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FHWA Home / Safety / Intersection / Low-Cost Safety Enhancements for Stop-Controlled and Signalized Intersections

Low-Cost Safety Enhancements for Stop-Controlled and Signalized Intersections

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5. High-Friction Surfaces

Crash Problem

Crashes that occur when the pavement is wet on approaches with speed limits of 45 mph or more may be attributed to increased stopping distances due to low skid numbers and/or severe rutting in the wheel paths that might induce hydroplaning.

Countermeasures

The low-cost countermeasure for intersections with higher frequencies of wet pavement crashes and above average wet/total crash rates include increasing the friction characteristics on intersection approaches which have low skid numbers and eliminating any severe wheel path rutting.

One way transportation officials can increase pavement friction beyond what is attainable through traditional techniques is by using new high-friction surfacing systems. These systems are a combination of resins and polymers (usually urethane, silicon, or epoxy) and a binder topped with a natural or synthetic hard aggregate. Microtexture, macrotexture, and the durability of that texture distinguish these overlays from standard asphalt and concrete pavement surfaces. High-friction surfacing systems typically use much smaller and harder aggregates, such as calcined bauxite, slag, or other synthetic aggregates. These aggregates are generally less than 6.0 mm (0.23 inch) in diameter and have high skid resistance. The small and hard aggregate makes the overlay much more resistant to wear and polishing. The resin or polymer binder combination locks the aggregate firmly in place, creating an extremely rough, hard, durable surface capable of withstanding everyday roadway demands such as heavy braking and snowplowing. The rougher texture and greater surface area increase the pavement's friction.

The length of approach to apply skid resistance surfaces is variable dependent on approach speeds, sight distance, and expected queue lengths at signalized intersections. A minimum 300 feet of approach is recommended for through high-speed approaches to stop-controlled intersections. In addition, significant wheel rutting (2 inches in depth or greater) should be eliminated before applying any skid resistant surface.

Countermeasure Crash Reduction Factors, Threshold Levels, Additional Implementation Factors, and Estimated Cost Ranges

Crash reduction factors for skid-resistant surfaces on high-speed (i.e., 45 mph or greater) intersection approaches with a high frequency and rate of wet pavement crashes and either (1) a ribbed tire skid number of 30 or less, (2) wheel path rutting of at least 2 inches in depth, or (3) both, is 50 percent of wet pavement crashes (The FHWA Toolbox of Countermeasures and Their Potential Effectiveness to Make Intersections Safer).

Typical threshold crash levels for considering friction countermeasures on high-speed approaches to intersections are provided in Table 5.

Table 5: Crash Reduction Factors, Typical Crash Thresholds, Additional Application Factors, and Estimated Implementation Cost Ranges for Skid Resistance Countermeasures at Intersections with High Rates of Low-Friction Crashes
Countermeasure Crash Reduction Factor Typical Urban Crash Threshold Typical Rural Crash Threshold Additional Intersection Concern Implementation Cost Range per Intersection
Skid resistance surface 50% ( wet pavement crashes only) 8 wet pavement crashes in 5 years, a wet /total crash ratio above the statewide average wet/total crashes for intersections 8 wet pavement crashes in 5 years, a wet /total crash ratio above the statewide average wet/total crashes for intersections High-speed approaches (45mph or greater) and a ribbed tire skid number of about 30 or less. $20,000 to $50,000
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Page last modified on September 4, 2014.
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Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000