From VDOT News:
FREDERICKSBURG—The Virginia Department of Transportation (VDOT) will activate its annual holiday traffic signal timing pattern to help motorists travel around 16 major shopping centers in Northern Virginia from Thanksgiving to New Year’s Day.
Holiday signal timing in Northern Virginia has been in place for more than a decade to accommodate a seasonal influx of vehicles near shopping areas. The temporary pattern is created using time- and intersection-specific traffic data from previous years.
VDOT adjusts the signal timing at more than 200 intersections in Northern Virginia. Engineers will also use traffic cameras to monitor conditions around especially congested areas such as Tysons Corner and make adjustments to help keep traffic moving.