Alice and Bob are both residents of Somewhere, and they are both coworkers in a company located in Elsewhere. Every weekday morning and evening, Alice and Bob commute between these two towns, which lie on adjacent exits on a stretch of Highway 773. They make their commutes at roughly the same time each day.
One day, at the water cooler, Bob complained to Alice about the other cars on Highway 773. During his commutes, Bob would see many more cars that violated the speed limit than those that adhered to it. Alice, in response, stated that in her experience, the opposite was true; she had seen more cars following the speed limit during her commutes than she had seen violating it.
In spite of this apparent contradiction, both Alice and Bob were honest in stating their own observations. How can this be so?