The aim of signal coordination control is minimization of delay and stop at each intersection. In the simple case that one link between two intersections; the authors have organized the theory of coordination effect under the condition of the same green split and any value for the two intersections. However, the case that different green splits for two intersections has not discussed. The theory under the condition of maximum under-saturated demand for any green splits is discussed in this paper. The major findings are; 1) the link length to maximize coordination effect is identical under same green split with any split value, and this characteristic of the length is the same for any green split conditions, 2) the link length to minimize coordination effect is different for the different same green split values for the two intersections, moreover the link length to minimize coordination effect is another value in the case of different green split values for the two intersections.