A surface dressing consisting of an epoxy-resin-based binder and approximately 2 to 3 mm size calcined bauxite chippings, with the proprietary name 'shellgrip', was laid at the approach to traffic signals on trunk road A1 at Sandy, Bedfordshire in 1968. Materials of this type maintain exceptionally good resistance to skidding under intense traffic in urban (low-speed) conditions. The primary objective of this experiment was to determine whether this small size of chipping could give sufficient texture-depth to maintain good resistance to skidding at high speed. The laying operation and early life performance have already been reported. This report gives the results of sideway force coefficient, and braking force coefficient measurements made at regular intervals since 1968. At test speeds of 50 and 80 km/h the resistance to skidding is still very high after 9 years under traffic, even though the asphalt substrate is showing through in many areas where the dressing has worn away. However, at 130 km/h the resistance to skidding remained at the highest level for only 2 years in the nearside lanes, which carry the majority of commercial vehicles. Subsequently, it fell as texture depth was lost. (Author/publisher) See also IRRD abstract no 60081
Abstract