While most freight rail operators are aware of problems that affect reliability, the Association of American Railroads and the Massachusetts Institute of Technology have under way a study aimed at unearthing specific causes of those problems.

James R. Lundgren, special assistant to the AAR vice president of research and testing, said a 1989-90 study by Temple, Barker, Sloane of Lexington, Mass., found shipper complaints that railroad "service reliability falls down quite markedly in comparison with the trucking industry."In response to the findings, the AAR commissioned the MIT Center for Transportation Studies in 1991 to find specific root causes as to why railroad reliability falters. By year's end, that specific causal analysis will likely result in a prioritized set of ranges of impact the identified causes have on reliability.

Among issues the study is addressing is the just-in-time concept as it is used by bulk shippers, such as coal-burning electric utilities, compared to merchandise shippers such as automobile manufacturers, said Carl D. Martland, chief MIT study researcher.

Mr. Lundgren said the MIT research has a twofold goal: to help rail operators improve performance and to guide the AAR's own research, which has the same aim. The AAR expects a wide range of responses from individual rail carriers to any proposed solutions to reliability problems, Mr. Lundgren said, ranging from enthusiasm to "that's not for us."

The current study is actually a renewal of a 1971-81 study of railroad reliability, also done by the MIT center in conjunction with the AAR and Federal Railroad Administration.

Mr. Martland said the earlier work contributed to the nation's railroads' love affair with technology, improved planning and such nitty-gritty as improved dispatching, terminal control and locomotive and crew allocations.