Intermodal Transportation: Results of GAO's Survey on Air-Rail Connectivity (GAO-13-692SP, August 2013), an E-supplement to GAO-13-691

Read the Full Report: Intermodal Transportation: A Variety of Factors Influence Airport-Intercity Passenger Rail Connectivity (GAO-13-691).


This e-supplement presents the results of GAO's web-based survey on air and intercity passenger rail (air-rail) connectivity. The survey asks selected experts for their views on questions about (1) benefits of air-rail connectivity, (2) strategies that could improve air-rail connectivity, (3) factors that facilitate and hinder the development and use of air-rail connectivity, and (4) differences between air-rail connectivity in the United States and Europe.

The survey was administered to 42 experts selected based on their knowledge of one or more of the following topic areas: intermodalism, airlines and the air travel industry, airport operations, the rail industry, and passenger travel. To select these experts, we collaborated with the National Academy of Sciences to identify 25 experts from the aviation and rail industries, Amtrak, state and local governments, academia, and the private sector. We identified 17 additional experts in these fields through a review of academic literature, our previous work, and interviews with other experts. We employed a modified version of the Delphi method to organize and gather these experts' opinions. The Delphi method is most commonly applied in a group-discussion forum. We modified the approach to have the group discussion take place in the form of a web-based survey. The survey was conducted in two stages. The first stage of the survey asked the experts to respond to five open-ended questions about various aspects of air-rail connectivity.

We received responses from 40 of 42 experts. We analyzed the responses provided by the experts and summarized the responses into categories to develop close-ended questions for the second stage of the survey. In the second stage of the survey, we asked each expert to evaluate the responses of the other experts using the summarized, close-ended questions developed from the first stage of the survey. We received responses from 41 of the 42 experts for the second stage of the survey. The information and perspectives that we obtained from the expert survey may not be generalized to all experts who have an interest or knowledge of air-rail connectivity issues. This e-supplement includes the questions asked and a summary of answers given for the second stage of the survey. Responses to open-ended questions, including those from the first stage of the survey, are not included in this e-supplement.

We administered the survey from January 2013 to May 2013 in accordance with generally accepted government auditing standards. A more detailed discussion of our objectives, scope, methodology, and agency comments on the draft report are contained in our report entitled Intermodal Transportation: A Variety of Factors Influence Airport-Intercity Passenger Rail Connectivity, GAO-13-691 (Washington, D.C.: August 2013).


Page Name Questionnaire Results
Introduction View View
Section I. Benefits of Airport and Intercity Passenger Rail (Air-Rail) Connectivity View View
Section II. Strategies to Improve Airport and Intercity Passenger Rail (Air-Rail) Connectivity in the United States View View
Section III. Factors That Facilitate and Hinder Airport and Intercity Passenger Rail (Air-Rail) Connectivity View View
Section IV. Differences between the United States and Europe Contributing to Variations in Their Respective Airport and Intercity Passenger Rail (Air-Rail) Connections View View


Gerald L. Dillingham, Ph.D., (202) 512-2834, or



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