Volume 33, Issue 5 (September 2005)
Considerations in Developing a Network Pavement Inventory Friction Test Program for a State Highway Agency
A network pavement inventory friction test program should consist of three parts: testing system calibration and performance verification, friction testing, and data management. The friction testing system must be calibrated and its performance must be verified before test seasons and whenever significant changes have occurred. Friction testing should be conducted annually on interstates. Test frequency for other routes may be reduced. Also, friction testing should be conducted consistently in the driving lane. Test intervals should be large enough for the operator to adjust test speed.
Differences exist between the friction numbers measured by smooth and ribbed tires. For grooved concrete surfaces, the difference is negligible. For others with low or medium friction, the average difference is about 17 or 12. Different surface features may result in different speed gradient curves. Seasonal variation is not significant. A minimum friction requirement of 20 to 23 was identified for the smooth tire. Friction data management is an important part for the network inventory friction test program. Geographical information system (GIS) technology can be utilized to monitor network pavement friction condition efficiently.