The researchers studied how hybrid electric vehicles (HEVs) can help reduce pollution and improve fuel efficiency compared to regular cars. They looked at different types of HEVs and tested their performance using a vehicle simulator. The tests showed that HEVs emit less pollution and can be more energy-efficient than traditional cars. The results also highlighted that power converters play a vital role in HEV design, ensuring the electric motor works effectively. The study compared a regular car with a gas engine to series and parallel HEVs in different driving conditions. The tests demonstrated that HEVs are a promising solution for cutting emissions and making transportation more sustainable.