Field Evaluation of Elongated Pavement Marking Signs

Abstract

Research has shown that elongated pavement marking letters and arrows significantly improve recognition distance; however, the effect of elongated pavement marking signs, which are symbolized pavement markings that are elongated versions of signs, has not been evaluated. The goal was to evaluate the effectiveness of elongated pavement marking signs in conjunction with the post-mounted signs they complement. Results from a driving simulator evaluation indicate that recognition distance increases quadratically as elongation ratio (i.e., the ratio of height to width) increases. Considering the trade-off between cost and recognition distance, an elongation ratio of 5:1 was chosen for field evaluation of speed limit regulatory signs and curve warning signs. A before-and-after study was conducted at sites in Kansas, Missouri, and Wisconsin. Operating speeds of free-flow vehicles were used as the measure of effectiveness; speed data were collected upstream of, at, and downstream of the corresponding post-mounted sign. The speed limit sign was tested at four sites (at least one in each state) and was found to reduce operating speeds effectively at three of the four sites. A curve warning sign was tested at three sites (two in Kansas, one in Wisconsin), and operating speed reductions were observed at two of the sites. Field data results indicated that the evaluated regulatory and warning elongated pavement marking signs reduced vehicle speeds. This demonstrates they can be effective in reinforcing a warning or a regulatory message to drivers. Future research should evaluate durability and long-term effectiveness and should test other signs.