What is the ruling on running over a child with a car, leading to his death, if the accident was unintentional and faultless, and occurred because the child ran in front of the car on a highway from which he was not permitted to cross?

If a child enters a highway that he is not permitted to enter, and the driver is unable to see him or avoid the accident, and the driver was not exceeding the speed limit, then there is no liability (daman) or expiation (kaffarah) upon him. However, if the driver could have avoided the accident but was negligent, or was not paying attention, or was exceeding the speed limit, then this is considered accidental killing (qatl khata'), and the blood money (diyah) and expiation (kaffarah) are incumbent upon him.