There are a variety of places cops (almost always local) sit along the stretch of 140 between Rt. 2 exit 24 and the turn for Betty Spring Rd. in Gardner. They will usually be on one of the roads perpendicular to 140, operating radar out their side window. I’ve also seen them under the Rt. 2 overpass. I haven’t seen any unmarked cars, but marked without a light-rack is pretty common. The limit is 40mph closer to Rt. 2 and 50 further away. They usually won’t pull you over for going only a bit over the limit, depending on the traffic.