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University of Iowa News Release

Release: April 16, 2003

(Photo: Tom Schnell, assistant professor of mechanical and industrial engineering and OPL director in the UI Center for Computer Aided Design)

Researchers Use $400,000 Grant To Study Yellow Highway Lines

Few drivers likely consider the importance of yellow pavement marking lines, even though yellow – unlike white -- lines indicate opposite-moving traffic and their distinctive yellow color is a part of the national traffic code.

But researchers at the University of Iowa College of Engineering Operator Performance Laboratory (OPL) are using a $400,000 grant from the National Cooperative Highway Research Program of the Transportation Research Board to learn how drivers perceive the difference between yellow and white lines.

The goal of the study is to develop recommendations for various highway and traffic-related agencies and provide a scientific foundation for national standards on pavement marking color, according to Tom Schnell, assistant professor of mechanical and industrial engineering and OPL director in the UI Center for Computer Aided Design.

“Road markings allow drivers to safely navigate the highway without the need to look away from the road, so they help reduce accidents,” he says. “However, in order to function properly, they must be of a color and configuration correctly perceived by the driver. Improperly applied or poorly maintained pavement markings can create a hazard.”

For example, when manufacturers removed lead chromates from yellow pigments used in pavement markings some years ago, many of the substitute materials appeared white at night. Incorrect identification of pavement marking color may present a significant problem because the color yellow – not white -- indicates the location of traffic moving in the opposite direction. Schnell hopes to prevent similar problems for today’s drivers by evaluating existing pavement markings, studying human color perception and noting how the choice of material specifications and other variables affect color rendition and perception. Those specifications include: pigment and binder materials, illumination and viewing angularity, vehicle headlight position, vehicle headlight type, vehicle height above the roadway, vehicle windshield tint, and other factors.

"Our intent is to define the ranges of color shades that will guarantee a specified level of correct identification under a wide range of illumination and viewing conditions for a large number of observers,” he says.

Schnell notes that one outcome of the study will be the scientific basis for national standards for maintaining the visibility and consistency of highway centerlines.

As the principle investigator, the UI is subcontracting a portion of the study to the National Institute of Standards and Technology (NIST). Schnell notes that NIST is a valuable partner because of its expertise in measuring light color and intensity. "They are the world's best agency for the measurement of light, and we are glad that we could team up with the NIST,” he says.

STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 371, Iowa City, Iowa 52242-2500.

CONTACTS: Gary Galluzzo, University of Iowa News Services 319-384-0012,