The TowPlow is a novel type of snowplow that consists of a conventional snowplow vehicle and a steerable, plow-mounted trailer. The system is used to plow two typical traffic lanes simultaneously. In this paper, a nonlinear dynamic model of the TowPlow is developed for longitudinal, lateral, and yaw motions. The model considers nonlinearity through a modified Dugoff’s tire friction model, tire rotation dynamics, and quasi-static load transfer. The model is verified through steady-state and transient tests on an actual TowPlow system. A new snow resistance model is developed to allow simulation of the TowPlow in snow clearing operations. Then, active steering control of the trailer axle is derived with the goal of improving safety and efficiency of the TowPlow. The comparison of the simulation results between the controlled system and the uncontrolled system for cornering, slalom, up and down hill, and split friction coefficient braking maneuvers clearly demonstrates the efficacy of active steering control for the trailer axle of the TowPlow.