SPEED ACTUATED ROLLOVER ADVISORY SIGNS FOR TRUCKS ON HIGHWAY EXIT RAMPS

Abstract

Special truck rollover-warning signs were examined for effectiveness in slowing tractor-trailer trucks to a speed below that associated with rollover on highway exit ramps. Advisory speeds were verified for trucks at three highway exit ramps with high truck rollover crash frequencies; rollover-warning signs specific to trucks were posted to supplement the standard speed advisory signs already in place. The supplemental rollover-warning sign was equipped with a yellow light that was triggered to flash for every second tractor-trailer truck traveling above a predetermined ramp approach speed. Mean speeds at midramp associated with the flashing sign were lower than for the nonflashing sign. Although the flashing signs did not significantly increase the number of trucks in strict compliance with maximum safe speeds, they did significantly reduce the number of trucks that were traveling more than 5 mph and 10 mph faster than the calculated maximum safe speed. These findings suggest that speed-actuated rollover advisory signs specific to trucks may reduce truck rollover crashes at highway ramps.