How do I introduce a horse to pulling a vehicle for the first time?

Introducing a vehicle to a horse that has been ground driven and accepted harness requires the same patient, progressive approach that each preceding stage has required. The sounds and sensations of a vehicle following the horse are novel and potentially alarming, and the fact that the vehicle cannot be removed quickly if the horse becomes reactive makes this introduction stage one where extra caution produces significant safety dividends. The first introduction is typically to the shafts of the vehicle without the vehicle attached — allowing the horse to feel the shafts alongside its body and to hear the sounds of the shaft tips being manipulated while standing still in harness. A horse that accepts the shafts alongside its body without concern is ready for the vehicle to be attached at a standstill, where it can be examined, approached, and backed away from without any movement. The first movement with the vehicle attached is typically at a walk, with a handler at the horse's head providing both safety backup and a focus point for the horse's attention. The sounds of the vehicle wheels on the ground, the slight resistance of the vehicle's weight against the traces, and the movement of the vehicle in the horse's peripheral vision are all novel experiences that the first movement session introduces simultaneously. Multiple sessions of walking calmly with the vehicle — in the arena, outside, on varied surfaces — build the horse's acceptance of the complete vehicle experience before any actual driven session occurs.