Visibility of New Dashed Yellow and White Center Stripes as Function of Material Retroreflectivity

Abstract

Economic and environmental concerns have raised questions about the continued use of yellow center lines on two-lane highways and yellow left-edge lines on divided highways or freeway entrance and exit ramps. The use of yellow pavement markings as a warning to indicate opposing traffic appears to be a concept that is compatible with certain human factors population stereotypes and accepted industry standards (yellow for caution), but it is unclear how well the general driver population understands the message conveyed by yellow pavement markings. Another question is how the visibility of yellow center lines or left-edge lines compares with the visibility of similar white pavement markings. The effects of color (white and yellow) and material retroreflectivity (low, medium, and high) on the end detection distance of finite-length center lines at night under automobile low-beam illumination were determined. Ten subjects were used in a field experiment (rural, automobile low-beam conditions) to obtain the end detection distances of finite-length center stripes of 0.1-m width. The data show that the end detection distances of new yellow dashed center stripes and new white dashed center stripes are about the same. The average end detection distance was 30 to 35 m for the low-retroreflectivity material and about 62 m for the high-retroreflectivity material (four- to fivefold retroreflectivity increase). It is tentatively concluded that the use of white center stripes most likely will not result in a significant increase in the end detection distance when compared with the use of similar yellow center stripes. It is also tentatively concluded that an increase in the retroreflectivity of the pavement marking materials will result in a significant and desirable increase of the visibility distance, but to provide a minimum preview time of 3.6 sec (at a vehicle speed of 90 km/hr), even higher-retroreflectivity materials than the ones used in this study will be required.