Sustainable Transit Bus Systems. A Focus on Traction Technologies 2011-36-0011
The increasing demand for urban mobility, combined with the constriction of investment capacity of transit authorities and private companies make bus based systems a great option for public transport systems, since they allow the provision of high quality services at a fraction of the costs of rail based systems. In this scenario, Bus Transit System - BTS and Bus Rapid Transit - BRT allow the implementation of transport networks at considerably lower costs than their rail system counterparts. This is specially true to developing-nation cities, that have infrastructure costs as a pre-eminent decision-making factor in technology selection. From an environmental perspective, traction technology and fuel option are decisive to define systems' performance. Unlike rail based systems, that are generally electrified, bus based systems allow the use of a variety of traction options, like Diesel and Otto engines, Trolleybus, Hybrid (Diesel-Electric) and Fuel Cell Engine as well as fuels, like diesel, low sulfur diesel, natural gas, biodiesel, ethanol, hydrogen and electricity, each option presenting its own operational and environmental performance trade-offs. The prime objective of this paper is to present the potential of bus based technologies from a capacity and performance perspective, showing some examples of BTS and BRT systems around the world and a review of traction technologies and their performance, followed by some bus system experiences, focusing on traction technologies strategies and their economical approaches, including both retrofitting and upgrade programs. This study is structured in a way that it presents the state of art technologies, followed by some case studies around the world. Finally, Life Cycle Analysis is performed in order to allow an evaluation from a technical-economical perspective. This work is supposed to be a technical reference to those involved in planning or operating bus based systems.