On your left, just before the Fairfax County Parkway exit, there is a HOV ramp that rises up to an overpass. Under the ramp is a spot that State Troopers sit and take readings. You can not see them until you have passed the ramp and by then it is too late. The Officers have a 5 mile view down the highway and will sometimes work in teams, with one takeing speed readings and the other doing the road work further down the highway. Be careful on this strech, For the most part you will not be harrased for doing 60, but much above that on this 55mph 5 lane highway and you will get pulled over.