resources, all responses to questions were accepted at face value unless obviously incorrect and in such instances were not included. The assumption was made that those individuals assigned by their respective firms were responsible and knowledgeable about the data they were providing. In the interest of time it was necessary to establish a deadline for returning the questionnaires. Some questionnaires were returned well after this deadline and were received after this analysis had been completed. For example, one major firm which projects 2,350 carloads of freight during 1977 returned its questionnaire a full two months after the deadline and could not be incorporated. Therefore, it should be understood that this survey represents a partial survey.