There are two types of technical development in railways. One is to promote basic researches first that will be applied to attaining a target at a later stage. The other is to set a specific target in advance, for which basic researches are carried out and element technologies are developed.

    A typical case of the latter is the development of Tokaido Shinkansen. In the past, it took six hours and 30 minutes for EMU express trains to run from Tokyo to Osaka at the maximum speed of 110km. To cut the travel time between these two cities to three hours, a target was set to develop a new railway system to run trains at the maximum speed of 210km, for which the development of element technologies and basic researches started in concert in the fields of track, rolling stock, power supply and other related areas. This eventually led to the advent of Shinkansen. In contrast, the former is related to comparatively small-scale development. Therefore, there are few cases of such unobtrusive developmental activities. This suggests that it will lead to a better achievement, if research and development are promoted under a preset target in the railway industry.

    Irrespective of whatever approach may be taken, however, it will entail more hardships in putting the result of development into practical use than in developing a new technology in the field of railway. Railways are inherently competing with other transport modes with safety and reliability as its most important selling points. In introducing new technologies, the demerit of failure seems to be magnified for promoters of railway operation rather than the merit of success. They don't feel assured even with a total system that integrates different technologies verified in the field, let alone technologies confirmed only through tests. To put the result of development into practical use, it is essential for developers and users to trust and cooperate with each other.

    Of course, successful technologies are proven for practical use through sufficient risk management. There are some cases, however, where risk management is not systematically implemented or it entirely relies on the perception of individuals. Although it is seen only in limited cases, technological development is sometimes promoted purposelessly, on small scales or for applications not directly related to train operation, in particular. In some cases, troubles fortunately don't occur or risk is too small to cause one. Fortune doesn't always smile, however.

    About 20 years ago, the author participated in a project to construct subway stations with a shield machine of special configuration. In those days, the shield tunneling method used shields of circular profile. In contrast, the project intended to bore an eyeglass-shaped tunnel in a stretch to a cross-section composed of two circles which partly overlapped each other, before lining was executed. It was an extremely fanciful tunnel in shape at a glance. In actuality, however, this construction method was to combine a number of proven technologies to involve little risk as a system.

    To convince conservatives, the author evaluated the risk of the new method by implementing tests and analyzing the troubles in the past, modified the plan and adopted supplementary devices against the conceivable risks that should be avoided. The author also documented the potential risks of small possibility or influence and those that could be coped with after occurrence. However, there are risks that cannot be evaluated unless the system in consideration is actually used. It determines the practicality of the result of technical development how to address this problem. In this case, the author judged that it was possible to remodel the tunneling machine on a large scale underground in case a risk had surfaced and additionally adopt a supplementary tunneling method without delaying the schedule of construction, though the construction cost would increase to a certain extent. As a result, the author was able to dash forward to put the new technology into practical use.

    Fortunately, this project was successful. It is still open to anybody's guess, however, whether the judgment was appropriate, or whether it was a brave or reckless deed. Triggered by the success of this eyeglass-shaped tunnel construction method, a number of technologies have been developed for the shield tunneling method and applied to practical purposes since then, with some falling in trouble. It will be instructive to know to what extent risk management was performed preliminarily in these unsuccessful cases.