Is the driver considered sinful for endangering the lives of passengers when attempting to avoid colliding with a corpse on the road? Is it considered a sin if he touches the corpse during the maneuver, and what is its expiation?

You are obligated to avoid running over a deceased person's body with a car as much as possible, because the sanctity of the dead is like the sanctity of the living, and breaking the bone of a dead person is like breaking it while they are alive. However, if avoiding running over the deceased would expose the lives of the living to certain danger, then preserving the lives of the living takes precedence, because it involves committing the lesser of two harms. And if the body suddenly appeared before you and you found no alternative but to hit it, then there is no sin upon you and no expiation.