Impedance Effects of Left-Turning Vehicles from the Major Street at a Two-Way Stop-Controlled Intersection

At a two-way stop-controlled intersection without a turning lane on the major street, all three movements (right, through, and left) share a lane. To cover the effect of mutual impediments between these movements on the minor street capacity, the major street-shared lane equation, 17-16, is provided by the current Highway Capacity Manual (HCM 2000). This paper shows that this formula should be replaced by an improved equation to get more realistic results. This improved formula is derived. The theoretical concept can also be extended to include the consequences of a short turning lane on the major street. An equation is derived that calculates the effect of the length of the left-turn pocket on the capacity of minor movements.