航空貨運站作業延滯對進口時效性商品之影響研究

Abstract

航空貨運站為航空貨運中空側與陸側交接之環節且相關作業單位甚多、作業繁瑣，若其中任一作業環節產生之時程延滯，均可能對航空貨運站其他作業造成影響，特別在海關查驗部分，近年來因911事件及各種動植物流行病之影響，造成海關對於貨物之查驗更加嚴格、耗時。其中特別以進口通關作業之時間延滯最為明顯，貨品之存倉時間普遍長達四至五天，因使用航空運輸之貨物的時間價值普遍高於使用一般運輸之貨物，因而若商品於通關過程發生時程延滯，將可能導致貨物原有功能喪失或減低其剩餘價值，增加貨主、物流業者之存貨成本。 本研究首先依據貨物於航空貨運站進口通關之物流、資訊流作業流程，構建航空貨運站進口通關作業網路，並以解析性之方法分析各航機之貨物於航空貨運站進口通關網路流動之時程，構建時程延滯模式，由主要變數間之關係探討各航機貨物間形成延滯之原因及延滯之擴散情形。繼而，探討進口通關網路遭遇偶發性臨時事件所產生之時程延滯，對各航機貨物於通關網路中流動時程之影響，並構建時程延滯擴散模式。進一步深入探討各項貨物於通關網路中之流動時程，構建貨物通關時間評估演算法，並結合時程延滯模式與貨物通關時間評估演算法以分析造成貨物通關時程延滯之因素；繼而藉由分析各項進口通關作業之特性，擬定相關延滯控制策略，藉由改善航空貨運站之進口作業方式，以提升航空貨運站之進口通關作業效率，並減少貨主、物流業者之存貨成本。最後，以中正機場航空貨運站民營化成立之華儲股份有限公司為例，蒐集進口通關作業相關資料進行範例分析，以驗證本研究所構建模式在實際應用上之可行性與模式之發展潛力。 範例分析結果顯示，繳納關稅作業為通關作業流程中貨物平均等待時間最長之作業，此外尖峰時段中愈晚抵達航班之貨物因遭受先行抵達航班貨物之推擠因此通關之平均等待時間愈長。愈接近空側之作業貨物遭受前一航班貨物推擠之情況愈為明顯，愈接近通關網路下游則同航機間貨物之推擠愈為明顯。而透過改變同航機貨物之通關順序，可有效降低同航班貨物於通關過程產生之總存貨成本，且尖峰時段中愈晚抵達航班之總存貨成本降幅愈大。尖峰時段中，若僅增加單一作業之作業容量，可降低貨物於該作業之等待時間，但卻造成貨物於接續作業之等待時間上升，且上升幅度近似於降低之幅度，若同時提升各項作業之作業容量，則原作業容量愈少之作業所降低的等待時間愈長。實務上，研究結果可提供航空貨運站作為改善進口通關流程時之參考。

The processing of cargos in air terminals is usually operated by many operators such as airlines, forwarders, custom, security related agencies, etc. The custom clearance process of import cargos in air terminals is very complicated and time consuming. Once there occur any incidents or additional requirements on any of custom clearance procedures frequently incur delay and delay propagation on interrelated process in the terminals. The security check due to 911 events and quarantine measures due to bird flu epidemic are the recent examples. The study first develops a network representation on import cargo and information flows processed in all procedures of the air terminal. Then the study explores the causes and characteristics of delays on cargo processing and develops the delay propagation model using analytical methods. The study explores the delay caused by processing order and contingencies, and evaluates the influence on cargo processing to develop the delay model. The study further analyzes characteristics of delays on cargo processing in the network including all import procedures and develops an algorithm using corrected labeling method find the leant time path. Combining delay propagation model and the algorithm, the study further explores the factors of delay propagation and consequently illuminates the characteristics of varied cargo processing procedures. Based on above analyses, the study further proposes some strategies that aim at improving cargo terminal processing and enhance the efficiency of the procedure thereby reducing the inventory cost of shippers. Finally, Taiwan Air Cargo Terminal (TACT) at the CKS airport terminal is used as an example to demonstrate the application and feasibility of the developed models. Results of this study reveal that tariffing procedure is the most time-consuming task among all tasks of import cargo processing. In addition, in rush hours the later the cargos of a flight arrives the longer it takes to undergo cargo processing due to delay caused by earlier flight cargos. Moreover, the closer the cargo processed in a task to airside, the more obvious the knock-on delay will be, due to the previous flight. Especially for the case due to late arrival of flight, by changing the sequence of cargo processing for different types of cargos in a flight according to their inventory cost, inventory cost can be efficiently reduced. In peak hours, if the capacity of any task is increased, the waiting time of the task can be reduced, which unavoidably prolongs the waiting time of the next task. The waiting time is approximately equal to that saved time. Furthermore, if the capacities of every task are expanded simultaneously, the smaller the original capacity of a task, the longer waiting time of the task will reduce. The results of this study can serve as references for cargo terminal operators in improving cargo processing.