Effects of the Installation Angle of Raised Pavement Markers on a Horizontal Curve Section on the Line of Sight Induction Performance

Different installation angles of raised pavement markers (RPMs) correspond to different incident angles of light, which affects the retroreflective performance of the RPMs. This paper explores how adjustments to the installation angle of the RPMs on a horizontal curve section affect a driver’s line of sight induction. The conditions under which RPMs achieve the optimal effect of retroreflection are confirmed, and a driver’s visual range at night is analyzed. The incident angle of light and the installation angle of RPMs are calculated when the optimal effect of retroreflection is achieved and the RPMs are installed along the radial direction (normal conditions). The differences in incident angles are compared. The results show that the differences in the incident angle under the two installment modes decrease as the radius increases, with a maximum value of 5.9 degrees. The improvement of the retroreflection with variations in the incident angle is analyzed using the STT-201A RPM measuring instrument. When the incident angle is decreased by 5.9 degrees and the observed angle is less than 2 degrees, the average increase in the coefficient of the retroreflection is only 12.6%, indicating that the improvement of the retroreflection is not obvious. Therefore, a driver’s perception of road alignment cannot be significantly improved by adjusting the installation angle of RPMs. Considering the complexity of the construction of a project, the installation angle should not be changed under normal conditions; namely, the RPMs should still be installed along the radial direction.