Is fasting and a blood-money payment incumbent upon one who caused an accident that led to the death of a woman who was standing in the middle of a highway designated for cars, and who was the cause of the accident?

If there was no negligence or causation on your part in the accident, and you were unable to avoid it, then there is no sin upon you, nor blood money (diyya), nor expiation (kaffara). For that which cannot be avoided entails no liability.