sprayable glow in the dark material... why aren't roads coated with this, or the center lines, or the guard rails, or the side lines?

found on http://geekologie.com/2013/10/moonstones-sprayable-blue-glow-in-the-da.php

The coating is applied in three layers, with a middle aggregate stage that absorbs UV energy during the day, which is then released as a blue glow when it's dark.

 It's kind of like a high-tech version of those glow in the dark stickers you put on the walls of your room when you were a kid. Manufacturer Pro-Teq Surfacing sees Starpath as a way for municipalities to save money, by replacing costly electric pathway lighting with the low-maintenance coating. Installing the surface takes only a few hours, leaving a durable coating that's slip and rain resistant. http://www.pro-teqsurfacing.com/pressrelease.html