The reason I eat a vegan diet is because I do not wish to contribute to the death or suffering of animals. Therefore, I have no ethical objections to eating an animal who was accidentally killed by a car, provided that this will not encourage anyone to kill more animals in the future.

However, although I have no ethical objections to it, I choose not to eat road kill for a variety of other reasons. This is the same way in which I have no ethical objections to eating rat droppings, since this would not harm the rats in any way, but I still prefer not to eat rat droppings for a variety of other reasons.