At the end of “Cutting-edge transportation: Effective emissions-reductions approaches,” in closing, I wrote: “With that said, transit might just be the best thing going when it comes to mitigating negative environmental impact.” Well, time has come to expound upon that thought.
For starters it is helpful to clarify “negative environmental impact.” In the context of air quality it has to do with degradation of the air due to human influence. There are a number of emissions released into the atmosphere from many different sources. Among these are carbon monoxide (CO), greenhouse gases (GHG), nitrogen oxides (NOx), ozone (O3), particulates (PM 10 and PM 2.5), sulfur oxides (SOx) and sulfur dioxides (SO2), volatile organic compounds (VOC), etc.
Looking at one emission – carbon dioxide (CO2) – from the International Union of Railways’ High Speed Rail and Sustainability Nov. 2011 report, based on 2009 International Energy Agency (IEA) information, from all emissions sources in 2007, the transport sector’s contribution of CO2 worldwide is 23%.
Just to put things in perspective, electricity and heat contributes 41% CO2 worldwide with lesser amounts from industry (20%), residential (6%) and other (10%).
And then there was this qualifying statement: “Among all sectors, the transport sector is the only one in which emissions are continuing to increase in spite of all the technological advances. Moreover, transport emissions, for instance in Europe, increased by 25% between 1990 and 2010. By contrast emissions from the industrial and energy sectors are falling.”
“The alarming performance of the transport sector is largely due to road traffic, which accounts for 73% of global transport emissions… If domestic and international aviation is combined then it is the second largest emitter accounting for 13% of global transport emissions. By contrast, the rail sector accounts for just 2% of total transport emissions. …A modal shift from road and air towards rail is one obvious way to reduce CO2 emissions.”
So, by my suggesting “transit” (read: “rail”), “might just be the best thing going when it comes to mitigating negative environmental impact,” it would appear that I’m on the right track, at least with respect to CO2 emissions-releases, that is. And then again, all transportation-released pollutants considered, it should follow then that rail is the most environmentally friendly transport method going, regardless.