One configuration of a hybrid electric vehicle (HEV) is the split-axle parallel architecture, which enables existing vehicles to be retrofitted into a hybrid vehicle with minimal modification - achieved by placing electric motors in the hub of the otherwise non-driven wheels. The present work describes different HEV configurations and identifies specific operating modes of the split-parallel architecture. Coupling of the two power sources - internal combustion engine (ICE) and electric motor - and control system configuration for the split-parallel hybrid are also presented. Proper distribution of power between the two sources determines effective operation of the hybrid vehicle. The control problem consists of determining this power split at each instant of time. The target is to achieve minimum consumption of fuel, while ensuring the state-of-charge (SOC) of the battery bank remains at acceptable level. This paper reviews some of the control strategies for the HEV, which can be investigated on the split-parallel configuration. Finally, development of a prototype of the split-parallel hybrid vehicle with in-wheel motors - retrofitted from a conventional vehicle - is described. © 2012 IEEE.