What’s with the shiny buttons on old highway signs?

Imagine it’s the 1990s. “Read my lips…” A new 1993 Ford Taurus wagon bounces along an off-ramp to your right. Overhead in the night sky, an illuminated roadway guidance sign.

Road signs used to have a funny look to them at night. These green-painted signs would look black, despite being lit from underneath. In the day, text would be shaped by solid white lines. At night, text would appear as a bunch of shiny dots.

These old signs are mostly gone. Replaced with a new type of sign making called retroreflectivity. But the change is not 100% improvement. Retroreflective signs wear out. The old way built signs that would last forever.