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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation
FHWA Highway Safety Programs

SECTION 6: Contracting and Constructing HFST

SECTION 6: Contracting and Constructing HFST

As noted above, HFST is a spot treatment that is applied to an existing roadway surface that increases the surface friction characteristics, allowing for better traction. This application consists of a binder resin system combined with polish- and abrasion-resistant aggregates. Different aggregate and binder resin system materials are available to use when applying an HFST. The following paragraphs briefly identify and explain the contracting process that was used and the materials selected for use by KYTC.

6.1 Contracting Process

At the onset of using HFST, KYTC executed a "Master Agreement" contract (i.e., "on-call" contract) with one HFST contractor in 2010. KYTC elected to adopt this method to enhance the probability for success by contracting with what essentially worked as an incentive: if the contractor performed well and was cooperative, then future work could be expected. As a result, KYTC realized the benefits as desired—both KYTC and the contractor learned in a cooperative manner how to develop and execute an effective HFST program. When issues did arise, the contractor remedied them on site or repaired the area quickly. Upon expiration of the Master Agreement, KYTC now contracts for HFST installations in a competitive regional area contracting method. The regional area contracts generally cover one construction season. Based on KYTC's experiences from the original Master Agreement, current specifications have been enhanced. To date, two installations were removed and replaced shortly after placement by the contractor due to construction-related concerns that were recognized during application. In addition, three other locations have required spot repairs. A lesson learned from the initial HFST experiences with the Master Agreement contract was it required centerline and edge line striping to be preserved (HFST is not placed over the striping) to reduce costs. New contracts will generally include HFST placement over the entire lane width and new striping.

6.2 Construction

To date all HFST installations have included a two-part epoxy binder with calcined bauxite aggregate, although KYTC is assessing other binder materials for future applications. To date, all HFSTs have been placed on dense graded asphalt mixes. Some lessons learned about construction efforts include the following:

  • Aggregate shedding does occur, and the specifications need to require sweeping both immediately after installation and 3 days after installation.
  • The inspector needs to clearly identify the application starting and stopping points for HFST application (for horizontal curves - generally 50-100' before point of curvature (beginning of curve) and 50-100' after point of tangency (end of curve) to try and capture some initial braking area.
  • If not covering up centerline or edge line striping with HFST, the inspector needs to ensure HFST is placed adjacent to the stripe.