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modeled to reflect the impacts upon traffic flow patterns. For the 2008 Kittitas County <br />model, VISUM calculates node capacities using the following node equation: <br />Node Capacity= Kl+ K4 * (Entering Link Capacity) <br />Node capacities for the Kittitas County model use the Kl and K4 constants. K4 was <br />used to simulate the effect that a green time-to-cycle length (G/C) ratio has at an <br />intersection. For modeling purposes, it was assumed that when similar link types <br />classes meet, the G/C ratio is fairly even, and as the roadway meets lesser class <br />roadways, the green time, or G/C ratio increases on the major facility. This effect is <br />reflected in the increasing values of the K4 constant as the difference in entering link <br />types or classifications is more disparate. When there are less than three (3) intersection <br />legs, the K4 constant is increased by .05 to reflect the impact of a smaller number of <br />conflicts. When there are five (5) or more intersection legs, the K4 constant is decreased <br />by .05 to reflect the impact of more conflicts, which take green time, at the intersection. <br />For shape nodes of Type 1 and Ramp Diverge nodes of Type 5 a K4 value of 1.0 should <br />be used. <br />Special Delay Links (SDLs) <br />Another special feature in VISUM (and prevfously in TMODEL) is the ability to model <br />intersections under STOP or YIELD control. SDLs at a node denote which link(s) are <br />under two-or three-way STOP or YIELD control. If an intersection is a four-way STOP, <br />then no SDLs are entered. SDLs are coded using the node dialog box with the TModel <br />tab. <br />Numb"l 131606265 <br />Link.a with tun ~dance al ToNode <br />~•OO)l;il:.7(1 •~ <br />-• ) 92942267(13154433,t <br />• <br />181 <br />181 <br />• <br />I or l !concei J <br />Kittitas County, Washington Transportation Model-May 2009 Page 19