A speed test for the northern pine snake (Pituophis melanoleucus) shows that it takes the snakes 2 minutes to cross a two-lane concrete road. During that time, about 70 cars may pass over a well-used highway to the New Jersey coast. On sand, a trip the same distance would last only 45 seconds, said Dane Ward, a doctoral student in environmental science at Drexel University in Philadelphia.

When a snake moves across a sandy area, it creates sandbanks that it uses to propel itself forward. Concrete does not have enough debris or grip to help with this forward motion, Ward said. "It seems that the snake is having difficulty generating enough lateral thrust to move itself farther," he told Live Science.

To compensate, snakes on concrete roads slither in an "S" motion, which isn't typical for northern pine snakes, Ward said.