There are cops sitting in marked and unmarked cars parked on 172nd Street and East Bound Grand Central Parkway Service Road with Radar/ Laser gun waiting for speeders. Sometimes they are on 170th Street. By the time you see him, its too late. After you pass 168th Street, just stay under 30mph. That little stretch will tempt you to do 60, especially when you get the light at 168ST. I normally see them in the PM Rush, they hide in a dark spot at the corner.