Evaluating the Clarity of Highway Entrance-Ramp Directional Signs

Near the approaches of interstate and other major highways, posted directional signs warn drivers about the proper lanes for entering these high-speed limited-access roadways. These signs are intended to guide drivers with clear, concise directions, but they may instead expose drivers to ambiguous information. This ambiguity has the potential for causing accidents when the wrong lane is chosen and the driver must cross several lanes of traffic in these frequently busy interchanges. The present study examined the effectiveness of currently used interstate entrance-ramp directional signs, as well as a set of systematically manipulated alternative signs. Participants examined 94 sets of signs having various forms of simple vs. complex arrows and text (both alone and together) and for each, they were to indicate the appropriate lanes and direction to enter the interstate highway. Participants also rated the same signs according to clarity. Results indicated that text alone and text plus arrow signs consistently produced better performance and higher clarity ratings compared to signs containing arrows alone. No differences were found in the set of text statements investigated. However, differences were found for the arrow alternatives. Simple arrows (both alone and with text) produced better performance and higher clarity ratings compared to complex arrows. The data show that the current highway signs are ambiguous, and that there are alternative designs that are clearer. In real-world applications, improved signs may reduce accident rates by decreasing decision errors.