On Nov. 8, 2005, Candace Dickinson was pulled over for driving in the carpool lane on Interstate 10 in Phoenix. When police sergeant Dave Norton asked how many people were in the car, “she said two as she pointed to her obvious pregnancy.”

Dickinson argued in court that since Arizona traffic laws don’t define when personhood begins, she and her unborn child constituted a carpool. Judge Dennis Freeman favored a “common-sense” interpretation of the statutes in which a person occupies a “separate and distinct … space in a vehicle.” He upheld Dickinson’s $367 fine.

California courts have encountered the same argument — it appears on the frequently asked questions page of the California Highway Patrol. The answer: “California law requires that in order to utilize the HOV lane, there must be two (or, if posted, three) separate individuals occupying seats in a vehicle. Until your ‘passenger’ is capable of riding in his or her own seat, you cannot count them.”