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All About Pedestrian and Traffic Signals
Traffic signals are installed at intersections to create gaps in the traffic flow of a street, allowing pedestrians to cross safely. The City of Alexandria manages nearly 250 signalized intersections and all but a handful have either pedestrian signals, pushbuttons, countdown timers or audible pedestrian signals.
Still, the City recognizes that it can improve pedestrian safety at many intersections with a combination of signalization, striping and pedestrian enhancements. We are in the process of adding new pedestrian countdown timers and audible signals where appropriate. The information below is intended to help shed some light on one aspect of intersection crossings: pedestrian signals.
In areas such as Old Town, on Mount Vernon Avenue in Arlandria or along some sections of Duke Street, signals may be closely spaced – sometimes every block. This is important because high pedestrian traffic exists during a majority of the day. In these situations, the City of Alexandria uses fixed-time signals to consistently allow pedestrian crossing opportunities.
Pedestrian "cycles" (the amount of time dedicated to a pedestrian crossing during different phases of a traffic signal) are generally timed based upon a maximum walking speed of 3.5 ft per second. In areas with a heavy concentration of children or older adults, a lower speed of less than 3.5 feet per second may be used to determine pedestrian clearance time.
The simplest form of pedestrian signal includes three types of indicators:
The City of Alexandria has installed countdown timers at more than 50 intersections around the city and adds approximately five new intersections a year to this total (the countdown timers cost approximately $1,000 each or approximately $5,000 per intersection). This cost is occasionally borne by developers.
Pedestrian Pushbuttton Signals 101 – Why They're Not Well Understood!
Pushbuttons allow pedestrians to call up a walk signal. However, the way pedestrian signals work is not well understood. (A 2004 article in the New York Times fanned the flames for many cynical pedestrians when it concluded that many pedestrian pushbuttons in the Big Apple do not work and essentially function as mechanical placebos! Many of the pedestrian pushbuttons in Alexandria are operationally different, though.)
By pushing a pedestrian button, you are notifying the computerized signal controller at the intersection that you are waiting to cross. Although many people assume this always shortens the green light for motorists and hastens the pedestrian cycle, in fact it does not always do this. In some cases, the pedestrian pushbutton works to ensure that a full "walk" phase will take place at the end of the usual green traffic phase, thus allowing a pedestrian sufficient time to cross the street.
At some lights, the pushbutton shortens the green light for motorists and allows pedestrians to cross sooner. The City is also experimenting with "Leading Pedestrian Intervals." A "Leading Pedestrian Interval" gives pedestrians an advance walk signal before motorists get a green light, giving the pedestrian several seconds to start in the crosswalk when there is a concurrent signal. This makes pedestrians more visible to motorists and motorists more likely to yield to them. However, this is not always a good solution for pedestrians with mobility impairments because there is not audible warning of the pedestrian phase.
Where pedestrian crossings are particularly challenging for those with mobility impairments, the City of Alexandria also seeks to install accessible pedestrian signals. Alexandria uses a pushbutton-integrated system that has a speaker and vibrating surface or arrow at the pedestrian button. The sound comes from the pedestrian pushbutton housing, rather than the pedestrian head. This type has been common in Europe and Australia for years.
A constant quiet locator tone, repeating once per second, provides information to the blind individual about the presence of a pedestrian pushbutton and its location. The locator tone is only intended to be audible 2 to 4 meters (6 to 12 feet) from the pole or from the building line, whichever is less.
The walk interval is indicated by the same tone at a faster repetition rate and by a speech message.
Some of the pushbuttons on Alexandria intersections are larger because they are newer and more easily used by those with mobility impairments. The City is in the process of replacing pushbuttons where appropriate.
It is IMPORTANT to note that the pushbuttons in place at Alexandria intersections are NOT "placebos" and are intended to function properly! If you believe a button is not working properly call (703) 746-4747 or visit the City's online complaint form.
How can I ask about a specific intersection?
To reach the city's Pedestrian and Bicycle Program, call (703) 746-4088.