The Intersections Joint Subcommittee has an online manual that provides state of the art guidance on unsignalized intersections.
TRBs National Cooperative Highway Research Program (NCHRP) Report 650: Median Intersection Design for Rural High-Speed Divided Highways explores common safety issues at median intersections on rural divided highways, and examines innovative geometric and operational treatments for addressing those issues. The report includes ten case studies that illustrate how various treatments have been applied in the field.
This report presents recommended improvements for the geometric design and safety performance of at-grade intersections on expressways. In general, the operational and safety performance of these multi-lane divided highways nearly matches those of rural interstates. However, because expressways allow for stop-controlled at-grade crossings, increases in both major and minor roadway traffic volume have had a significant impact on intersection safety in recent years. The study investigated alternate safety improvements and indentified their relative effectiveness and focused on reduci