Repeatability and Reproducibility of Mobile Retroreflectivity Units for Measurement of Pavement Markings

The Florida Department of Transportation has historically used a combination of handheld devices and visual surveys to evaluate the retroreflectivity of pavement markings. However, visual surveys have the inherent limitations of operator bias, while the use of a handheld device is slow and labor intensive and presents safety hazards. Many highway agencies have recognized that a mobile retroreflectivity unit (MRU) may be a safer and more efficient alternative to the handheld retroreflectometers. Because the measurement process relies on the operator-driven instrument, a level of uncertainty is always a concern in evaluating pavement markings with the MRU. This research was aimed at assessing the precision and bias of the MRU while using the handheld retroreflectometer as a reference device. Ten 1.0-mi-long field sites were selected to include various pavement surface types and pavement marking materials (paints and thermoplastics). The results indicated that, when compared with the handheld retroreflectometers, the MRU demonstrated no statistical differences or bias at a 95% confidence level for the retroreflectivity values ranging between 200 and 800 mcd/m(2)/lux. In addition, it was determined that the retroreflectivity values from two properly conducted tests using a single MRU on the same pavement marking should not differ by more than 7.8%, and when different MRUs were used on the same pavement marking, the retroreflectivity values should not differ by more than 13.3%. This paper presents a description of the testing program, the data collection effort, and the subsequent analyses and findings.