海運軸輻路網折扣係數之研究

Abstract

隨著船舶大型化及航商節省成本的考量，定期貨櫃船運逐漸發展成海運軸輻路網的經營型態。謝尚行、張斐茹（2001）以O’Kelly（1987）的軸輻路網模式為基礎，建立一海運軸輻路網模式，將貨櫃母船與子船的單位運送成本比值定義為折扣係數（discount factor），此折扣係數為模式求解的關鍵；而在相關軸輻路網模式中也都以折扣係數來表現出軸心點間的規模經濟性，但都僅將折扣係數設為定值，容易造成模式求解的錯誤。目前並未有研究針對某一運輸路網之折扣係數的值應是多少，或影響折扣係數的各種因素做一深入探討，因此本研究以定期貨櫃航運為研究對象，建構一折扣係數模式，確認出折扣係數的存在性，並估計出主線上折扣係數的值。而利用本研究模式求解出的結果：單位運送成本會依船型的增加而呈遞減的趨勢及在兩港距離增加時較適合利用大型船舶來營運；可藉以驗證Kendall（1972）與Jasson & Sheneerson（1982）提出的船舶規模經濟理論以及Talley（1990）針對最適貨櫃船型研究所提出結論。

International containerships have been running the pattern of the hub-and-spoke networks for twenty years. Based on the model of O'Kelly (1987), Hsieh and Chang（2001）proposed a marine hub-and-spoke network model which defined the discount factor（α）as the ratio of the unit travel cost of large ships to that of small ones. Most of the hub-and-spoke network models also used α to represent the economies of scale on interhub links. However, it is assumed that α is a constant value in their models so as to result in the miscalculation of the objective function. Up to now, neither do papers analyze influence of α on the model nor do papers calculate the exact value of α. In this paper, a discount factor model dedicates the fact of α and calculates the real value of α on main routes. The results of this paper are: one is that the unit travel cost is decreasing while the ship size is increasing which can prove the ship scale economies theory. ( Kendall,1972; Jasson & Sheneerson,1982.) The other is that optimal containership size increases as the distance of the route increases which can prove the theory of the optimal containership size. ( Talley,1990.)