Narrow Tilting Vehicles (NTVs) have been proposed as a solution to traffic problems such as congestion and limited parking spaces. However, their small footprint can lead to a reduction in postural stability. To address this issue, NTVs have been designed to reduce the lateral acceleration experienced by occupants by tilting the vehicle body inwards during turns, depending on the driving situation. Three types of tilt control methods have been proposed for NTVs: direct tilt control (DTC), steering tilt control (STC), and combined steering and direct tilt control (SDTC). In this study, we proposed a simplified method to control SDTC using a single roll directional motion equation, focusing on the yaw angular acceleration and roll inertia of the vehicle body. The proposed method was found to result in a 84% reduction in the lateral acceleration experienced by occupants during turning maneuvers in the evaluation of real-vehicle dynamic tests.