About the Authors

Kai Wang

Contributed equally to this work with: Kai Wang, David M. Levinson

Affiliation Beijing Key Laboratory of Traffic Engineering, Beijing University of Technology, Beijing, China 100124

David M. Levinson

Contributed equally to this work with: Kai Wang, David M. Levinson

dlevinson@umn.edu

Affiliation Department of Civil, Environmental, and Geo- Engineering, 500 Pillsbury Drive SE, Minneapolis, MN 55455, United States of America

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: DML KW. Performed the experiments: KW. Analyzed the data: DML KW. Wrote the paper: DML KW.