In this paper (Part IV of a series on “Wheel/Rail Noise”) analytical formulas for predicting wheel/rail rolling noise in urban rail transit systems are developed based on the characterization of the wheel/rail dynamic system developed in Part I and the roughness spectra on the running surfaces of the wheels and rails. Measured values of wheel and rail roughness spectra taken on an operating rapid transit system are used with these formulas to predict the rolling noise at the wayside. These predictions prove to agree well with published data on the wayside noise from that system. In addition, measurements of the wheel roughness spectra on a small personalized rapid transit (PRT) vehicle and the rail roughness spectra on a section of the test track for that vehicle, when used in the analytical formulas, yield predictions of the wayside noise during passage of the PRT vehicle that agree well with field measurements of that noise.