Not sure something like this has a real purpose. My take on it is that people driving at night would not know what it is and then swerve to avoid it. Even if you just put reflective paint around the edge you would probably get the same reaction. Nope, if you decide to illuminate grates and manhole covers it would take a good while before everyone got used to the idea and knew they didn't have to necessarily swerve to avoid it....which they would likely do anyway.