Optical Sizing and Roundness Determination of Glass Beads Used in Traffic Markings

This digest summarizes key findings from National Cooperative Highway Research Program (NCHRP) Project 20-07, Task 243, "Development of a Test Method for Optical Sizing and Roundness Determination of Glass Beads Utilized in Traffic Markings," This digest was prepared from the project final report, which is available as NCHRP Web-Only Document 156 at http://www.trb.org. In NCHRP Project 20-07, Task 243, an interlaboratory study (ILS) was designed and conducted to (1) determine the precision and bias of both optical and traditional mechanical methods for different glass bead types (as defined in AASHTO M 247), (2) compare the precision and bias of various measurement methods, and (3) develop a practice in AASHTO standard format for the use of computerized optical methods and equipment to measure the size and roundness of glass beads used in traffic markings.