Opinions of the driving public have been used by transportation agencies to evaluate or score the agency’s performance and, in some cases, are used to assist in policy decisions. Subjective evaluations can serve as an indicator of customer desire, but the results are not always tied to improvements in safety or what the drivers actually need to drive safely.

A public opinion survey published by the South Dakota Department of Transportation in 1997 shows that "keeping stripes visible" was the third-highest ranked attribute out of 21 for resource allocation (money and services) as rated by both 768 members of the driving public and 32 state legislators (19). A follow-up public opinion survey in 1999 showed that 81 percent of the 734 respondents felt that poor pavement markings would "somewhat interfere" or "very likely interfere" with safe travel (20).

The American Association of Retired Persons (AARP) had 18 of their instructors drive a test course in both daylight and darkness. The drivers were interviewed, and 94 percent of the respondents said that 8-inch edge lines affect the way they drive, especially as an aid to staying on the road and in their lane (21). Research by Ohme 22) reported that drivers participating in a field detection distance evaluation generally judged wider markings as more favorable than 4-inch markings. Similar results were observed by Pietrucha et al. (23) in simulator evaluations of 8-inch versus 4-inch edge lines. However, the researchers in both cases found that perceived quality and brightness of markings did not correlate well with objective end-detection performance for markings of different widths. There have been a number of publications that document what can be considered minimum retroreflectivity levels as judged by nighttime drivers operating vehicles in a range of conditions. These studies are subjective in nature, but their results provide a reasonable sense of what drivers think they need to drive safely at night. Note, however, that the participants in these research efforts, or any typical nighttime driver, might not know what they really need from a pavement marking to drive safely. Despite this caveat, the recommendations for minimum retroreflectivity levels, based on driver preference (shown in TABLE 2) are generally consistent with results ranging from 80 to 130 mcd/m²/lx. (24, 25, 26, 27, 28).

While several studies have evaluated the public perception of pavement marking brightness, there have been no documented efforts describing how well department of transportation (DOT) visual assessments correlate to measured retroreflectivity or how well DOT personnel are able to subjectively estimate retroreflectivity. A nearly completed Texas Department of Transportation (TxDOT)-sponsored study is currently evaluating the accuracy of DOT personnel’s visual assessment of pavement marking retroreflectivity under a variety of typical nighttime roadway conditions (29).

A driving course was selected that had markings of varying retroreflectivity levels (80 to 700 mcd/m²/lx) and the following roadway characteristics:

• pavement type (new asphalt, aged asphalt, concrete, or seal coat);
• lighting conditions (no fixed lighting or fixed lighting); and
• speed (≤40 mph, 45 to 55 mph, or ≥60 mph).

State DOT personnel drove the course and were asked to visually assess the retroreflectivity. Days before the visual assessment, the researchers thoroughly measured marking retroreflectivity. The researchers are comparing the visual assessment against the measured retroreflectivity levels to determine if visual nighttime inspection is a viable method to evaluate pavement marking retroreflectivity. The researchers are also assessing if the varying conditions have any influence on the ability to consistently rate different sections.