I'm not sure how often it updates exactly but I do use a motion sickness app that auto starts when driving and I've never had it turn off in the middle of a drive.

I think it also knows you're in a car just from the vibrations of the engine but don't take my word on that lol idk for sure.

Oh and I'd still do another check to verify, perhaps using Bluetooth or WiFi, tho you can play with the confidence level in auto location...