turtle hit by a car

by barbara
(cedar park, tx, usa)

I saw a box turtle crossing a busy hwy. I circled around to see if I could help him across the road. The road is near a small town and at times there is no traffic. As I came back around I did not see him, finally found him upside down cracked shell but not smashed. He appeared dead, his head was out. But I studied him for quite awhile and he did not move, but as I left I thought could he have been playing dead. I do not know that much about turtles

or what happens when they are upside down. I am thinking he wasn't hit just propelled into the air by a passing car
whizzing by.