Improved methods for distribution of superelevation
thesisposted on 08.06.2021, 12:38 by Udai Hassein
The American Association of State Highway and Transportation Officials (AASHTO) provide 5 methods for distributing highway superelevation (e) and side friction (f). Method 1 (linear) is inferior to Method 5 (curvilinear). AASHTO Method 5 deals with speed variations, but its complex mathematical calculation affects design consistency. Safety margin is the difference between design and maximum limiting speed. This thesis describes distribution of superelevation (e) and side friction factor (f) based on the EAU and SAU methods using AASHTO and two different curves from the unsymmetrical curve; the equal parabolic arcs "EAU Curve" and a single arc unsymmetrical curve "SAU Curve". The thesis also describes e and f distributions based on the optimization model. The EAU and SAU methods and Parametric Cubic Optimization Model improve highway design consistency based on safety margins. Examples show the methods and optimization model are superior to AASHTO methods.