The purpose of this manual is to provide clear and helpful information for maintaining gravel roads. Very little technical help is available to small agencies that are responsible for managing these roads. Gravel road maintenance has traditionally been "more of an art than a science" and very few formal standards exist. This manual contains guidelines to help answer the questions that arise concerning gravel road maintenance such as: What is enough surface crown? What is too much? What causes corrugation? The information is as nontechnical as possible without sacrificing clear guidelines and instructions on how to do the job right.

TRB's National Cooperative Highway Research Program (NCHRP) Report 672: Roundabouts: An Informational Guide - Second Edition explores the planning, design, construction, maintenance, and operation of roundabouts. The report also addresses issues that may be useful in helping to explain the trade-offs associated with roundabouts. This report updates the U.S. Federal Highway Administration's Roundabouts: An Informational Guide, based on experience gained in the United States since that guide was published in 2000.

This manual provides direction for the preparation of noise and vibration sections of environmental documents for mass transportation projects. The manual has been developed in the interest of promoting quality and uniformity in assessments. It is expected to be used by people associated with or affected by the urban transit industry, including Federal Transit Administration (FTA) staff, grant applicants, consultants and the general public. Each of these groups has an interest in noise/vibration assessment, but not all have the need for all the details of the process. Consequently, this manual has been prepared to serve readers with varying levels of technical background and interests. It sets forth the basic concepts, methods and procedures for documenting the extent and severity of noise impacts from transit projects.