Police often set up on Billerica Rd (Rt.129) in the parking lots of the various companies located in the industrial section of the road. Usually they are in the 270-300 Billerica Rd area but not always. Enforcement is during PM rush hour as well as later at night when the road is less traveled. Speed limit is 35 but because the road is wide and straight, 50+ is not uncommon. Police use radar and lidar and will frequently use more than one officer. The also look for aggressive driving.