Due to the consideration of fragile security, and longer check-in times and inconveniences due to increased air travel security examination since September 11th 2001, more and more people have turn to ground transportation. Unfortunately, the inefficient, environment-unfriendly and unsafe passenger cars and buses are the only choices available for middle distance trips. Development of high efficiency, clean and high speed railroad passenger transportation system has become more necessary to overcome this weak link. In this paper, the applicability of hybrid drive train technologies for middle-distance passenger train locomotives will be investigated. A systematic design of the diesel based hybrid locomotive helps to increase efficiency, improve fuel economy, reduce emissions and also reduce mass production costs. Furthermore, professional management and maintenance of railroad train locomotives make such new technologies more practical than for road vehicles. The success of such transportation system will have a great positive impact on our social activities, quality of life, energy supply, environment and economy. A diesel based hybrid electric locomotive (HEL) with batteries or an ultracapacitor is an option to reduce fuel consumption and emissions and provide better performance and fuel economy. The reduced fuel consumption helps reduce the amount of pollutants released. Engineering estimation indicate that emissions will be reduced by 70% and fuel efficiency will be increased by at least 30% in hybrid locomotives.