A number of state railways over the world have experienced railway reform, and vertical separation has been frequently utilized during its process. This thesis investigated a variety of models of vertical separation, which the railway sector has experienced over the twenty years. The main aims of the research are clarifying the key issues on vertical separation: aims of the reform; forms and implementation; advantages; disadvantageous effects.

　The author chose the case study technique, and made the investigation mainly through interviews/questionnaires to the railway managers. Based on the examination into the selected cases, this study comparatively analyzed them in terms of: 1) separation of operational factors; and 2) separation of financial responsibilities. The study also tried to examine an appropriate form of railways depending on the market structure.

　There are a number of different forms of vertical separation, and the study clarified the characteristics of each type of it. It also disclosed that whether it intends to introduce within-rail competition or not largely outlines the form of railways. In case it is intended to introduce within-rail competition promoting new entry into the market, it leads to separate operational (at least slot-allocation) and financial responsibilities between infrastructure and operation, whereas without an intention to introduce it, coordination problems through vertical separation are endeavoured to be lessened through certain measures such as integrated operation, share-holding relationship, and confining the separation into the smaller market.

　The study showed that vertical separation has a number of advantages, and that the unique exclusive advantage of complete separation, such as the case in UK and Sweden, is introducing within-rail competition fostering neutrality even between the passenger and the freight. It also revealed that this form raises coordination problems even in the prime market especially on condition infrastructure capacity is limited. The result of the study leads to the conclusion that full costs and benefits should be considered upon introducing a form of vertical separation, and that the appropriate form of it depends on the circumstances as well as its objectives.

鉄道の上下分離についての一分析

　近年、多くの国鉄に改革が施されたが、その過程において多様な形態の上下分離が導入された。本論文は、多数の文献および各国の鉄道事業者への調査によって、上下分離の導入目的、形態、長所及び短所を明らかにした。さらに、多様な上下分離の形態を「運営面の分離」と「財務面の分離」という観点から比較・分析を行い、それぞれの形態の特徴を明らかにした。

　欧州における上下分離は、鉄道事業者間の競争の導入を特徴としており、競争を促進するために、財務面のみならずダイヤ設定など鉄道運営の重要な要素に関する責任も鉄道事業者とインフラ管理者との間で分離されている。本論文は上下分離の形態から派生している問題点を検証し、「競争導入による便益」が「分離による費用」を上回っている場合に限り、ＥＵ型の上下分離が有効であることを明らかにした。さらに、鉄道改革の目的と鉄道市場の特性に応じた適切な上下分離の形態を提示した。