Notice

This document is disseminated under the sponsorship of the department of transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof. This report does not constitute a standard, specification, or regulation.

The United States Government does not endorse products or manufacturers. Trade and manufacturers’ names appear in this report only because they are considered essential to the object of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in amanner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of itsinformation. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.