If we're walking together, can I give you a piggyback or something? It's death walking somewhere for a purpose and taking like 50% longer to get there because your friend/partner/whoever doesn't walk 6 km/h.

6 km/h should be default. 1 km/10 mins just makes estimating arrival times perfect (1.5 km is 15 mins). And it's not that fast even.

Edit: I've taken your inch and asked for a mile