TRB¿s National Cooperative Highway Research Program (NCHRP) Report 615: Evaluation of the Use and Effectiveness of Wildlife Crossings explores development of an interactive, web-based decision guide protocol for the selection, configuration, and location of wildlife crossings.

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.

At head of title: National Cooperative Highway Research Program.

The objective of this study was the development of criteria and design procedures for the use of aggregate riprap linings, which consists of a layer of discrete fragments of rock of sufficient size to resist the erosive forces of the flow. The design of such riprap-lined drainage channels involves the interrelationship between the discharge, the longitudinal slope, the size and shape of the channel, and the size distribution of the riprap lining. This report describes these interrelationships and develops design criteria by which a riprap-lined drainage channel can be proportioned and the riprap lining can be specified for a given discharge and longitudinal slope. The relationships so developed have been reduced to design charts, the use of which permits rapid and simple establishment of channel shape and size as well as of the properties of the riprap lining.

This report contains guidelines and recommendations for managing and designing for friction on highway pavements. The contents of this report will be of interest to highway materials, construction, pavement management, safety, design, and research engineers, as well as others concerned with the friction and related surface characteristics of highway pavements.