Is the driver obligated to fast for two consecutive months as atonement for accidental killing, or is paying the fidyah sufficient?

If the driver did not exceed the usual speed and did not neglect to take safety precautions, then no diyah (blood money) or kaffarah (expiation) is incumbent upon him. However, if he was negligent or exceeded the limit, then diyah and kaffarah are incumbent upon him.

The kaffarah is the freeing of a believing slave. If one cannot find one, then it is fasting for two consecutive months. The evidence for this is Allah's saying: "It is not for a believer to kill a believer except by mistake. And whoever kills a believer by mistake - then the freeing of a believing slave and a compensation payment presented to his family, unless they remit it as charity."

If the kaffarah is fasting, then one fasts for two lunar months, starting from the beginning of the month until their completion, or fasts for sixty days if one did not start from the beginning of the month.