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A Countdown to Cross By

counting_pedsignal (rs)So by now you are probably pretty familiar with some of the Intelligent Transportation System (ITS) technologies we use throughout the city to help with traffic. You’ve seen the dynamic message signs we use to alert travelers of roadway conditions, the traffic cameras we use to look out for incidents, and the license plate readers that help record the average travel time from an origin to a destination in the area. This data is used for SDOT’s Travelers Information website which provides a visual of real time traffic conditions.   

While these particular technologies help inform travelers in automobiles, we use ITS to help inform pedestrians as well. You know those “new” pedestrian countdown signals at intersections throughout the city? Those are designed to help pedestrians make safer decisions by informing them of the time remaining to cross the street. The countdown is used together with the traditional “walk” and “don’t walk” symbols. Timing for the pedestrian signal is calculated by measuring the curb-to-curb distance and dividing that length by 4 feet per second. This calculation is a federal standard, but can be adjusted to allow 3 ½ feet per second, or lower, if the crossing is frequently used by seniors or children. The countdown does not include the time the traffic signal is yellow or red. Once the flashing red hand turns solid and the countdown ends a crossing should be complete.

We installed countdown signals at 40 locations in 2009 and plan to install an additional 40 locations next year.