What is the state of the art in pedestrian countdown signals?
Countdown signals tell pedestrians the amount of time remaining before the flashing upraised hand changes to a solid upraised hand or "don't walk" indication. Research shows that both drivers and pedestrians tend to comply with these signals more often than with non-countdown signals.
The number of seconds displayed in the countdown is determined by the pedestrian change interval (the time before the "walk" indication changes to "don't walk"). Signal heads may be installed in place of existing non-countdown signal heads, because they use internal logic that enables them to calculate the amount of time based upon the signal inputs received over the course of several signal cycles.
Countdown signals are approved devices included in the Manual of Uniform Traffic Control Devices (MUTCD; 2003 edition Chapter 4E.07). A proposed amendment to the current MUTCD would mandate countdown signals for all crosswalks with a change interval of three seconds or less: http://mutcd.fhwa.dot.gov/resources/proposed_amend/npa_textshowingrev.pdf.
In some locations, the countdown sequence operates through the entire pedestrian phase (walk and the change interval). Many pedestrians like knowing the actual amount of time in the full pedestrian phase, so that they can elect whether to begin crossing or adjust their speed to cross more safely. For example, an older person can cross a wide intersection with greater confidence if he or she knows from the outset how much time remains for the crossing.
Research suggests that timing for pedestrian signals should take into consideration the average walking speed of different populations. A recent study found that walking speeds for older pedestrians were generally slower than for younger pedestrians by about 0.80 feet per second; pedestrians with mobility impairments and without wheelchairs had appreciably slower walking speeds.
More information:
US Department of Transportation Federal Highway Administration. (2003). Manual on Uniform Traffic Control Devices. http://mutcd.fhwa.dot.gov/HTM/2003/part4/part4e.htm
AAA Foundation for Traffic Safety. (2007). Pedestrian Signal Safety for Older Persons. http://www.aaafoundation.org/pdf/PEDsigtiming.pdf
