You may have bigged me up in your own imagination..........
Warning cones and signs are there to warn people of your presence. If there are no people to warn, what kind of a fool would waste time putting out warning signs.
If there was any possibility that a member of the public would walk into our working envelope we WOULD use signs - we don't want to risk ourselves being sued do we?
Get yourself on a training course and you will see for yourselves what you are supposed to do.