There are also distance driving competitions in Vermont. They were among the first to organize the activity. I only saw one driving photo (last one) at the Nevada site, the rest were ridden pictures. I think the chariot style cart might be a one-of, not what everyone uses. Driver looks like they are having fun, but I sure would not wish to spend my entire drive standing up in an unsprung vehicle, over rough ground. Doing a marathon can be extremely tiring for the standing Navigators, and they are only out a couple hours, with springs under carriage body, going over various kinds of ground.
You also need to consider the tires/wheels on the vehicle. Car type tires shown in the distance photo can roll nicely on rough tracks, sandy ground, be more puncture proof, but they weigh more, have greater resistance with wider widths to pull than other types of wheels. The motorcycle tires are very popular, don’t dig into sandy ground, manage gravel washout trails nicely. Tougher than bicycle wheels and light weight spokes. Have not heard of any properly inflated motorcycle wheels having issues with sideways torque in turns. The big metal spoked ones, air filled tires, horse sizes, seem quite tough. Solid tread wheels on wood or metal spokes are also pretty light weight, though tough wheels. Just know narrow widths can cut into sand, wet grass, creating more resistance for the animal pulling the vehicle.