I see many two-way trips, especially in the north. Some are "December 2025" with one reading followed by "January 2026" with a consistently different reading between trip sets. It looks like someone driving to/from grandma's house for Christmas.

The distinctly different readings on each leg of the trip suggests a rather unscientific methodology, radiation stable to the detector rather than a measurement of background. Maybe someone picked up some banana bread at grandma's for the drive home?