To inform drivers of road construction work from afar at night by fitting illuminants to a transparent main protector installed across a road.

A main protector 2 is made of a transparent synthetic resin (e.g. polyvinyl chloride) into a half-moon shape, and an insertion hole 3a is bored at the center section. The main protector 2 is formed firmly so as not to be broken when an automobile rides over it, and the half-moon shape allows the traveling automobile to pass without resistance, when the wheels ride over it. A nonslip body 4, made of flat plate-like or irregular rubber and having a cushioning effect and a resistance action is fixed preferably to the bottom section of the main protector 2. Illuminants 7 such as LEDs arranged at proper intervals are connected by a cord 8 for forming an indicator 6 to be inserted into the insertion hole 3a and is connected to a control apparatus via a socket 9. The indicator 6 is covered with an auxiliary protector 10 to prevent the breakage of the illuminants 7, even if the main protector 2 is broken.