At head of title: National Cooperative Highway Research Program.

The progress that has been made in developing the positive guidance concept is documented, and the meaning of positive guidance, the philosophy of driver performance upon which it is based the nature of the driving task at those locations where positive guidance is applicable, and a procedure for its application are discussed. This report describes what must be done to improve the information system at hazardous locations. Positive guidance which is an information system matched to the facility characteristics and driver attributes, is based on the premise that a driver can be given sufficient information where he needs it and in the form that he can best use to avoid hazards.

Expectancy relates to a driver's readiness to respond to situations, events, and information in predictable and successful ways. This report describes the concept of driver expectancy in the context of the driving task, and provides examples of expectancy and expectancy violations. It includes a procedure for identifying general and specific expectancy violations to enable engineers to develop remedial treatments to deal with expectancy problems.

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.