Evaluation of Pavement Friction Performance on Interchange Ramps at Network Level

Most state highway agencies conduct inventory friction testing on mainline highways to monitor network pavement friction performance. However, no state highway agencies have been reported to monitor pavement friction performance on interchange ramps. Interchange ramps constitute a large portion of the interstate highway facilities. Great concerns have arisen nationwide due to the increasing number of accidents in the ramp areas. This paper presents an effort to evaluate pavement friction performance on interchange ramps in Indiana. It is found that the overall average posted speed is 38 mi/h on interchange ramps, which is close to the test speed of 64 km/h recommended by AASHTO for establishing pavement friction requirements. In addition, pavement friction seemed to decrease as ramp curvature decreased. In general, three tests at the entrance, midpoint, and exit can provide information sufficient to evaluate pavement friction performance on an entire ramp. The 15th percentile friction number for overall interstate mainline pavements is 30 and 29 for the selected ramps.