After the much too premature loss, earlier this year, of our greatly loved and admired colleague and co-editor of this journal, Prof. Ryuichi Kitamura, it was clear for the two of us that we would help to realize this tribute chosen by the editors—chosen to celebrate and honor his life and contribution to his field of study, but also and in particular his work for this journal. Ryuichi had been editor of Transportation since 1990, after earlier guest-editing a special issue on “Activity-based Travel Analysis: a Retrospective Evaluation and Some Recent Contributions” with the late Eric Pas and Frank Koppelman. Since then he assisted and supported a large number of authors in publishing their papers to the standards of the journal, and with this helped to define the style of Transportation and to build its reputation.

While his some 280 publications have appeared in many journals, it could be said that Transportation was his “home journal”. It is therefore entirely fitting that this special issue will be devoted to reprising work from Ryuichi’s own hand—excellent research that originally appeared in reports or in conference proceedings, and thus may not have achieved the visibility it deserves. Because of our criteria that the work (1) should not have been published in the readily accessible peer-reviewed literature and (2) should not have been largely superseded by later developments, these selections do not pretend to constitute a fully representative cross-section of Ryuichi’s contributions. Nevertheless, they do offer a broad view of the variety of topics he addressed and the methodological approaches he brought to his research. They were chosen in part because we believe them still to be of current interest.

Specifically, the six papers we selected address most of the key themes which engaged Ryuichi’s scientific curiosity and scholarship: the need for a dynamic, activity-based approach to analyzing travel behavior, the importance of values/attitudes, humans’ need to travel for its own sake (including seeing the automobile as an end in itself, as well as a means), the relationship between housing preferences and travel behavior, the endogeneity of car ownership, the heterogeneity of tastes and choice processes, the characterization of human activity space and the relevance of information and communication technologies. While the data sets used here are dated—the papers were originally presented between 1988 and 1998—their analyses still afford some important empirical benchmarks. The methodologies employed are creative and diverse, including novel applications of ordered and discrete response, Tobit, and structural equations models. His methods remain as fresh as ever and showcase his mastery of both the conceptual and the technical which made his work so important for travel behavior analysis.

The six papers are accompanied by a complete (we believe) list of Ryuichi’s publications, which was assembled with assistance from Ram Pendyala and from colleagues at Kyoto University. It is hoped that this list will help make his work accessible in a way which the search engines and databases cannot.

In addition, we are happy and very grateful that eight of his colleagues, who worked closely with him over the years, have contributed tributes which describe the man, the researcher, the teacher and the professional. These homages, together with Martin Richards’ tribute in a previous issue (Richards 2009), and those that have appeared elsewhere (e.g. Mokhtarian 2009), afford us a vivid and multifaceted picture of Ryuichi. This issue concludes with some parting words by Transportation’s Editor-in-Chief, Martin Richards.

Beverly Zumbühl, Barbara Hiltbrunner and Martina Koll-Schretzenmayr (all ETH Zürich) recreated and proofread the papers, including correcting some typographical errors in the originals. Oliver Schmid and Georg Roth (both ETH Zürich) produced the graphs where the scans did not yield publishable quality. Their support was crucial and is most gratefully acknowledged.

The papers are unaltered in their essence, but minor changes were made to meet the style of the journal, e.g. with respect to references or design of the graphs and tables. Citations that were in-press at the time of original publication have been updated. A few clarifications were required, which do not change the meaning of the text. Any substantive change (such as the addition of an abstract) is indicated with a footnote and was added only after discussions with any co-authors of the papers. Finally, we want to thank all of the co-authors and the publishers for their permissions to reprint the papers in this special issue.

We hope that this special issue invites us all to return to Ryuichi’s work, and to continue his rigorous scholarship which was devoted to a better and fuller understanding of human travel and its contribution to, as well as its impacts on, our individual and societal well-being.