My car tracks my average speed for some reason, and I believe it's based on engine hours vs. distance. After 2½ years and ~70,000km it's stayed pretty consistent at about 60km/h.
My driving is probably 90% highway by distance, or 60% by time.
This is what I came here to say. Even short distances.
Basically, any time you're describing a trip to a destination, it's in time, based on the mode of travel. Hell, I even describe our family hikes in time it takes our littles to walk it, then estimate how long it would take an adult.
My kids school is 3 minutes away or an 8 minute adult-pace bike ride. Fucked if I know how many km that is.