Police are constantly on Glade, especially on the stretch between Colts Neck and Soapstone. They are frequently around the neighborhood Deepwood, which is atop a hill on which it is easy to gain speed. Police are usually reasonable about going 5 mph over but any over and you’re likely in trouble. Those two hills are easy to gain speed on (I drive 45-50 mph on any pretty much any road in Reston) and driving towards Soapstone there is a hard curve that I have often encountered police coming around.