COMPARATIVE STUDY OF ADVANCE WARNING SIGNS AT HIGH SPEED SIGNALIZED INTERSECTIONS

The effects of two dynamic signs that begin to flash a few seconds before the onset of the yellow interval and a static sign that flashes all the time were examined at rural, high-speed signalized intersections. The dynamic signs included (a) a PTSWF (prepare to stop when flashing) sign, and (b) an FSSA (flashing symbolic signal ahead) sign with green, yellow, and red circles. The static sign was a CFSSA (continuously flashing symbolic signal ahead) sign with the three circles. The effects of these signs on vehicular speeds at different segments of the intersection approach including the dilemma zone were analyzed as were the vehicle conflict rates and the responses from the drivers' surveys. The study revealed that the PTSWF and FSSA signs generally have similar effects on driver behavior. It is advantageous to consider the CFSSA sign before using the PTSWF sign because the PTSWF and FSSA signs have a few undesirable effects on vehicular speeds, unlike the CFSSA sign. The use of a PTSWF sign at a tangent approach to a high-speed signalized intersection is discouraged.