On Route 3 — cop parks in turnaround near Old Billerica Rd.
There is a turnaround on Rt. 3 that staties like to park in. You run into it going over a hill and under the Old Billerica Rd. overpass from the north, so you can’t really see it until it’s too late. Coming from the south, you’ll have lots of room to see him — just slow down to ~70 when going over the hill at the Rt. 62 on/off ramps to make sure he’s not there.
I’ve done low 70s on Rt. 3 past speed traps/cops on patrol and not gotten pulled over, but I try not to exceed 70 when running toward any possible speed trap location.