1. Portorož, Slovenia Evaluation of the International Friction Index Coefficients for Various Devices Gerardo FlintschGerardo Flintsch Center for Sustainable Transportation InfrastructureCenter for Sustainable Transportation Infrastructure DirectorDirector flintsch@vt.eduflintsch@vt.edu

2. Overview Objective Background Experimental program Results Conclusions Center for Sustainable Transportation Infrastructure

3. Acknowledgements Oscar Gonzalez & Edgar de Leon  Center for Sustainable Transportation Infrastructure, VTTI Kevin K. McGhee  Virginia Transportation Research Council Mark Swanlund  Federal Highway Administration Center for Sustainable Transportation Infrastructure

4. Objective Background Experimental program Results Conclusions Center for Sustainable Transportation Infrastructure

5. Different research efforts have studied procedures to harmonize friction measurements  PIARC Experiment to Compare and Harmonize Texture and Skid Resistance Measurements  NASA Wallops Friction Workshops Program  HERMES Experiment Center for Sustainable Transportation Infrastructure Motivation

6. To compare friction and macrotexture measurement results and determine if the previously adopted models are valid for the devices considered.  Measurements taken at the Virginia Smart Road in 2008 by the members of the Pavement Surface Properties Consortium. Center for Sustainable Transportation Infrastructure Objective

7. Background Experimental program Results Conclusions Center for Sustainable Transportation Infrastructure

8. Background: Pavement Surface Properties Consortium R esearch program focused on enhancing the level of service provided by the roadway transportation system through optimized pavement surface texture characteristics.

9. The Virginia Smart Road

10. The Virginia Smart Road Layout SM 9.5 D SUPERPAVE OGFCSMA 9.5 D Tined CRCP JRCP Ground JRCP Cargill SafeLane™ VDOT EP5LV

11. Pavement Surface Properties Consortium Current Projects 1. Annual Equipment Rodeo 2. Seasonal Monitoring 3. Evaluation of New Measurement technologies 4. Evaluation of new “High-friction” pavement technologies 5. Griptester loan program 6. Stereo Vision Texture Measuring Center for Sustainable Transportation Infrastructure

12. Objective Background Experimental program Results Conclusions Center for Sustainable Transportation Infrastructure

13. Experimental Program 24 sections  12 x 2 directions 3 Speeds 5 repetitions @ each speed 2008 Devices:  2 Locked-wheel trailers  DFTester  Griptester Center for Sustainable Transportation Infrastructure  2 CTMeters  1 laser profiler w/ macrotexture  Other …

14. Sample of Equipment Used Center for Sustainable Transportation Infrastructure

15. Experimental Section Layout

16. Objective Background Experimental program Results Conclusions Center for Sustainable Transportation Infrastructure

17. Results: Comparison Using Original Coefficients Center for Sustainable Transportation Infrastructure

18. Revised Coefficients Center for Sustainable Transportation Infrastructure

19. Adding Macrotexture Center for Sustainable Transportation Infrastructure

20. Comparison of F60 IFI Coefficients Frictio n Unit Original Coefficients (1)Revised Coefficients ABCR2R2 ABCR2R2 LWS10.04460.925-0.345 0.19580.4599-0.349 0.20300.25960.08620.796 LWS20.04460.925-0.371 0.11770.5542-0.371 0.14010.34850.08610.831 GT0.08210.9104-0.623 0.14590.6125-0.623 0.20730.33020.06080.785 LWR1-0.02280.60680.09760.78310.12830.24940.11880.7831 Center for Sustainable Transportation Infrastructure

21. “Experimental” Sp Center for Sustainable Transportation Infrastructure

22. Speed Constant Center for Sustainable Transportation Infrastructure

23. Comparison of Sp Models Devices LinealPower abR2R2 abR2R2 DFT Sp1222590.26113780.3000.2247 LWR1 Sp18.31600.0492136-0.2110.0823 LWS1 Sp20.037.10.209656.40.4690.3156 LWS2 Sp47.125.00.384870.70.7670.5609 GT48.0-2.950.334239.41.1680.4312 Center for Sustainable Transportation Infrastructure Table 4 -

24. Objective Background Experimental program Results Conclusions Center for Sustainable Transportation Infrastructure

25. Conclusions The original PIARC coefficients did not produce harmonious results for the devices and surfaces tested  the original coefficients determined during the PIARC experiment may need to be adjusted for the devices evaluated before the IFI can be implemented in the participating agencies Center for Sustainable Transportation Infrastructure

26. Conclusions (cont.) The results also suggest that that there is a better correlation of the speed gradient, Sp, with macrotexture using a power model than with the linear model used on the original IFI equations  Particularly for the measurements using smooth tires Center for Sustainable Transportation Infrastructure

27. Conclusions (cont.) Preliminary revised coefficients for the participating devices are provided based on the results on the sections tested. However, it is recommended that these values are verified on other surfaces before implementation. Center for Sustainable Transportation Infrastructure