What single visual feature distinguishes construction and maintenance signs from every other category of road sign?

Why C is correct

Orange is reserved exclusively for temporary traffic control, so the colour alone tells a driver two things before a single word is read: the road ahead does not match what the driver expects of it, and whatever is written applies now rather than permanently. The colour is also unusually conspicuous against most backgrounds and in poor light, which matters when the hazard is a lane shift rather than a fixed curve. Because these signs are temporary, their message supersedes the permanent signage nearby — including the posted limit.

Why the other options are wrong

A. They always state a reduced numeric speed limit

Many work-zone signs carry no number at all: lane shift arrows, flaggers ahead, uneven pavement. Waiting for a speed figure means missing most of what these signs say.

B. They are purely advisory and may be ignored when no workers are visible

Advisory is the wrong category entirely. Workers are standing within arm's length of live traffic lanes, and the whole legal framework around these signs reflects that asymmetry. Ignoring one is not rejecting advice; it is disobeying a lawful instruction issued for somebody who was relying on every driver following it.

D. They are the only diamond-shaped signs in the system

Diamonds are shared with permanent warning signs. Shape cannot separate a curve warning from a lane closure, which is exactly why a colour was reserved for one of them.

On the road

A driver follows orange lane-shift arrows across a stretch they have driven for years, ignoring the lane they remember. The arrows are correct and the memory is wrong, because somebody rebuilt that road last Tuesday. Muscle memory is genuinely dangerous under exactly these conditions, which is another reason the colour was reserved for temporary control rather than anything static.

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