The concept of "was the driver seat" can be expressed in a variety of ways, and its antonyms will depend on the specific context in which it is being used. Some possible opposites might include, "was not the driver seat," "was a passenger seat," or "was in the backseat." Another possible antonym might be to use a different verb altogether, such as "walked" or "rode." Ultimately, the most appropriate antonym will depend on the sentence or phrase in which the phrase "was the driver seat" is being used, and the specific meaning that the speaker or writer is trying to convey.