Signese

I assume it's trying to be

消防通道, with the "道 in a 囗" some error?

The only thing I can figure is

a road that prevents the passage of an extinguish road

but I have no idea what that means.

I think someone originally wrote 消道, then realised it didn't mean anything so 'crossed out' the 道 and finished the sentence with 防通道.

The photo above is only the first half of the marking. It continues 禁止停车, but I couldn't fit it all in frame and still have the interesting parts legible.

There are a bunch of these all over the roadways in my community. They're stenciled, which might offer a hint as to what happened in this particular location....

jbradfor is right no doubt. It's "Firefighting through-road, no parking".

re: 'squaring' the incorrect character - I have a few young (elementary school age) students, and I've noticed that they are all taught to draw a slash through a word or letter when they make a mistake (rather than scribbling it out). This is when writing English, of course.

What do students usually do when they write a Chinese character incorrectly? Are they taught to draw a square around it?

Also, I'm wondering why the 走字底 in the last 道 is written in a different style than it is in 通...(?!?)

Interesting photo, thanks for posting!

EDIT: I just remembered that the students don't cross out their mistakes, they write parentheses around them.