Sometimes, in the rain, the lines on the roads seem to disappear, or almost disappear. Time for a physics lesson from the Missouri Department of Transportation’s Jim Brocksmith…MoDOT uses one-and-a-half million gallons of paint to mark our roads every year, and while the paint is sticky, it adds about 13-Million pounds of glass beads to it. It’s the reflectivity of the glass beads when headlights shine on them that allows us to see the lines at night. But, when it rains, the water forms a sheen over the glass beads, dimming their reflectivity; and that’s what causes the lines to seem to disappear.Another factor is that water amplifies competing light sources, which makes it harder to see the lines. MoDOT generally schedules repainting jobs annually, although some less-traveled roads can go a couple of years between new coats of paint and some roads in metropolitan areas need new paint every six months or so. Missouri doesn’t use raised reflectors very much. We’re a snow state and snow-removing trucks have a tendency to tear reflectors right out of the roads.