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Title:

Modern Pavement Marking Systems: Relationship Between Optics and Nighttime Visibility

Abstract:

Pavement markings are a fundamental component of the roadway safety infrastructure. Their primary functions are to provide a preview of the road geometry, aid the driver in their choice of appropriate travel lane and support the driver in maintaining the vehicle position within the lane. The majority of pavement markings are retroreflective in order to provide at least some level of nighttime visibility for the driver. A small fraction is also wet reflective to provide night visibility even under rainy and wet conditions. The FHWA is working to establish requirements for minimum maintained retroreflectivity of pavement marking on U.S. public roads. This task is complicated by the fact that conventional measurements of dry retroreflectivity do not tell the entire story with regard to pavement marking visibility. To that end, there is ongoing research within FHWA, academia, and industry to understand the relationship between the retroreflective properties of pavement markings and the level of on-road visibility they provide. A pavement marking system has three basic components ? the optics, the structure and the binder. The choice of materials and technology for each component has a significant influence on the marking's visibility at night. These same choices also impact the ability to quantify the retroreflective efficiency of the marking and to develop reliable correlations between pavement marking photometric properties and their visual performance on the road. Such correlations are necessary to support practicable minimum maintained pavement marking visibility requirements. Standardized measurements using portable pavement marking retroreflectometers are commonly assumed to be good predictors of on-road visibility. However, retroreflectometer readings at a fixed geometry, while useful for quality assurance purposes, do not measure visibility. The actual determinant of pavement marking visibility is what the drivers see through the windshield as they drive. This paper describes current material and technology choices for making pavement markings visible at night. Data on the fundamental relationship between optics and retroreflective efficiency as it relates to road marking visibility is presented. Dry and wet conditions are considered as well as flat and structured markings. Field measurements of pavement marking luminance taken from the driver's point of view are presented to illustrate the extent to which the optical design of the pavement marking system determines nighttime visibility.

Source(s):

87th Transportation Research Board (TRB) Annual Meeting, 3M Traffic Safety Systems. For an electronic copy of this resource, please direct your request to WeatherFeedback@dot.gov.

Date: 2007

Author:

Burns, Hedblom, Miller

Keywords:


Pavement condition
Rain
Precipitation

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