USA Banner
  U.S. flag
              An official website of the United States government Here's how you knowOfficial US Government Icon
              **Official websites use .gov**A **.gov** website belongs to an official government organization in the United States.
            Secure Site Icon
              **Secure .gov websites use HTTPS**
                  A **lock** ( A locked padlock ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites. 
 U.S. Department of Transportation Icon United States Department of Transportation
 Search DOT
            Search
                    About FHWAFHWA Organization
                Headquarters Offices
                Field Offices
                Strategic Plan
                Business Opportunities
                Staff Directories
                Careers
                Highway History
                Contact UsProgramsAcquisition Management
                Civil Rights
                Federal Lands Highway
                Infrastructure
                Innovative Program Delivery
                Operations
                Planning, Environment, and Realty
                Policy
                Research, Development, and Technology
                Safety
                Browse by TopicsResourcesCore Highway Topics
                Federal Aid Essentials
                Automation
                Complete Streets
                Laws and Regulations
                Policy & Guidance Center
                Section 508
                Publications and Statistics
                Professional Development
                National Highway Institute
                Resource Center
                Accessibility Resource Library
                FHWA Research LibraryNewsroomPress Releases
                Speeches & Testimony
                Photos
                Videos
                Media ContactsMenu FHWA Highway Safety Programs Home
                        High Friction Surface Treatment Curve Selection and Installation Guide May 2016


            
            In This Section
        Pavement Friction
                Friction Management
                Continuous Pavement Friction Measurement (CPFM)
                Traditional Friction Treatments
                High Friction Surface Treatment
                Case Studies and Noteworthy Practices
                FAQs, Links, and Other Resources
                
                2. Step 2: Conduct Field Verification and Design
Field verification is an important step in determining whether HFST could be implemented, and if implemented, the limits of the HFST installation. Below is a check list of items that may be considered during a field review.

Select an Appropriate Timeframe. Consider scheduling field reviews to correlate with the primary conditions of collision patterns: time of day, day of week, season (e.g., winter, summer), pavement conditions (e.g., wet, dry), light conditions (e.g., dark, daylight), etc.
	Physically Locate Crashes. Bring a populated crash report diagram so that crashes within the curve can be easily located and studied during the field visit. Having a better understanding of crash contributing factors and location within the curve can help determine whether HFST is a viable solution and identify the limits of implementation.
	Record Roadway and Traffic Characteristics. Drive through the location several times to observe roadway and traffic characteristics, driver responses, signs, signals, and pavement markings. Observe drivers to determine behavior at the location. Take photo and/or videos and maintain a log of all photos and videos taken: location, direction, date and time of photo/video, photographer's name, etc. When possible, take a series of panoramic photos. Measure, document, and confirm a variety of data such as:
	Presence of skid marks or trees missing bark where vehicles have made impact within the curve;
		Presence and condition of previous low-cost countermeasures (e.g., signing, pavement markings);
		Damage to roadside barriers;
		Superelevation;
		Speed advisory measurements;
		Point of Curvature (PC) and Point of Tangent (PT ) of the horizontal curve;
		Horizontal and vertical sight distances;
		Intersections near or within the curve;
		Whether any of the "curve-relate" crashes are incorrectly categorized and may actually be intersection-related;
		Heavy vehicle use (especially where vehicles frequently use winter tire chains); and
		Speed differentials between the advisory speed and the posted speed limit.
	Determine HFST Start and End Points. Identify exact limits of the application if HFST is chosen as a safety countermeasure. Typically, HFST is installed at the point where vehicles start to brake. Brake lights are a good indication of where treatment could start, as the intention is to slow down the drivers as they are going into the curve. Many agencies end their treatment at the PT.17 The Texas Transportation Institute published a paper that provides further recommendations on how to select start and end points for HFST installation.18
	Conduct a Friction Test. Lower friction values have been shown to increase crash frequency. Typical means to determine friction include the British Pendulum Test (BPT ), the Dynamic Friction Tester (DFT ), the Griptester, and the Locked Wheel Skid Trailer.19 While agencies set different thresholds for satisfactory pavement friction, it is generally accepted practice to focus on pavement sections where skid numbers are below 30.
	Check Pavement Condition. If not already known, collect a pavement core sample to determine the pavement's composition, age, and quality. Also, conduct a visual inspection and record any defects in the pavement that will need to be repaired prior to HFST installation (e.g., cracks, pot holes, unstable joints, etc.). A pavement condition rating of "Good" or better is needed prior to placing HFST.20
	Screening Sample Questions. These questions may be considered while conducting a field review. The answers to some may indicate that HFST is not the best solution. Due to the site-specific nature of some of the questions, they cannot be applied universally.
	Are the collisions related to physical conditions of the location?
		Are existing signs, delineation, and pavement markings accomplishing their purpose? (I.e., Are there too few or in poor shape? Are they visible?)
		Are there any specific traffic movements to be prohibited or favored?
		Is special nighttime enhancement needed? Is existing lighting satisfactory? Are existing signs and delineation visible and retro-reflective at night?
		Are selective enforcement or maintenance procedures needed?
		Is parking contributing to collisions? Is sight distance impaired by the parking?
		Are there adequate advance guide signs so that motorists may choose proper lanes and directions well in advance of need?17 FHWA's High Friction Surface Treatments Frequently Asked Questions. Publication No. FHWA-CAI-14-019. [ Return to note 17. ]

18 B. Brimley and P. Carlson, Using High Friction Surface Treatments to Improve Safety at Horizontal Curves. July 2012. Available at: http://d2dtl5nnlpfr0r.cloudfront.net/tti.tamu.edu/documents/TTI-2012-8.pdf. [ Return to note 18. ]

19 American Traffic Safety Services Association, *Safety Opportunities in High Friction Surfacing*. February 2013. [ Return to note 19. ]

20 Oregon Department of Transportation, *GFP Pavement Condition Rating Manual*. July 2010. Available at: http://www.oregon.gov/odot/hwy/construction/docs/pavement/gfp_manual.pdf. [ Return to note 20. ]
      
  Book traversal links for 2. Step 2: Conduct Field Verification and Design
      ‹ 1. Step 1: Identify Candidate Curves for HFST
                    Up
                    3. Step 3: Select Aggregate and Binder Materials ›
                
                Book:High Friction Surface Treatment Curve Selection and Installation Guide May 2016
              1. Step 1: Identify Candidate Curves for HFST
                2. Step 2: Conduct Field Verification and Design
                3. Step 3: Select Aggregate and Binder Materials
                4. Step 4: Determine Application Method and Develop Specifications
                5. Step 5: Estimate Costs and Identify Funding
                6. Conclusion
                Appendix A – HFST Curve Identification Summary
                Appendix B – Other HFST Potential Locations and Uses U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

202-366-4000Subscribe to email updates
                    About
  

        
              About FHWA
                Careers
                Org Chart
                Staff Directories
                Work with UsPrograms
  

        
              Acquisition Management
                Civil Rights
                Federal Lands Highway
                Infrastructure
                Innovative Program Delivery
                Operations
                Planning, Environment, and Realty
                Policy
                Research, Development, and Technology
                SafetyPolicies, Rights, Legal
  

        
              About DOT
                Accessibility
                Budget and Performance
                Civil Rights
                FOIA
                Information Quality
                No FEAR Act
                Office of Inspector General
                Privacy Policy
                USA.gov
                Web Policies and Notices
                Web StandardsNews & Events
  

        
              Newsroom
                Press Releases
                Speeches & Testimony
                Media Contacts
                Connect with Us