Sentence:  In contrast to the methods used in New England all the lumber from the high Sierras is taken out in the summer instead of the winter. Teams of about seven pairs of horses, or mules, or traction engines, are used. Teams draw two or three wagons, and are managed by one driver who rides on a <WSD>wheelhorse</WSD> and guides with one rein, whip and voice. 
Meaning of the word marked with <WSD> tags:  One of a team of horses which is nearest to the wheels of a carriage, as opposed to a leader or forward horse.