a program to identify sites statewide with a low skid resistance and treat them with overlays as part of their maintenance program. A site is eligible for treatment if its 2-year wet accident proportion is 50 percent higher than the average wet crash proportion for roads in the same county. Between 1995 and 1997, NYSDOT treated 36 sites, which reduced the annually recurring wet road crashes by more than 800. These results, and others throughout the State, reinforce that treating wet-road crash locations can reduce this type of crashes by 50 percent and reduce total crashes by 20 percent.

Noteworthy Practices

Systemic Installations of High Friction Surface Treatments on Small Curves in Kentucky
The Kentucky Transportation Cabinet (KYTC) had vast experience installing HFST on long and large radii curves but had yet to install small HFST applications and wanted to test its viability to be introduced at curves on the minor road system. From 2009 through 2012, KYTC installed 15 small – less than 800 square yards – HFST applications on State routes and recognized that the same benefits HFST afforded at long or large radii curves could be extended to the minor system on smaller curves. The agency bundled small installations in regional proximity into a single project for the bidding process, maximizing benefits while minimizing costs. At the 15 sites where small HFST applications were installed, KYTC noted a greater than 70 percent crash reduction overall.

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Systemic Applications of High Friction Surface Treatments in Tennessee
Up to 2011, the Tennessee Department of Transportation (TDOT) had implemented HFST at ten locations statewide, primarily for lengthening bridge lifecycles, and were interested in widespread deployment of the treatment as a safety improvement. TDOT used a data-driven procedure to select sites where HFST could effectively improve safety. Since 2011, TDOT has completed approximately 50 HFST projects and approximately 60 locations were selected for HFST applications in 2015. TDOT's systemic HFST implementation has impacted local agencies; several have expressed a desire to try HFST and contacted TDOT for guidance and information.

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Texas Department of Transportation's Methodology for Selecting Curves to Receive HFST and Other Safety Treatments
The Texas Department of Transportation (TxDOT) explored ways to improve horizontal curve safety by maximizing an investment's benefit and minimizing the need for additional improvements. TxDOT, in conjunction with the Texas A&M Transportation Institute (TTI), developed the Texas Curve Margin of Safety (TCMS), a tool to assess the "margin of safety" – friction demand subtracted from friction supply – for a particular horizontal curve. The tool computes and compares the margins of safety that can be achieved through three safety improvements: high friction surface treatments (HFST), superelevation corrections, and curve realignment, enabling agencies to foresee the benefits of HFST and other horizontal curve safety improvements before their application. The tool also helps identify the critical points of a curve that need treatment by identifying the margin of safety at the PC, midpoint, and PT.

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High Frictions Surface Treatment Applications by Thurston County, Washington
From 2006 to 2010, Thurston County, Washington experienced 177 fatal and serious injury crashes on the county's road network, not concentrated in specific locations, and about 70 percent in rural areas. After deploying many low-cost countermeasures and not achieving significant results, the County engaged in examining the use of HFST. Thurston County received HFST demonstration site funding through FHWA, and trained their staff in installing HFST. The County utilized the FHWA's Systemic Safety Tool to perform a system-wide safety review on county roads. This practice details the County's activities and achievements with respect to HFST installations and use of the Systemic Safety Tool.

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High Friction Surface Treatment Site Selection using Curve Safety Assessment Device
RwD crashes remain a major emphasis area for Georgia. To address this crash type, one of the solutions Georgia Department of Transportation (GDOT) investigated and implemented is installing high friction surface treatment (HFST) at curves where roadway departure crashes have the greatest likelihood of occurring. In order to deploy the HFST treatments more efficiently and minimize the initial construction cost, GDOT tested a new approach using a market-ready curve safety assessment device that utilizes an electronic ball bank indicator traditionally used for setting safe speeds in curves. The ultimate goal is to deploy HFST more strategically and save lives.

Noteworthy Practices: HFST Institutionalized at PennDOT
HFST is a safety countermeasure intended to restore and maintain pavement friction in wet and dry conditions to reduce crashes. This treatment is especially effective where there is a history of wet-pavement crashes. In Pennsylvania, over 50% of the fatal and serious injury crashes involve a lane departure, and intersection crashes account for 21% of the annual fatalities and 30% of serious injuries with slippery and wet roads conditions often contribute to many of the fatal and serious injury crashes. This noteworthy practice highlight PennDOT's effort in reducing wet-pavement crashes at curves and intersections throughout the Commonwealth by installing high friction surface treatments (HFSTs) at strategic locations.

Noteworthy Practice for South Dakota - HFST for Winter Road Conditions
HFST is a safety countermeasure intended to restore and maintain pavement friction in wet and dry conditions to reduce crashes and is especially effective where there is a history of wet-pavement crashes. While investigating lane departure crashes (RwD), the South Dakota Department of Transportation (SDDOT) found RwD crashes were five times more likely to involve winter road conditions than wet road conditions. In addition, one-third of the lane departure crashes occurred on horizontal curves, even though horizontal curves account for less than 10% of the system. This noteworthy practice showcases how SDDOT experiment HFST to combat winter road conditions and now has adopted HFST as one of the safety countermeasures in their toolbox to reduce winter road related crashes

Last updated: Monday, December 6, 2021