​Prepare to Stop When Flashing (PTSWF) Signs


The Ohio Department of Transportation is reviewing the statewide use of “Prepare to Stop When Flashing” signs historically used to alert drivers that a signal is turning red.  The signs are being replaced with new technology that can detect the speed of approaching vehicles and adjust the signal to prevent red-light running and crashes.

A statewide review of the signs found that drivers often speed up instead of slowing down, increasing the number and severity of crashes at intersections.

ODOT has seen a significant reduction in crashes at 14 intersections where the signs were removed within the past two years.  The average crash reductions included a 23% reduction in total crashes; 35% reduction in serious crashes; 42% reduction in angle crashes; and 50% reduction in red-light running crashes.

Many states are reexamining the practice of using the warning signs, which were often installed at isolated intersections where motorists are traveling at high speeds and not expecting to stop.  They are also used at locations where signals are difficult to see because of geography.

Many of the signs will be replaced with new, safer technology called dilemma zone detectors.  These detectors use radar technology to monitor the speed of approaching vehicles and extend the signal green time if a motorist cannot safely stop for the red light. For more information please download this file.

ODOT is also adding florescent yellow borders to many signals to improve visibility at night and longer distances.

However, not every warning sign will be removed.  Each location will be evaluated (how), and some signs may be retained, especially in areas where geography makes it difficult to see the signals at a distance.