This book is designed primarily as a text for junior, senior and fifth-year college courses in highway and transportation engineering. It is also a starting point for advanced courses and individual study in these areas. Furthermore, it summaArizes the state of the art and important new developments in transportation planAning and highway technology to assist practicing engineers, administrators, and other decision makers. This book can, in the main, be used by those who have very little background in technical engineering. However, some knowledge of route surveying, dyAnamics, and Engineering Fluid Mechanics is necessary for a complete understanding of cerAtain topics. These topics are included because they are important to more adAvanced students and to practicing engineers.For those who desire more detailed knowledge on specific topics, a substanAtial number of pertinent references have been cited. They include classics from the past and others giving recent findings.