Investigation of the Safety Effects of Edge and Centerline Markings on Narrow, Low-Volume Roads

About the report:

Residency and regional traffic engineering staff of the Virginia Department of Transportation (VDOT) have postulated that the use of low-cost centerline and edgeline pavement markings, applied individually or in combination, can improve safety on narrow roads until higher cost, road-widening design improvements can be programmed and implemented. Mostly narrow secondary roads would fall in this category, but narrow primary roads would also be included.

The original purpose of this study was to develop a set of guidelines for VDOT traffic engineers to use when making decisions regarding the use of edgelines and centerlines on narrow, low-volume (less than or equal to 3,000 vehicles per day) roads. These guidelines were to be developed in a two-phase process, with the initiation of the second phase depending on the results of the first phase. This report describes the Phase I study, which included examining relevant literature; gathering information from other state departments of transportation; conducting a statewide inventory of edgeline and centerline markings; and performing a cross-sectional crash analysis of narrow roads identified in the inventory as (1) not having edge and centerline markings, (2) having both edge and centerline markings, (3) having edgeline markings only, and (4) having centerline markings only.

The study found that there is much variation in the practices of state departments of transportation with regard to installing pavement markings on roads 16 to 20 ft wide. In addition, the limited analysis of crash frequency, density, rate, and safety performance found no statistical difference between segments with and without centerlines and/or edgelines. Based on the results of this Phase I study, the project was limited to one phase. Therefore, a Phase II study to develop guidelines was not considered.

The study recommends that VDOT consider (1) developing a statewide process for a pavement marking inventory; (2) asking the Office of the Attorney General of Virginia for an interpretation/opinion of the term “appropriate” in House Joint Resolution No. 243 passed in the 1994 Session of the Virginia General Assembly; and (3) evaluating data from the Virginia Tech Transportation Institute’s naturalistic driving study to determine if the data may be used to evaluate driver behavior on roads 16 to 20 ft wide with or without centerlines and/or edgelines.

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