Abstract: The invention provides a continuous track drive system (10) for cooperating with a pair of opposite drive wheels (18.1, 18.2) of a vehicle for converting the vehicle (12) into a half-track vehicle. In an operative configuration of the system, on each side of the vehicle, a continuous track (38) of the system runs around a drive wheel of the vehicle and a primary idler (36) of the system behind the drive wheel. The track defines between the wheel and the idler a bottom, traction run (40). A secondary idler (42) of the system bears against the outside of the track, at a position along a top run (46) of the track between the primary idler and the drive wheel, in a configuration in which the secondary idler induces and maintains an inward deflection or kink in the track for providing clearance between the track and the vehicle.