當列車行駛在軌道時，車輪不單只有緃向或是垂直運動，而且還存在著潛滑運動。潛滑運動乃是由於輪/軌間的動態接觸力和車輪及鐵軌頭形狀等因素，造成列車行駛在軌道會產生左右移動現象，吾人稱之為蛇行(Hunting)。
本文探討行進中之軌道車輛在垂直及側向之動態特性，文中首先利用牛頓第二定律(Newton’s Second Law)與有限元素法(Finite Element Method)得到車輛-軌道系統各構件之離散化運動方程式，再組成車輛及軌道系統運動方程式。對於列車/軌道系統而言，輪/軌間的交互作用力是一項很重要的因素，該交互作用力聯結了車輛和軌道兩大部份，包含有正向接觸力和切線潛滑力。正向接觸力以非線性赫茲(Hertzian)彈性接觸理論來模擬，切線潛滑力則以卡克(Kalker)線性潛滑理論來模擬，並使用Heuristic修正理論使潛滑力在合理值範圍內。最後使用紐馬克（Newmark）數值分析法，求得車輛及軌道系統在每一個時刻之響應數值解。
研究結果顯示，當輪/軌摩擦係數變大時，輪/軌側向接觸力振幅亦會隨著變大，當車輛行駛於彎道時，較高的車速、較小的彎曲半徑、超高角不足及過大的情況，均會使車輛及軌道各構件產生較劇烈的位移、速度及加速度振幅變化。

When a vehicle moves along a track, each wheel has not only longitudinal and vertical motion but also sliding motion. Sliding motion is influenced by factors such as the dynamic contact between wheels and tracks and the shapes of wheels and rails. The motion which makes wheels move left and right while proceeding is called “hunting”.
The vertical and lateral dynamic characteristics of a moving vehicle is investigated in the thesis. First, apply Newton’s second law and finite element method to get the discretized equations of each component of the vehicle and track systems, respectively. These equations can be further combined to yield the equations of motion for the vehicle and track systems, respectively. For vehicle/track systems, the interaction between wheels and tracks is an important factor. This interactive forces include the normal contact force and tangential creep force. The normal contact force can be simulated by nonlinear Hertzian’s theory for elastic contacts. The tangential creep force can be simulated by Kalker’s linear theory. The tangential creep force calculated from Kalker’s linear theory is further modified by the heuristic theory to control its range. Finally, Newmark’s method is used to obtain the values of the dynamic responses of every component of the vehicle and track systems at each time step.
The research findings indicate that the larger the friction coefficient between the wheel and track is, the larger the amplitude of the lateral contact force between the wheel and track will be. When a vehicle moves along a curve track, each component of the vehicle and track systems will have more violent changes in displacement,velocity and acceleration under the following conditions: high speeds, shorter curve radii, and improper cant angles.

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