What is the ruling of Islamic law on killing a man with a speeding car, and does it differ from accidental killing with a slow-moving car, and is it permissible for the family of the deceased to kill the killer or appoint someone to kill him if the ruler does not rule according to Islamic Sharia?

The prevalent type of killing in traffic accidents is accidental killing. The ruling on compensation in such cases varies according to circumstances; it is not merely speed or slowness that necessitates or negates compensation. Rather, the determining factor is negligence in safety precautions or traffic regulations. As for retribution (Qisas) and Hudud punishments, these are prerogatives of the ruler and not permissible for common people to undertake, to prevent chaos. In the case of accidental killing, the perpetrator is not killed; instead, blood money (Diyah) is obligatory upon his 'aqila (male relatives on the father's side).