Enhanced Modeling of Left Lane Line Extensions for Permitted Left Turns in Skewed Intersections

This technical note, focusing on the competitive behavior of permitted left turns, introduces an enhanced model to determine the form of left lane line extensions, specifically designed to be applicable in skewed intersections with various angles. These left lane line extensions are composed of two straight lines and one circular curve, and are strictly constrained by the entering point, exiting point, and controlling point. Moreover, the model incorporates an adjustment mechanism for the left-turning stop line when the turning radius fails to satisfy the minimum requirement. A step-by-step procedure of designing left lane line extensions is provided, demonstrated with an example problem. This technical note offers traffic engineers practical guidelines for designing left lane line extensions in skewed intersections, prompting left-turning vehicles to yield to opposing through traffic and thereby improving traffic operations within the intersection.