Acknowledgments

U.S. Department of Transportation

Mary E. Peters
Secretary

Vice Admiral Thomas V. Barrett
Deputy Secretary

Research and Innovative Technology Administration

Paul R. Brubaker
Administrator

Bureau of Transportation Statistics

Steven D. Dillingham
Director

Produced under the Direction of:

Deborah Johnson
Assistant Director for Transportation Analysis

Project Manager

Long X. Nguyen

Contributors

David Chesser
Chester Ford
Xiaoli Han
Getachew Mekonnen
William Moore
Lorisa Smith
Charles Tennyson
Alpha Glass Wingfield
Jie Zhang