A yellow light is about all the latest federal study gives current proposals for high-speed passenger trains in various parts of the country. The recently released report - US Passenger Rail Technologies - was prepared by the Office of Technology Assessment (OTA), the technical research arm of Congress.
In the 1960s, the Japanese initiated high-speed passenger rail service with their famous ''bullet trains.'' In the 1970s, the British followed with a more conservative plan to provide 125-mile-per-hour passenger trains using existing track and conventional diesel locomotives. And three years ago the French inaugurated their high-speed TGV service between Paris and Lyon. In addition, the Japanese and West Germans have been working on methods to push train speeds to more then 250 m.p.h. by suspending (or floating) cars above the track magnetically.
Meanwhile, there has been no similar effort in the United States. A federal research effort into magnetic levitation was short lived. And intercity passenger rail traffic has continued to decline.
Despite this, there are a number of private and state-sponsored initiatives to introduce high-speed rail in various parts of the country, including California, Florida, Michigan, New York, Vermont, Nevada, Wisconsin, Ohio, Pennsylvannia, and Texas. Also, a Midwest Rail Compact of states has been formed to investigate an interstate network.
''These efforts are being promoted, in part, by US and foreign firms that might undertake corridor development or supply the technology. Some advocates of these ventures have suggested some form of federal assistance will be needed, while others claim none or very little will be required,'' the report states.
OTA researchers investigated the foreign experience with high-speed rail transport to see if this could shed any light on the accuracy of these claims.
Japanese and European high-speed trains are located in highly populated areas , they point out. In fact, only the Boston/New York/Washington area has comparable population densities.
Also, in Japan and France, conventional train systems were running at full capacity before high-speed service was instituted.
And all such services have been built with direct government assistance.
The Japanese approach of building special, high-speed track is particularly expensive - as much as $40 million per mile.
In the US, such a system ''would have difficulty generating sufficient revenues to pay entirely for operating and capital costs,'' the report concludes.
Both the major public benefits and potential costs of such trains depend critically on how many riders it would attract, the OTA observes. Enhancing regional growth, reduced highway congestion and air pollution, energy efficiency , and improved transportation safety all require large ridership. On the other hand, large ridership would harm competing forms of transportation while poor ridership would create a necessity for government subsidy.
Also, federal support for a successful high-speed train in one region would raise serious political questions of regional equity.
So, should Congress decide to support the idea, a major research effort designed to predict likely ridership would be needed.
National pride, and a desire for modern rail service, appear to sway the public in favor of these proposals. But, reading between the lines of the cautiously worded OTA document, the message is clear: Unless approached with extreme caution, high-speed rail could easily turn into a costly and inefficient boondoggle in the US setting.