Suggestions from Research Literature

Human factors research investigating the retroreflectivity needs of drivers includes three main types of evaluations: subjective evaluations, objective evaluations, and visibility models:
  • Subjective Evaluations
     include studies where drivers are asked to evaluate pavement markings while they navigate through a roadway course.
  • Objective Evaluations
     include studies where drivers are asked to detect pavement markings of varying retroreflectivity levels while driving through a course.
  • Visibility Models
     are computer software packages used to predict necessary levels of retroreflectivity based on actual data.
The research literature contains numerous recommendations for minimum levels of retroreflectivity. When measured at 30 meter geometry, these minimum levels found in the literature fall in the approximate range of 80–620 mcd/m
2
/lx for high-speed roadways in a dark environment, with the range of 100–150 mcd/m
2
/lx encompassing most of the recommendations. Most of the subjective evaluations produced minimum values in the lower range, while the objective evaluations and modeling analyses suggested much higher minimum values. The research has aided the FHWA in development of recommended minimum in-service values for pavement marking retroreflectivity.