An empirically calibrated theoretical model is presented for the estimation of total approach capacity at signalized intersections with shared and short lanes. The model extends the theoretical capacity formula for shared and short lanes at unsignalized intersections (previously introduced by the author) to signalized intersections. The model accounts for the stochastic nature of traffic flow and the effect of queue blockage on the short turn lanes. The VisSim simulation package was used to generate a comprehensive database for model calibration under different lane and signalcontrol conditions. The proposed model can be used for arbitrary lane and signal-timing configurations. Explicit equations are given for signalized intersections with simple shared- and short-lane configurations. Detailed monographs are prepared for practical applications.