Method of Determining the Thickness and Uniformity of Application for Thermoplastic Pavement Marking Material;Final rept

摘要

A laser thickness-measurement device for measuring the thickness of thermoplastic pavement marking material (TPMM) has been successfully developed. The system has been installed onto a pushcart for easy field operation. The device is based on a laser triangulation measurement system and it uses a position sensitive device (PSD) as the detector. The hardware developed includes a laser thickness detector, mechanical scanner, angle encoder, distance encoder, global positioning system (GPS) and interface circuitry, data acquisition and control circuitry, and data display. Software functions developed include data processing, embedded computer control, data filtering and the user interface. The system operates at a sampling rate of 175 kHz, which significantly increases the accuracy and speed of the thickness measurement and provides more quantitative information for determination of the TPMM and pavement profiles. The flexible hardware design enhances the system's performance under varied pavement conditions. The high response frequency allows the system to quickly adapt to sudden changes in slope and color. Lab and field tests demonstrated that the measured thicknesses were very close to the actual thickness of the tapes measured. Measurement error on smooth pavements (asphalt and concrete) was less than 5 mils. Measurement error on grade 3 surface treatments was within 10 mils.