Driver Interpretations of Existing and Potential Lane Control Signal Symbols for Freeway Traffic Management (1298-1)

This report documents the results of laboratory studies to assess motorist interpretations of the following symbols used or initially seen as potential freeway lane control signals: red X, yellow X, green downward arrow, yellow downward diagonal arrow, yellow downward arrow, circle-slash (i.e., the universal "do not" symbol), and a red X superimposed on a green arrow. The effects of flashing the red X, green arrow, and yellow arrows upon motorist interpretations were also evaluated.|Results indicate that the red X and green arrow are well understood and convey a clear, consistent meaning to drivers. Also, the yellow diagonal arrow conveys a clear, consistent message to exit a lane. The yellow X and downward arrow elicited a wide range of interpretations by motorists, and these interpretations change depending on what other LCS symbols are present in an overall LCS array at a location. Flashing displays were not found to significantly affect motorist interpretations.