How Road Signs Save Electricity

Sign up for CleanTechnica’s Weekly Substack for Zach and Scott’s in-depth analyses and high level summaries, sign up for our daily newsletter, and/or follow us on Google News!

On a recent road trip, high beams were essential. The Four Corners area might seem like a dry desert, but there are plenty of small mountain ranges to support deer in the area and even more species of sheep, goats, and homo sapiens that have adapted to living in the area. My bright LED high beams did the trick.

But, there is a downside to throwing that kind of candlepower down the roadway: overly bright signs.

Decades ago, signs weren’t that reflective. Reflectors, white paint, and even electric lighting could be used to keep drivers aware of little things like the speed limit, road hazards, and the need to stop. Incandescent headlights, especially older ones, just weren’t that bright, even with the high beams engaged. Even with the brightest white and yellow paint plus stuck on reflectors, rural roads could be difficult to navigate at night in rural areas.

But, an often underappreciated technology came to the rescue:

Seeing anything requires light to be reflected, but the process is kind of random. During the day, when the sun is bathing the earth with photons, even if a tiny fraction of a percent happen to bounce off something toward your eyeballs, there’s still enough light for drivers to see clearly.

At night, the supply of those wave-particles that we use to see are in much shorter supply. So, even when something like a car’s headlight sends a stream of light onto objects ahead of your car, there still might not be enough light to read road signs clearly before you’re already passing them. So, road departments and later departments of transportation have been trying all sorts of different things to make it easier.

Retroreflective technology has been in development for a century. Those of us old enough to remember older roads probably remember reflectors on road signs, weird beads in the lettering, electric lights, and some of these other approaches.

As the video explains, each little technological improvement led to more light being reflected toward the source of the light and less being reflected in other directions. As the size of the retroreflectors decreased and the amount of light going in the right direction increased, the efficiency of the technology got better and better. It even got so good that engineers had to start putting in imperfections to scatter the light a bit, because drivers tend to sit higher than their headlights.

If materials scientists and engineers hadn’t worked on this problem, motoring at night might be pretty different today. Instead of road signs that reflect so much light back at you that bright LEDs are a little too much, we would probably instead see little solar panels and batteries on rural signs to light the more important ones up. Or, we’d have to rely on some sort of in-car databases in the infotainment to keep up with important information at night.

Or, worst of all, we might even see far lower night-time speed limits. Without retroreflective paint for stripes, bright signage, and better headlights, states like Texas would probably still have lower speed limits at night!

A little energy efficiency, even for reflection, can go a long way!