Due to cost, roads earn their stripes differently

Q: Has road striping paint changed? When I’m driving at night and in the rain it’s tough to see the lines. It doesn’t seem as reflective as it used to be.

A: You’re probably not looking for a history lesson on road paint, but it’s a cute story so I’m going to tell it. In 1911 Edward Hines was following a milk truck down the road as the truck leaked milk. The stripe of white milk inspired Hines, a member of a road commission in Michigan, to paint centerlines to separate two-way traffic.

Road paint was initially just paint. The eventual addition of tiny glass beads made the lines retroreflective, increasing nighttime visibility. Retroreflective objects reflect light back in the same direction it came from.

For a long time road paint was solvent-based, but the solvent was bad for the environment and the people who applied it. A road crew leader described it as, “nasty to work with.” Today road striping is most commonly water-based paint or thermoplastic.

Thermoplastic is expensive, but it lasts three to five years, and possibly longer. Paint is cheaper, but it may only last a year or two. And the retroreflective beads can wear away faster than the paint itself, sometimes lasting only months.

So cities are more likely to use thermoplastic markings, while counties tend to use paint. It comes down to the budget. Counties usually have more lane miles to paint, so the cost of thermoplastic markings is out of reach.

One of the biggest challenges for striping paint manufacturers is ensuring visibility in wet and dark conditions. That describes driving in Washington half of the year. Public Works departments prioritize the frequency of road striping based on traffic volume, with top-priority roads getting painted every year. But if the glass beads on a busy road wear out in less than a year, there’s not much they can do about it. To properly apply road paint you need dry weather and temperatures above 50 degrees. Those wet and dark days when you most need bright stripes are also the days when it’s not possible to apply them.

If you could invent a product that’s cheaper than paint, more durable than thermoplastic, and brighter than both, you’d make driving safer for all of us and ensure your financial future. Meanwhile, we need to admit that driving conditions are often less than ideal. We tend to think of the speed limit as the black number on the white sign. That’s the absolute maximum, but the real speed limit is the speed that is “reasonable and prudent under the conditions and having regard to the actual and potential hazards then existing.”

Doug Dahl writes a weekly column for this newspaper. He is with the state Traffic Safety Commission.