As part of its continuing assessment of advanced light-duty automotive technologies to support setting appropriate national greenhouse gas standards, the Environmental Protection Agency (EPA) has been acquiring fuel efficiency data from testing of recent advanced automotive technologies. This paper present EPA’s work to model and develop controls for a parallel P0 48V Belt-Integrated Starter-Generator (BISG) mild hybrid and a P2 48V inline on-axis configuration mild hybrid electric vehicle (MHEV), using the Gamma Technology GT-Suite vehicle model and the Matlab/Simulink/Stateflow tool. These models will be eventually integrated into EPA’s vehicle simulation model (ALPHA). The MHEV model was validated using data collected from a 2013 Chevrolet Malibu Eco 15kW 115V P0 BISG MHEV, obtained from Argonne National Laboratory (ANL) chassis dynamometer tests. The simulated fuel economy, engine torque/speed, motor torque/speed, engine on-off controls, battery voltage, current, and State of Charge (SOC) were in good agreement with the vehicle test data on a number of drive schedules. The 48V P0 MHEV electrical model was developed by updating 12/15kW BISG motor efficiency maps, 48/12V DC-DC converter and an electric circuit battery model with 48V lithium-ion battery pack test data into a calibrated 115V MHEV model. The 48V MHEV will be further validated with 48V MHEV test data in the future. The 48V P0 MHEV model was extended to 48V P2 inline on-axis configuration by adding two K0 and K1 clutches and a 20~25kW traction motor for further sensitivity analysis.