Safe driving in adverse conditions—whether rain, fog, or darkness—requires visible road markings. Retroreflective pavement markings that bounce light from vehicle headlights back to drivers’ eyes improve safety and prevent roadway departure crashes, but they must be maintained to ensure they remain visible over time.
Some highway agencies rely on fixed repainting schedules, while others measure retroreflectivity with handheld or mobile measurement systems to determine when pavement markings need to be repainted. A grant from the Federal Highway Administration Technology Partnerships program enabled Leetron Vision LLC of Concord, NH, to refine its prototype Mobile Retroreflectivity Unit (MRU) to improve its ability to handle various road and environmental conditions and collaborate with the Florida Department of Transportation to conduct field tests.
The MRU uses real-time laser tracking technology to measure pavement marking reflectivity at highway speeds. A new FHWA report, Advanced Methods for Mobile Retroreflectivity Measurement on Pavement Marking, explains the technology, outlines steps taken to refine the Leetron unit, and discusses results of tests using the system to collect pavement marking data. The Technology Partnerships program, part of the Highway for LIFE program to accelerate innovation use in transportation, provided grants to private industry to further develop proven, late-stage prototypes and evaluate them in real-world settings.
Refining the Prototype
The Leetron system uses a method of tracking measurements in real time that mitigates the effects of vehicle motion and variance in the road profile, one of the most challenging aspects of mobile retroreflectivity measurement. Using variable geometry technology, the system aims a laser at the center of the pavement marking and uses a feedback loop to readjust the aim point as the vehicle equipped with the unit travels at highway speeds.
“In the process of finalizing the product from a prototype, a number of refinement cycles were incorporated in the testing to ensure that the unit remained capable of handling conditions in real-world settings,” system developer Terry Lee said in the report. “Extensive road testing and refinements helped develop a robust, commercial-ready system.”
The system offers a faster measurement method than traditional systems by allowing simultaneous measurement of markings in two lanes. It also has an automatic calibration capability that minimizes downtime and maximizes data collection.
An independent evaluation conducted by the Texas A&M Transportation Institute confirmed that the Leetron system can collect accurate retroreflectivity data on a range of paving marking types under a variety of challenging conditions. The evaluation included controlled testing in a laboratory and on an airfield runway along with field testing on open roads. “The results of the comprehensive testing demonstrate Leetron Vision’s MRU using variable geometry technology is capable of accurately measuring pavement marking retroreflectivty under a broad range of realworld conditions,” the report said.