Safety Aspects of Line Markings on Two-Lane Low-Volume Narrow Roads in Virginia

Abstract

Pavement line markings are designed to provide drivers with visual clues for safe driving, and their installation is generally determined based on roadway width, traffic volume and functional classification. In general, for two-lane roadways, the Virginia Department of Transportation currently installs a centerline pavement marking on roads that have a minimum traffic count of 500 vehicles per day and a minimum width of 18 ft. This study examined the safety aspects of line markings on low-volume (3,000 vehicles per day or less) narrow (20 ft or less) roads in Virginia. Four ways of measuring safety performance were employed. Crash frequency, density, rate and safety performance functions were used for those roads under four line marking types: no lines, a centerline only, edge lines only and both lines. Based on five years (2004~2008) of crash data on 4,797 road segments in Virginia, the study found no statistical difference between the presence and absence of a centerline and/or edge lines on the low-volume narrow roads. Omitted factors, such as curvature and speeds, might have some influence on the findings. By examining the age distributions of drivers in the crashes, it is conjectured that adding line markings can plausibly be inferred to provide safety benefits for teen drivers.