Ed Baiden, who heads PPG’s traffic solution business, calls it “the beauty of our system in the U.S.” that each state has its own shade of yellow paint for road markings. “There’s a Kentucky yellow, a Pennsylvania yellow, an Iowa yellow,” Mr. Baiden said. And while the federal highway administration has spent years mulling a change in the width of those yellow stripes from a minimum of 4 inches to 6 inches, 24 states have already adopted the wider standard. And the rest are headed in that direction. And that means PPG gets to sell a lot more insert-state-here yellow...