The Massachusetts State Police have an almost constant presence in this area. Normally they sit in the median and take readings on the southbound side. I almost always see cruisers here but rarely any cars pulled over, so they must have a pretty high tolerance most of the time. I have seen cars go through here at 85+ without attracting police attention.

This last weekend (Memorial day, holiday weekend) they were hiding under an overpass at exactly mile 51.5. A trooper was standing on one side with a laser and a chase car was waiting on the other side. I got stopped but they were really, really nice about it. Wrote me a warning for 79 in a 65 (which was 2-3 mph over the actual speed of traffic by my estimate). They asked me a ton of questions about drugs and guns, so they were definitely on the hunt for contraband.

Best of luck! If you are nice and drive like an ordinary, functional human being (and your record indicates this) then they may let you off the hook for such a moderate speed. Other than that, avoid the left lane (i probably would have gotten the ticket had I been driving there). Watch your speed on the straightaways through here!