In phase I, the contractor performed a literature review on pavement friction and macro-texture and safety. They wrote a report on theoretical vehicle, tire, and pavement interactions as they relate to skid crashes in order to recommend the best equipment to measure friction and macro-texture. In phase III, the contractor will use the recommended equipment (purchased by the Federal Highway Administration) to test about 700 miles in several friction demand categories, in four States, to develop Pavement Friction Thresholds and Management Programs.
(1) Perform a literature review, and establish theoretical relationships for tire-pavement interactions; in order to recommend the best piece of Continuous Friction Measurement Equipment (CFME) for developing friction thresholds for maintenance intervention
(2) Perform friction tests using the best CFME (on several friction demand categories in at least four States) to establish threshold levels for friction and macro-texture, based on the procedures in the 2010 AASHTO Guide for Pavement Friction and possibly newly developed statistical methods if warranted
(3) Assist these four State DOTs to develop "Pavement Friction Management Programs"
(4) Develop training materials to document the new procedures.
The literature review and theoretical relationships reports found that a friction tester operating at about 38 % slip was the optimum in terms of duplicating the current locked wheel devices (at 100 % slip,) i.e. sensitive to the pavement, versus operating at in the range of the peak frictions (at 10 to 20 % slip) and zones where the tires dominate. Furthermore a CFME known as the Sideways Coefficient Routine Investigatory Machine (SCRIM) developed and currently manufactured in the UK, was identified as the best, because by running the tire at a 20 degree angle they create 38 % slip without applying any type of mechanical braking system to the test wheel. The SCRIM also has a track history of testing at least 150 miles per day.