Evaluation of locked-wheel skid trailer and SCRIM friction measurements at NCAT test track

ABSTRACT

This study aimed to evaluate the repeatability of locked-wheel skid trailer (LWST) and sideway-force coefficient routine investigation machine (SCRIM) measurements and investigate the influences of test speed and test temperature on the friction measurements. This study selected 14 test sections from the NCAT Test Track with different surface texture and friction characteristics. The LWST and SCRIM tests were conducted at different test speeds and test times (or temperatures) on the two consecutive days. The repeatability analysis indicates that both LWST skid number (SN) and SCRIM reading (SR) measurements were most repeatable at a test speed of 50 mph and tangent section. The SN measured in the late afternoon and SR measured at noon were more repeatable than those measured at other times. This study recommended an acceptable precision of friction measurement be within 2.5 SN or 3 SR units. In addition, this study concluded that the SN and SR had a good linear correlation. The statistical regression analysis demonstrates that test speed, air temperature, pavement mean profile depth, and pavement type were significant variables affecting asphalt pavement friction. The developed regression models for SN and SR were helpful to correct the friction measurements to a reference speed or temperature.

KEYWORDS:

• Pavement friction
• lock-wheel skid trailer
• sideway-force coefficient routine investigation machine
• repeatability
• atistical regression model

Acknowledgements

The authors acknowledge the financial support by the Alabama Department of Transportation (DOT), Kentucky Transportation Cabinet, Mississippi DOT, North Carolina DOT, South Carolina DOT, and Tennessee DOT through the Southeast Superpave Center Pooled Fund Program. Special thanks are extended to Frank Bell from the Alabama DOT for coordinating the LWST test, Jason Nelson from NCAT for coordinating the operation of NCAT Test track, and the WDM team for coordinating the SCRIM test, processing SCRIM data, and providing technical guidance.

Disclosure statement

No potential conflict of interest was reported by the author(s).