We are often more certain than the evidence really allows.
More quotes1911: a line appears on a road near Detroit. The story says a leaking milk van supplied the idea.
Later: engineers favour yellow centre lines.
Glass beads make paint reflective.
The edge of a rural road at night remains difficult to see.
In the 1950s, studies report fewer accidents where edge lines are painted. During the following decades, marked edges and intersections spread. Seat belts spread too. Vehicles, emergency treatment, enforcement and roads keep changing around them.
That timeline is less satisfying than “paint saved hundreds of thousands of lives”. It refuses to hand one invention the entire decline. Good. Historical effects rarely arrive alone, wearing a badge.
Still, the physical problem is almost offensively simple. A driver in darkness lacks one fact at one moment: where the road ends. More data in a distant system would be impressive and useless. Reflective paint sends the missing fact back through the headlamps.
The original streak was accidental. Nobody called it transformation, built a launch event or added an intelligence layer. It was visible because milk had leaked onto the ground. Years of engineering turned that accident into standards, materials, placement and maintenance.
At night, the beam reaches the beads. A narrow line returns. The driver corrects by a few inches.