A vehicle comprising: wheels (w); and a steering module configured to steer the wheels (w) in one of two mutually opposite right and left directions, or in one and another of the two mutually opposite right and left directions, respectively, wherein a caster angle (Φ) is set within a range of ±3 degrees relative to a kingpin angle (θ), the steering module comprises: a pair of first and second rack bars (10 and 11) configured to steer the pair of right and left wheels (w) in one of the two mutually opposite right and left directions, or one and another of the two mutually opposite right and left directions, respectively; and a rack bar moving means for moving the first and second rack bars (10 and 11) in one of two opposite directions along which rack teeth of the first and second rack bars (10 and 11) are arranged, or in one and another of the two opposite directions, respectively, by a same distance, and wherein the rack bar moving means comprises: a synchronizing gear assembly (22 and 23) meshing with the first and second rack bars (10 and 11) such that a movement of the first rack bar in one of the two opposite directions is converted to a movement of the second rack bar in another of the two opposite directions; a first pinion gear meshing with the first rack bar; a second pinion gear meshing with the second rack bar; and a coupling mechanism configured such that the first pinion gear and the second pinion gear can be coupled together or uncoupled from each other by the coupling mechanism. wheels (w); and a steering module configured to steer the wheels (w) in one of two mutually opposite right and left directions, or in one and another of the two mutually opposite right and left directions, respectively, wherein a caster angle (Φ) is set within a range of ±3 degrees relative to a kingpin angle (θ), the steering module comprises: a pair of first and second rack bars (10 and 11) configured to steer the pair of right and left wheels (w) in one of the two mutually opposite right and left directions, or one and another of the two mutually opposite right and left directions, respectively; and a rack bar moving means for moving the first and second rack bars (10 and 11) in one of two opposite directions along which rack teeth of the first and second rack bars (10 and 11) are arranged, or in one and another of the two opposite directions, respectively, by a same distance, and wherein the rack bar moving means comprises: a synchronizing gear assembly (22 and 23) meshing with the first and second rack bars (10 and 11) such that a movement of the first rack bar in one of the two opposite directions is converted to a movement of the second rack bar in another of the two opposite directions; a first pinion gear meshing with the first rack bar; a second pinion gear meshing with the second rack bar; and a coupling mechanism configured such that the first pinion gear and the second pinion gear can be coupled together or uncoupled from each other by the coupling mechanism. a pair of first and second rack bars (10 and 11) configured to steer the pair of right and left wheels (w) in one of the two mutually opposite right and left directions, or one and another of the two mutually opposite right and left directions, respectively; and a rack bar moving means for moving the first and second rack bars (10 and 11) in one of two opposite directions along which rack teeth of the first and second rack bars (10 and 11) are arranged, or in one and another of the two opposite directions, respectively, by a same distance, and wherein the rack bar moving means comprises: a synchronizing gear assembly (22 and 23) meshing with the first and second rack bars (10 and 11) such that a movement of the first rack bar in one of the two opposite directions is converted to a movement of the second rack bar in another of the two opposite directions; a first pinion gear meshing with the first rack bar; a second pinion gear meshing with the second rack bar; and a coupling mechanism configured such that the first pinion gear and the second pinion gear can be coupled together or uncoupled from each other by the coupling mechanism. a synchronizing gear assembly (22 and 23) meshing with the first and second rack bars (10 and 11) such that a movement of the first rack bar in one of the two opposite directions is converted to a movement of the second rack bar in another of the two opposite directions; a first pinion gear meshing with the first rack bar; a second pinion gear meshing with the second rack bar; and a coupling mechanism configured such that the first pinion gear and the second pinion gear can be coupled together or uncoupled from each other by the coupling mechanism.