Sorry for the confusing title, this is kind of hard to describe. I just moved to western MA. In my new town, there is this road where on one side, the speed limit goes from 40 to 30, but on the other side, rather than having the sign saying the speed limit goes up to 40 directly across the road, it is located another 1/3 to 1/2 of a mile further, meaning that oncoming cars will be legally travelling at 40 MPH in the opposite direction, but just going by signs it appears to the cars travelling in my direction that the speed limit is still 30 (I have drawn a sketch of what I am talking about below since it's difficult to describe). I always wait until I pass my 40 MPH sign before I speed up, but everyone behind me gets annoyed and starts tailgating me if I don't speed up. Also, when I'm driving behind someone, they always speed up to 40 after passing the 30 MPH sign on the opposite side of the road, even if they were driving 30 before. My question is whether it is legal to speed up to 40 once I get past the point where oncoming traffic needs to slow to 30, since from my understanding speed limits always work in "zones" where the limit is the same on both sides of the road. Or do I technically need to wait until I pass the 40 MPH sign even though it's quite far away?

Sorry for my bad drawing skills enter image description here

  • 2
    Is the 30 MPH sign facing you or the opposing lane?
    – Andy
    Commented Mar 17, 2020 at 23:42

3 Answers 3


The national standard, found in the Manual on Uniform Traffic Control Devices (MUTCD), indicates, in Section 2B.13 Speed Limit Sign:

03 Speed Limit signs, indicating speed limits for which posting is required by law, shall be located at the points of change from one speed limit to another.

It would not be legal to accelerate to the new speed before reaching the sign.

All states were required to adopt the MUTCD no later than 2012. This standard is followed by all states.

  • 3
    Not just “accelerate to the new limit”, but also “accelerate beyond the old limit”. In this situation, accelerating to 31 is only legal at the 40 sign. On the other hand, you must have slowed down to 30 when you reach a 30 sign.
    – gnasher729
    Commented May 23, 2021 at 13:46

This question is really 2 different questions in one. It can be broken down as following:

  • what is the legal speed limit in the area in question?
  • what is the best explanation for why many drivers are tailgating me when I follow the posted speed limit?

In case you just moved to MA from a different state, I'll answer the 2nd question (because it was clearly implied in the OP).

In some places it is an accepted convention to disobey speed limit signs. The convention is adhered to by most drivers and cars are only stopped by police if they travel at speeds far exceeding the convention. For example, in the NY-NJ tunnels the posted speed limit is (I believe) 25 mph. The convention is to travel at 40-50 mph. Similarly, it is a convention to travel 10 mph above all posted speed limit signs in NY/NJ. The drivers may be tailgating because you don't follow the accepted convention rather than the law.


It depends.

Massachusetts law says that a special speed regulation isn't valid unless certain hoops are jumped through by the government. They can't just put a sign wherever they like and legally enforce it.

It seems likely that the speed limits are not actually different for traffic going in opposite directions. One of the signs is likely misplaced, or perhaps a sign got knocked down and was never replaced. It's impossible for us to tell which sign it is; maybe it's supposed to be a 40 zone on both sides in that area, but it could just as well be that it's supposed to be 30 on both sides (although the lack of a sign would preclude prosecution for traffic in the other direction if it's supposed to be 30.) But you may be able to track down your local regulation establishing a speed limit on that particular road, and see where the speed zone is actually supposed to start.

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