01081139

Component

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 his 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 US Federal Highway Administration (FHWA) is working to establish requirements for minimum maintained retroreflectivity of pavement markings on US 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.

01081138

English

27p

2007-4

18th Biennial TRB Visibility Symposium

CD-ROM

Figures (14) ; Photos (1) ; References (20) ; Tables (4)

Binders; Correlation analysis; Dry weather; Forecasting; Geometry; Highway safety; Infrastructure; Night visibility; Optics; Rain; Reliability; Retroreflectivity; Road markings; Standardization; Traffic lanes; Visibility; Vision; Visualization; Wet weather

U.S. Federal Highway Administration

Retroreflectometers; Structure

United States

Data and Information Technology; Design; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure

TRIS, TRB, ATRI

Nov 22 2007 6:19PM

• A Review of Disability and Discomfort Glare Research and Future Direction
• Analysis of Modeled Versus On-the-Road Field Luminance of Retroreflective Signs
• Challenges to Implementation of Work Zone Lighting Guidelines
• Comparing Data Collection Scenarios Used for Examining Drivers' Sign Viewing Behavior: Closed Course Versus Open Road Environments
• Development of the Human Factors Guidelines (HFG) for Road Systems
• Driver Understanding of the Purpose of Red Retroreflective Raised Pavement Markings
• Driver-Focused Design of Retroreflective Sheeting for Traffic Signs
• Effect of Outdoor Lighting on Perception and Appreciation of End-Users
• Evaluation of Road-Sign Geometry Parameter Space
• Fluorescent Orange Retroreflective Raised Pavement Marker Color Recognition Study
• I-95 Corridor Mile Marker and Ramp Designation Signing
• Pavement Marking Visibility: Brighter Versus Wider
• Performance Assessment of Vehicle Headlamps
• Recommendations for Minimum Pavement Marking Retroreflectivity Values Based on Tarvip Analyses
• Revealing Power and Road Lighting Design
• The Relationship of Vertical Illuminance to Pedestrian Visibility in Crosswalk