The 1950s postwar boom led to rapid increase of cars (and collisions) on California roads and, in turn, the development of Botts’ dots, a design solution that is just now starting to be phased back out.
Developed by Caltrans, the dots (sometimes referred to as “turtles” in the Pacific Northwest or “buttons” in Texas) were named after Dr. Elbert Dysart Botts of the California Department of Transportation (Caltrans). They were designed to address lane visibility, especially in the rain, but also serve to spook drifting drivers back to alertness (like rumble strips, embedded in pavement alongside roads).
When the first raised dots hit the streets, there were some serious issues — made of glass and nailed into the ground, they would break loose at times leaving nails exposed to puncture tires. A special epoxy created by Botts’ team helped solve the problem, allowing the dots to be affixed more easily and safely along highways and freeways.
In 1966, the California State Legislature mandated the use of the dots in all non-snowfall areas. Today, over 25,000,000 exist across the state, interspersed with raised reflective pavement markers. Some are placed over painted lines while others replace paint entirely. For a long time, these were placed by hand right next to active traffic, though safer automated solutions have also been developed (see video below).
Meanwhile, Botts’ dots have also migrated to other, mainly low-snowfall states (not only do they disappear under snow but they are also easily dislodged by plows). In snow-prone states, raised reflective markers are sometimes placed in recessed slots to avoid destruction. Other countries have adopted the dots over the years, too.
Now, however, Botts’ dots are on the chopping block, at least in California. Critics say the ceramic buttons aren’t very reflective, don’t last very long and may pose problems for autonomous vehicles.
The dots may persist in some cities, but are being phased out on state roads where heavy use forces frequent replacement (initially every ten years, but these days as often as every six months).
Better raised reflective technology will continue to replace the dots and a rumble effect will still exist, though it won’t be quite as frequent or pronounced — a driver passing over a new generation lane divider will continue to hear two bumps per second when traveling at 60 MPH.