The MUTCD (Manual for Uniform Traffic Control Devices) is a bit confused (and a lot lacking) when it comes to signs for temporary traffic control devices. Orange is supposed to be the color for temporary traffic control devices, yet the manual uses regulatory (white) signs for sidewalks in construction zones. A white sign indicates permanence, an orange sign indicates temporary. That subtlety seems beyond the comprehension of the people who write the MUTCD, but I’m here to help them. Below are the pairs of signs for sidewalk closure in construction zones. On the left is the existing MUTCD sign, on the right is the sign as it should be.
There might be situations in which the permanent, white regulatory sign might be appropriate, though the number of such situations is and should be rare. Sidewalks should be continuous, not broken, not closed.
Note that I did not include the R9-10 sign with arrows pointing both ways, since I can’t think of a context in which that would be the appropriate sign. Unless someone can, it should be removed from the MUTCD.
I have also suggested that all TTC signs be given a unique code, not M, not R, not W, but perhaps T.