Review of international design speed practices in roadway geometric design.

Use of the classical design speed concept as a criterion for alignment consistency on rural highways originated in the United States in the 1930s in response to increasing accident rates at horizontal curves. As design practice and driver behavior have evolved, the concept has lost effectiveness at producing consistent alignments. The objective of this paper is to assess how design speed is being used in the United States and other countries internationally. Both a review of current design policies and a survey of transportation professionals from 18 countries were used to develop the evaluation.