A modal shift is an increase or decrease in the use of one or more modes of passenger or freight transportation at the expense of another or others. It can occur for several reasons, including changes in costs, technological advances, and public policy.
There has been growing interest during the past several decades in the use of mode shifting as a fundamental strategy for combatting the rapid deterioration of the earth's environment. This is because, while continuing advances in transportation technology and an ever-expanding transportation infrastructure have brought major economic and quality of life benefits, they have also been very largely responsible for the great environmental devastation that has been occurring.
For example, transportation powered by fossil fuels, mainly automobiles, trucks, buses and aircraft, accounts for about a quarter of carbon dioxide emissions, the second largest source after electric power generation, and is continuing to increase.1 The largest share is for automobiles, at nearly half, followed by trucks.
In response, there has been much emphasis recently, including legislation and large subsidies in a number of countries, on replacing conventional automobiles with electric automobiles as a means of reducing both greenhouse gas emissions and localized air pollution. However, numerous problems exist with this approach, and, in fact, it is not clear that it would actually provide any substantial net environmental benefit.2 Rather, it could just be a distraction — and an extremely costly one — from taking the difficult but urgently needed measures to effectively combat our rapidly deteriorating environment.
Shifting to much less harmful modes in combination with a reduction in the demand for mechanized transportation as a whole would be a far more effective solution. Such modes include rail and other public transportation, walking, bicycling, and, in some cases water transport. Rail can be particularly effective in situations where there are substantial passenger or freight volumes, primarily because of its very low energy consumption due to the low friction of steel wheels on steel rails.
Mode shifting can be promoted by a variety of means, broadly classified into improvements in alternative transportation modes (such as greater availability and frequency), financial incentives (including taxes and subsidies), regulatory changes (e.g., stricter emissions and fuel efficiency standards), and changes in land use policy (especially encouraging higher density development).
Some examples of successful mode shifting already exist. Often cited are the dramatic reductions in air travel that have occurred between pairs of cities in Asia and Europe as a result of the establishment of high-speed rail services between them.3 Also, there are a number of cases of the establishment of well-planned light rail systems in European cities resulting in reduced automobile usage, reduced air pollution, and a variety of other benefits.4
_______
1 See, for example, Lee Chapman, Transport and climate change: a review, https:// www.sciencedirect.com/ science/article/ abs/pii/ S0966692306001207
2 The argument for replacing fossil fuel vehicles with electric vehicles is based mainly on the hope that the vast amount of electricity required to recharge the batteries would be generated by non-polluting technologies. Unfortunately, most electricity is currently generated by the burning of fossil fuels and is likely to continue to be for years to come. Moreover, in many countries, including the United States, the electric power generation system is already operating at or near capacity and has little ability to accommodate a massive surge in electric vehicle use.
Construction of a sufficient increase in electric power generation capacity along with the necessary transmission lines and recharging facilities would not only be extremely costly but could also create much additional environmental degradation. Moreover, considerable damage is already resulting, particularly in some developing countries, from the large-scale mining of cobalt, lithium and other rare metals required for use in electric vehicles. Additionally, much of the pollution from road vehicles is in the form of particulate matter created by the abrasion of road surfaces by vehicle tires and of brake linings, and such pollution might actually increase because of the much heavier weights of electric vehicles.
3 See, for example, Zhenhua Chen, Impacts of high-speed rail on domestic air transportation in China, 2017, https:// www.ncbi.nlm.nih.gov /pmc/articles/ PMC7127363/
4 See, for example, Zaragoza: The perfect advert for modern LRT, 2018, Tramways and Urban Transit, http:// www.tautonline.com/ zaragoza-perfect-advert-modern-lrt/