Stephenson's most visible decision was to use a single pair of driving wheels, with a small carrying axle behind. This was the first 0-2-2 and first single driver locomotive. The use of single drivers gave several advantages. The weight of coupling rods was avoided and the second axle could be smaller and lightweight, as it only carried a small proportion of the weight. Rocket placed just over  tons of its  ton total weight onto its driving wheels, a higher axle load than "Sans Pareil", even though the 0-4-0 was heavier overall at 5 ton, and officially disqualified by being over the  ton limit. Early locomotive designers had been concerned that the adhesion of a locomotive's driving wheels would be inadequate, but Stephenson's past experience convinced him that this would not be a problem, particularly with the light trains of the trials contest.