Just a nifty thought. But what if folks could ride in a carriage. It could give one, easier access to travel for some. Two, unique roleplay experiences as travel happens inside a carriage. Three, probable business ventures and jobs for adventurers given to being guides. Lastly could give groups a base of operation when traveling to dangerous reaches if say the wagon or carriage was treated as it's own room.
I think it could also diversify combat situations and give rise to Cavaliers as well as bandit groups.
Could consider adding bashable doors of different material and locks.