This paper reviews highway alignment design policies and practices in a sample of countries throughout the world. The goal is to broaden our understanding and perspective of alignment design by highlighting similarities and differences between design philosophies and quantitative guidelines. It is hoped that accomplishing this goal will stimulate the continued improvement of highway geometric design. The information presented in this paper combines and builds upon recent studies in the United Kingdom, United States, and Germany that included reviews of alignment design policies and practices in a sample of countries. It was generally observed that there are many similarities in fundamental alignment design principles and philosophies and in quantitative guidelines on basic design parameters. These similarities may reinforce the reasonableness of countries' guidelines that fall within the norm of worldwide practice. What may be most interesting and important, however, are differences in policy emphasis and concern that have led to more advanced guidelines on certain geometric elements, and differences in local conditions and experience that have led to deviations from apparent worldwide norms for certain quantitative guidelines. It is the intent of this paper to gain insight by understanding the reasons for differences rather than to make judgments about deviations from the norm. Some countries combine their policies for rural and urban streets, whereas other countries have separate policies. This review focuses on alignment design for rural roadways. The review is divided into two major sections: first, a qualitative comparison of alignment design philosophies; and second, a quantitative comparison of design guidelines. The paper concludes with general observations about worldwide alignment design policy and practice.
Samenvatting