When I was a child, my family went on many car trips up and down the California coast. Sometimes, my father would have to pull over at a rest area if he was getting too tired to drive, and the family would take a nap in the car. I remember the sound of the freeway with the cars rumbling by loudly, and then the engine sounds trailing off into the silence of the night. But even during the wee small hours of the morning, there is always the sound of cars on the freeway.