This project consisted of determining the optimal spacings for raised reflective pavement markers (rrpms) along tangent sections and on interchange ramps of interstate highways. Theoretical optimal spacings were firt determined by using photometric calculations for the tangent sections, assuming clear and slightly degraded atmospheric conditions (rain intensity of 1 in./Hr), and by using geometric calculations for the interchange ramps to determine the maximum driverviewing distance. As a result, optimal rrpm spacings of 25 and 120 ft were recommended for field evaluation for interchange ramps and tangent sections, respectively. Also included in this project was a test driver study using an instrumented vehicle to evaluate the recommended optimal rrpm spacings on dry and wet pavement in clear and slightly degraded atmospheric conditions. The tests were conducted at night on four unlit tangent sections (each 1 mi long) and on four unlit interchange ramps (each about 1, 000 ft long with a 24 degree curve) of interstate 70, east of columbus, ohio. Vehicle lateral lane position and speed maintenance were measured and analyzed for different rrpm spacings (for tangent sections at 60, 120, and 240 ft along the lane line, and no rrpms; for ramps at 12.5, 25, And 50 ft along the outer edge line, and on rrpms). On the basis of the results of this study, a maximum rrpm spacing of 120 ft for the lane line is recommended for tangent sections on interstate highways, whereas no rrpms are recommended for interchange ramps along interstate highways. This paper appeared in transportation research record no. 1149, Visibility for highway guidance and hazard detection. For covering abstract see IRRD no 817811.
Abstract