The ruling on praying in a car while it is moving and may deviate from the qiblah?

Al-Huwaini: What is the validity of praying the nafilah in a car while it is moving, given that it deviates from the qiblah?

The Shaykh : There is no difference from this perspective between a car and a mount. However, there is a difference between driving a car on a crowded road and driving on an empty road. In the second case, I see no difference between praying the nafilah in a car or on a mount. As for the first case—the case of congestion—one cannot focus his mind and maintain khushu' in prayer while driving a car on roads crowded with people. Therefore, we do not advise him to perform this prayer.