This chapter aims to provide a comprehensive review of the latest low emission propulsion vehicles, particularly for bus applications. The challenges for city bus applications and the necessity for low emission technologies for public transportation are addressed. The review will be focusing on the London bus environment, which represents one of the busiest bus networks in the world. The low emission bus applications will be analysed from three main areas: hybrid electric buses, battery electric buses and fuel cell buses.This summarises the main technologies utilised for low emissions urban transportation applications. A comprehensive review of these low emission technologies provides the reader with a general background of the developments in the bus industry and the technologies utilised to improve the performance in terms of both efficiency and emission reduction. This will conclude with a summary of the advantages and disadvantages of the three main technologies and explore the potential opportunity of each.