Botts' dots

Botts' dots are round non-reflective raised pavement markers. Botts' dots may also be called turtles (Washington and Oregon) or buttons (Texas and other southern states). In many parts of the U.S. and other countries, Botts' dots are used, along with reflective raised pavement markers, to mark lanes on highways and arterial roads. They provide tactile feedback to drivers when moving across designated travel lanes, and are analogous to rumble strips.