This information was prepared as part of NCHRP Project 14-19, National Cooperative Highway Research Program.

SPECIAL NOTE: This report IS NOT an official publication of the National Cooperative Highway Research Program, Transportation Research Board, National Research Council, or The National Academies.

The opinions and conclusions expressed or implied are those of the research agency that performed the research and are not necessarily those of the Transportation Research Board or its sponsoring agencies. This information has not been reviewed or accepted by the Transportation Research Board Executive Committee or the Governing Board of the National Research Council.

Acknowledgments

The NCHRP is supported by annual voluntary contributions from the state Departments of Transportation. The work was guided by a technical working group that included:

Timothy J. McGrath, Simpson, Gumpertz & Heger, Inc.

Michael Fazio, City of Bluffdale, Utah

Cecil L. Jones, Diversified Engineering Services, Inc.

Michael G. Katona, Washington State University (retired)

Thomas P. Macioce, Pennsylvania Department of Transportation

Larry Ritchie, Florida Department of Transportation

John Schuler, Virginia Department of Transportation

Arthur P. Yannotte, CHA Companies

Waseem Dekelbab, NCHRP Senior Program Officer

Stephen F. Maher, Transportation Research Board Liaison