Proper tire–pavement interaction is essential for the safety of motorists. Pavement surface texture is a major contributing factor to tire–pavement friction. This study performed a series of statistical analyses of field-measured friction and texture data to find the texture–friction correlation. Three test sections with different pavement types were selected within the state of Texas. Data were collected at three locations in the right wheel path and three locations in the center of the lane for each test section. To measure the texture data, the researchers used the circular track meter (CTM) and a prototype measurement device developed in-house and consisting of a line laser scanner (LLS). Friction measurements were obtained with the dynamic friction tester (DFT) and Grip-Tester. The mean profile depth (MPD) was calculated by using the measured texture data. The relationship between the MPD values and the friction numbers obtained from the Grip-Tester and DFT was investigated at speeds of 50 and 70 km/h (31.1 and 43.5 mph). The repeatability and reliability of both the developed LLS prototype and the Grip-Tester were also evaluated, as well as the effect of test speed on friction measurement. The results indicated a strong positive correlation between the texture and friction data. In addition, the developed LLS prototype was able to scan the pavement surface texture more reliably and precisely than the CTM in terms of vertical and horizontal resolution. The Grip-Tester showed promising results compared with the DFT with regards to the friction measurement.
The Texas Department of Transportation (DOT) ride standard specifies two devices for measuring ride quality on pavement projects: the 10-ft (3-m) straightedge and the inertial profiler. According to this specification, inertial profilers measure the ride quality on projects longer than 2,500 ft (762 m). The 10-ft straightedge must be used to survey roughness for projects of less than 2,500 ft. A study was conducted to identify the potential issues associated with the use of inertial profilers and the international roughness index (IRI) algorithm on short projects. A literature review was performed to collect required information about the inertial profiler operation and the IRI algorithm. A field experiment was conducted with an inertial profiler certified by the Texas DOT. The collected data were analyzed to investigate the effect of profiling speed and segment length. The results indicate that inertial profilers can be used to collect profile data on short segments of less than 2,500 ft, but the IRI algorithm should be used on projects longer than 528 ft (161 m), below which the variation between IRI results increases significantly.
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