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.

The focus of this report is to develop policy recommendations guidelines, and policies for bicycle and pedestrian use of freeways expressways, tunnels, and toll bridges in California. Results from a survey and literature search are first presented. This is followed by an analysis of collision patterns for bicycles, freeway bicycles, and pedestrian collisions. The safety record of bicycles on bridges and in tunnels is then examined. A multivariate regression analysis of freeways open to bicycles and all freeway collision is described. The report concludes with recommendations addressing issues related to user education, data collection, age restrictions, shoulder geometry and procedures for allowing bicyclists to cross ramps.

This guide was written as a quick primer for transportation professionals and analysts who assess the impacts of proposed transportation actions on communities. It outlines the community impact assessment process, highlights critical areas that must be examined, identifies basic tools and information sources, and stimulates the thought-process related to individual projects. In the past, the consequences of transportation investments on communities have often been ignored or introduced near the end of a planning process, reducing them to reactive considerations at best. The goals of this primer are to increase awareness of the effects of transportation actions on the human environment and emphasize that community impacts deserve serious attention in project planning and development-attention comparable to that given the natural environment. Finally, this guide is intended to provide some tips for facilitating public involvement in the decision making process.