ACTIVE ADVANCE WARNING SIGNS AT HIGH-SPEED SIGNALIZED INTERSECTIONS: RESULTS OF A STUDY IN OHIO

The effectiveness of several active advance warning signs at high-speed signalized intersections in Ohio was evaluated. The signs included the Prepare To Stop When Flashing (PTSWF), Flashing Symbolic Signal Ahead (FSSA), Continuously Flashing Symbolic Signal Ahead (CFSSA), and Passive Symbolic Signal Ahead (PSSA) signs. The research was designed as a before and after study with control sites. The measures of effectiveness included vehicular speeds at various segments of the intersection approach, vehicle conflict rates, and ratings by drivers. The study found that the effects of the signs on drivers varied among intersections with tangent and curved approaches. The PTSWF or FSSA signs generally encouraged high speed when the flasher was inactive and the signal indication was either green or yellow. Fewer motorists related the PTSWF sign to the traffic signal. In general, active advance warning signs should be discouraged at high-speed signalized intersections, particularly at intersections with tangent approach. At high-speed signalized intersections with curved approach, the CFSSA sign seems to be preferable to the PTSWF sign for reducing speed. Further study to examine the possible use of the FSSA sign in providing a better alternative at locations where the PTSWF sign cannot be effective is recommended.