One February afternoon about 5 years ago (I was a teacher in the DFW area), I was headed home at the end of the school day. After turning from the parking lot onto a highway that dips into a depression then rises back up again over a distance of about a quarter mile, I was the only vehicle in sight until I started the climb. As I was going up, a minivan with its headlights on appeared in the opposite lane, followed by a vehicle about two car-lengths behind, and passed me horn blaring. I wondered why, and when I ...