Karekla, X; Fernandez, R; Tyler, N; (2018) Environmental Effect of Bus Priority Measures Applied on a Road Network in Santiago, Chile. Transportation Research Record: Journal of the Transportation Research Board , 2672 (8) pp. 135-142. 10.1177/0361198118784134.

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Abstract

Air pollution is at the highest levels ever and there is currently a worldwide initiative by transport engineers and urban planners to redesign public transport modes and cities to become more sustainable and environmentally friendly. The environmental impact of everyday activities is more apparent in developing cities which take longer to adapt to advanced methods of running public transport modes. This study aims to investigate the reduction of bus energy consumption and carbon emissions through bus priority measures in a bus route in the city of Santiago, Chile. Two bus priority schemes are tested in this study: Bus Only Lanes and Bus Signal Priority. The microscopic traffic simulator TSIS-CORSIM is used to quantify the environmental impact of these schemes. The results have shown that both schemes lead to lower fuel consumption and emissions, especially for the bus service. The environmental improvements are mostly apparent at traffic flows below 1000 veh/h, with clear benefits for both the bus service and passenger cars when dedicated bus lanes are included in the road infrastructure. Air pollution is an environmental phenomenon which puts a burden on people’s lives and affects everyday activities. Especially in urban metropolises, where more than half of the global population is accommodated, and more than 70% of the world’s carbon emissions are recorded. The world’s 10% richest people alone emit 50% of the worldwide greenhouse gas (GHG) emissions. These statistics show that the activities undertaken in cities are harming the environment and there is a clear need for changing our habits in the way we attempt everyday activities. It is essential to find ways to reduce air pollution and climate change whilst preserving people’s health and improving their wellbeing. One of the greatest GHG emitters in urban environments, with documented effects on air pollution, is transport systems. Transporting people and goods is a vital activity in cities, however energy related emissions from transportation amounts to 25% of GHG emissions worldwide. For reference, in 2015 the transportation sector in Europe emitted 26% of the world’s GHG and the USA emitted 27%. Transportation related emissions in China doubled between 2000 and 2010 and an extra 54% increase is expected up to 2020. Road transportation, in particular, is considered to be responsible for 70% of all GHG emissions, making it the largest polluter of all transport modes. As an example from the Latin American context, in Chile, 28% of the GHG emissions are generated by the transport sector, with private cars gaining ground over public transportation year after year, the levels of GHG emissions are constantly increasing. Indicated by 45% of GHG emissions from transportation in Chile being produced by cars and taxis, 10% by buses, and 1% by trains. In transport economics, road pollution is considered to be an abuse of the road that has been provided, whilst other users on the street are passive victims (1212 Button K. Transport Economics, 3rd ed. Edward Elgar Publishing Ltd, Aldershot, Hants; Northampton, 2010, p. 528.View Full Reference List). Therefore, it is necessary to provide alternative means of transport, such as public transport modes, as well as to improve the existing ones so that people stop the abuse of roads and start favoring environmentally friendly means over their private cars. Enabling people to choose more sustainable means of transport for their everyday mobility could significantly contribute to the reduction of GHG emissions worldwide. In regard to energy consumption, urban areas consume up to 75% of global energy, the majority of which is absorbed by the transportation sector. In 2010, transportation systems around the world consumed 19% of global energy supplies, 69% of which was consumed by road transportation. This number is expected to grow rapidly, and by 2050 transport energy consumption is expected to reach an 80% increase. In other words, by 2050 30% of the global energy will be channeled toward transportation, with the highest demand arising from developing countries and areas undergoing strong economic and population growth, such as Latin America and China. Statistics concerning car ownership rates highlight the global need to increase the attractiveness of public transport modes and to invest in energy efficient transport systems; car ownership in China has been growing by 12% per year, by 1.6% per year in the US, whereas only a slight increase in vehicle ownership is expected for European countries that are members of the Organization for Economic Cooperation and Development (OECD-Europe) by 2050. Bus priority schemes have been widely tested in various environments, such as in Japan, the UK, and Canada, with the aim to reduce traffic congestion, to improve bus journey times and road safety (examples are included but not limited to 15–17), but their environmental effect is still being explored. To tackle the environmental challenges discussed above, the main objective of this study is to examine how bus priority schemes may reduce energy consumption and carbon emissions. It focuses on the bus system in Santiago, Chile, and with the use of the microscopic traffic simulator TSIS-CORSIM, the current road network and bus system is replicated. Two bus priority schemes—Bus Only Lanes and Bus Signal Priority—were tested during the morning peak period. The collection of data, the model parameters and the examined bus priority schemes are described in the methodology section. The results obtained for energy consumption and emissions for each of the schemes are presented in the results section for both the cars and the bus system. The results are then discussed and the traffic flow and bus priority scheme for which the highest environmental improvement is achieved is proposed.

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