This paper presents a theoretical study on the directional stability of multi-articulated vehicles with multiple axles. The vehicle dynamics model is derived in the horizontal plane having degrees of freedom of vehicle side-slipping and yawing. For an equal vertical load of each axle as well as an equal cornering coefficient of each wheel of the multiple axles, the equations of motion can be reduced to ones with a single axle and additional terms that are functions of the number of axles and

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... distances between them. Two types of tractor and double-trailer combinations with multiple axles are examined with regard to straight running stability as well as steering sensitivity in steady-state turning. Non-oscillatory stability incorporating steering sensitivity is analyzed using the stability factor of multiple-axle vehicle combinations. A parameter study of oscillatory stability and steering sensitivity is conducted, and the following conclusions are drawn. (1) The terms on multiple axles are added in the tractor yawing moment and part of the trailer yawing moment. (2) Multiple-axle vehicles differ from single-axle vehicles in non-oscillatory stability and steering sensitivity. (3) A multiple-axle dolly improves oscillatory stability.