Longitudinal pavement markings are found on nearly all freeways and highways in the United States, and previous research has emphasized the importance of quantifying the impact of different pavement marking material types on safety. While important, quantifying safety of pavement marking and marker material types has remained elusive. This study takes a unique approach compared to previous research, and instead focuses upon quantifying the relationship between retroreflectivity and safety over time, independent of marking or marker material type. The study examined the safety effect of retroreflectivity of longitudinal pavement markings and markers over time on non-intersection locations during non-daylight (night, dawn, and dusk) conditions. In order to estimate retroreflectivity, mathematical models were developed as a function of key performance variables and applied retroactively to locations of known pavement marking and marker installation dates and materials.

The estimated retroreflectivity was then compared to the number of non-intersection, non-daylight crashes occurring over time on multilane freeways, multilane highways, and two-lane highways using an innovative analysis methodology developed for this study. In summary, this study found that there is no safety benefit of higher retroreflectivity for longitudinal markings on non-intersection locations during non-daylight conditions for roads that are maintained at the level implemented in California's state highways. California's level of maintenance appears to be frequent with pavement markings being installed on higher volume highways up to three times a year with waterborne paint, or every two years with thermoplastic markings. The findings of this research study allow agencies to recognize that resources to increase the retroreflectivity of longitudinal markings, beyond normal maintenance activities, will not be cost-effective and that those resources could instead be allocated towards other safety measures.