Just for clarity, As long as do not drive AROUND the "Road Closed" barrier, you should be ok.
"by posting or causing to be posted signs to that effect, or placing or causing to be placed traffic control devices as prescribed in the regulations.
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It's all about the location of the signage, it works the same as Speed Limit signs, in this case the closure area is limited to an area between the signs. If an officer, or whomever is responsible for the the signs, puts up 2 signs at a 4-way intersection, then I would see that as 1 road being closed. Most of the time when I have seen road closed signs there have been officers present and it was done in a way that closes only a block of road, i.e. you can drive around it.