台灣經濟快達成長，道路交通網路日益發達，公路之汽車貨物運輸業已成為主要之內陸貨運工具。但長期以來國內有關公路汽車貨物運輸業成本結構及相關問題之研究分析幾告闕如，因此本研究以較彈性化之Translog成本函數型態建立汽車貨運業與汽車路線貨運素之成本函數，並進行相關經濟指標之分析，並進一步檢討政府相關管制政策及費率訂定之合理性。本研究以民國86年之汽車貨運業(整車)斷面資料及民國的80-86年八家汽車路線貨運業(零擔)之經緯資料4進行實證分析，分析主要結論如下：1.造成台灣汽車貨運業成本結構不同的主要因素為平均載運長度(營運範圍)，而非如國外之貨運收入或產出，故本研究依據平均載運長度將汽車貨運業區分為短程、中程與長程運輸官司。2.汽車貨運索與汽車路線貨運業都具有密度經濟或輕微密度經濟。3.油料價格變動對汽車貨運業成本影響最大，勞動價格變動則對汽車路線貨運業成本影響最大。4.汽車貨運業與汽車路線貨運業都具有載運長度經濟與載運噸數經濟(但前者中之中程與長程運輸官司載運長度經濟較不明顯)，表示業者應提高載運長度與載運噸數。5.由汽車貨運素之密度經濟、邊際成本與平均成本關係發現法定運價高於均衡運慣，導致業者削價競爭，建議政層對於汽車貨運業費率管制應予解除。6.汽車路線黨雖屬於寡占市場，但僅具有輕微密度經濟，因此費率管制可採核備制，由主管機關接准上限價格，給予業者經營彈性。

The rapid economic growth and increase in highway investment in the past few decades have resulted in significant development of motor carrier industry and made it the most dominant inland freight transportation mode in Taiwan. Unfortunately, the cost structures of both domestic Truckload(TL) and Less-Than-Truckload(LTL) motor carriers in Taiwan have never been carefully investigated. Therefore, this study aims to develop a flexible translog cost functions for these carriers and to analyze their economic characteristics (ex. economies of density, elasticity of output, elasticity of input price, average cost and marginal cost). With these economic characteristics, we can interpret the current situation of the TL and LTL markets; moreover we can examine if regulated policies made for two carriers are suitable.Empirical analyses were performed using 1997 cross-section data for TL motor carriers, and the panel data(1991-1997)for LTL motor carriers. The major findings include: (1) The main factor causing the significant difference in the cost structure for TL is average length-of-haul, rather than total revenues or tonnage carries as in other countries; (2) TL has economies of density” while LTL has only weαk economies of density; (3) Among factors of input, fuel price has the most significant influence on TL’s cost, while labor price on LTL’s; (4) Both LTL and TL have evidence of economies of load size and length-of-haul (but only short haul TL has significant economies of length-of-haul); (5) The regulated price of TL is found to be higher than the equilibrium price from the analysis of their density economies, marginal cost and average cost. This has led to the cutthroat price competition among TL carriers, and so the price of TL should be deregulated; (6) Since LTL has only weak economies of density, A price ceiling with considerable downward flexibility in fares policy can be used.