We lived in a development up on a rocky ridge a while back. Every year in April I would start killing them like that and see them dead in the road. They den up like rattlers.
"In October the Copperhead retreats to its underground den to hibernate until late February or early March. Dens are most often in rocky hillsides with southern or eastern exposure to the sun. These "snake dens" will be returned to year after year and may contain a large number of snakes. In late summer through mid-October, between 1 and 14 young are born alive rather than hatched from eggs."
https://www.copperhead-snake.com/ 
