Your time spent working with the carriages and wagons of the world and their caravans have allowed you great proficiency with them. 

You gain proficiency with Vehicles(Land), if you are already proficient with them you instead gain Expertise.

You may gather the Vehicles of nearby party members and allied NPCs to form a "Wagon Train" an expert caravan which will quarter travel-time, half your needed rations, and allow your party to use hand signals to convey commands and simple orders up and down the wagon on a bonus action. 

You now use your skill with wagons to give yourself the benefit of half-cover when inside the back of a wagon, or three-quarters cover when it's covered with a canopy.