Not to bring a thread thats been dead for over 2 years back to life, but thanks suf! I just googled this since I went up 93N from work (salem exit 1) yesterday for the first time in a while, and all the spots you mention are exactly where I would have suspected them after driving it yesterday, just thankfully there weren't any in them, since I was doing 85 the whole way with no jammer
btw They sit in the median turn around right over the MA/NH border look northbound and southbound.