There are three equivalent procedures to evaluate the voltages induced by lightning on power lines, namely, the Agrawal–Price–Gurbaxani model, the Taylor–Satterwhite–Harrison model, and the Rachidi model. The Cooray–Rubinstein approximation is a procedure used by scientists and engineers to estimate the horizontal electric field from the lightning that is used in the induced voltage calculations for lines located over a finitely conducting ground. The Cooray–Rubinstein approximation is usually incorporated in calculating the induced overvoltages using the Agrawal–Price–Gurbaxani model. In this article, it is shown how this approximation could be incorporated into the other two coupling models. The resulting coupling equations are compared to each other by calculating the voltages induced on two idealized overhead transmission lines.