Countdown pedestrian displays are LED pedestrian displays that include a two digit numeric display, along with an overlaid hand/man display. The numeric display counts down either from the beginning of pedestrian walk interval (man) through the pedestrian clearance (hand) interval or just during the pedestrian clearance interval (hand). The countdown display period is based on the last interval display periods. They are intended to eliminate the nagging complaint about the pedestrian signal not providing enough time to cross the street. They provide feedback to the pedestrian that there is a known amount of time remaining to cross the street. I disagree with the use of countdown pedestrian displays. They actually reduce safety in my opinion. Here is why I think so.
- The time period is based on the last display period. So you must now be very careful that the pedestrian intervals remain the same or there may be a hazard when going to a shorter interval. This might happen if your controller has Max II capabilities that include the pedestrian intervals. It also might happen due to train or other preemption. The pedestrian will think they still have plenty of time and then the display will disappear. Not good.
- The overlaid display for the hand/man display presents a potential failure problem if there is a short in the display LEDs. I’ve seen it happen. This will most likely not be reflected back to the field wires and thereby will not be detected by the conflict monitor.
- I’ve also seen the display decide to countdown when the pedestrian display is steady orange and there is an opposing green vehicle display. Again not good. There is no way to failsafe the device to assure that if the countdown display is counting down, when there is an conflicting signal, that the conflict monitor would place the system in flash. I’ve seen this happen on three occasions.
- The display likely has a single control board. This means it can not be made failsafe because failures can occur that are not reflected to the field wiring so the conflict monitor will not see the failure.
- Contrary to the desire to make the crossing safer, I believe that showing the period remaining encourages pedestrians (especially children) to start across when they would not have if only the flashing hand were displayed. I believe that the best safety is provided by using appropriate pedestrian intervals and installing appropriate pedestrian information signs that explain how the signal functions and that you shouldn’t start across except when the “walking man” is displayed.
I believe that the pedestrian display should be capable of being monitored. That the design should provide totally separate display, control and power supplies for both the pedestrian walk and pedestrian clearance displays and that the countdown display should not be used. In addition, regular checks of the operation and pedestrian intervals should be made.
These are just my thought, what do you think?