1. Introduction

Possible global passenger transport futures are important to consider both because of the economic importance of this sector, and because of the environmental/social costs generated, many of which presently go unpaid. Before the 2020 pandemic, most forecasts were upbeat about the continued growth of global passenger transport. Pre-pandemic, the Organization of the Petroleum Exporting Countries (OPEC) forecast passenger car numbers growing from 1133 million in 2018 to 1969 million in 2040. In their late 2020 report, the OPEC forecast for 2040 had dropped slightly to 1936 million, but the 2045 forecast was for 2119 million passenger vehicles, with strongest growth in countries outside the Organization for Economic Cooperation and Development (OECD) [1]. For air travel, Airbus in 2019 forecast an average 4.7% annual growth globally out to 2038 [2].

Given the great inequalities in ownership of vehicles and plane travel throughout the world, it might be argued global passenger transport will continue to rise strongly as predicted by OPEC and Airbus, as presently low-mobility countries catch up with the OECD. However, present high levels of travel come at a high cost, not all of which is covered by users. Fossil fuels overall receive an estimated global subsidy of US$ 5.3 trillion in 2015 [3]. Much of this subsidy was for CO₂ emissions, including those from passenger transport. But passenger transport incurs a number of other costs: oil supply security fears; the global toll of road fatalities and injuries; air and noise pollution, especially in urban areas; the heavy uptake of urban land for transport infrastructure; and even the health implications from the lack of exercise caused by the replacement of walking and cycling by motorised modes.

Climate researchers sometimes speak of a ‘carbon pie’—the maximum allowable global CO₂ emissions to avoid serious climate change [4]. Many papers have discussed the equitable division of this ‘pie’ between the world’s nations or even individuals. This idea of limits has prompted Swiss advocacy of a ‘2 kW society’, in which Swiss average power use per capita is reduced to 2 kW by year 2050 [5]. Given passenger transport’s many costs—particularly CO₂ emissions—it might be time for high-mobility countries to analogously consider a ‘4000 p-k society’, with average vehicular travel levels per capita of 4000 passenger-km (p-k). (One passenger-km is generated when one passenger travels one km.)

2. Transport patterns: Past and present

In 1900, global vehicular passenger travel was only about 0.2 trillion p-k (tp-k)—see Table 1. Nearly all of this travel was by rail. Even given a nearly 5-fold rise in global population, a roughly 240-fold growth in travel from 1900 to 2018 is extraordinary, and has been termed ‘hypermobility’ [6]. In 1950, nearly all the world’s cars were found in North America; today, both car manufacturing and ownership is more evenly spread around the globe. Nevertheless, huge ownership inequalities persist, with the US owning over 700 light passenger vehicles per 100 population, compared with less than 20 in many low-income countries, especially in tropical Africa.

Table 1. Global passenger travel-related data 1900, 1950, 2018.

¹Author’s estimates. Sources: [1, 4].

Although in 1900, coal fuelled most of the world’s trains, by mid-century, oil-based fuels were dominant, with some electric traction for urban public transport. This oil dominance has continued to this day, despite increased use of natural gas (NG), bioethanol, and electric vehicles (EVs). Table 2 gives a percentage breakdown of fuels transport fuels, for both passenger and freight, for 1973 and 2018. Alternative fuels are mainly used by surface passenger transport. Transport, both passenger and freight, in 2018 used 29.1% of global final energy demand, compared with 23.1% in 1973 [7]. Transport’s share of energy-related CO₂ in 2018 was somewhat smaller, at around 24% [7].

Table 2. Global transport final energy demand by fuel, 1973 and 2018.

Source: [7].

Recent developments, however, cast doubt on the future of NG and biomass-based alternative fuels, as well as petroleum. Even though these fuels are still increasing their share, this situation may not last for much longer. A number of countries (and cities) plan to ban internal combustion engine vehicles, some as early as 2030, usually for air pollution reasons [8, 9]. The choices would then be between EVs and hydrogen fuel cell vehicles (HFCVs). Although at various times both have found favour, at present EVs have won out—at the end of 2019 they numbered 7.2 million (of which 47% were in China), compared with only a few thousand HFCVs [10]. The key advantage for EVs is the ubiquity of electric grids; batteries can be (slowly) charged from domestic power points. The global number of private slow chargers now number 6.5 million, public slow-charging stations about 0.6 million and public rapid-charging stations over 0.26 million [10].

Improvements in vehicular energy efficiency are often seen as an important means for simultaneously cutting oil use, and the resulting air pollution and CO₂ emissions, and large gains are theoretically possible [8, 11]. Although steady improvements have been made in vehicle engine efficiencies, for 20 OECD countries between 2000 and 2017, including the largest, no significant change in energy efficiency (MJ/p-k) occurred for light duty vehicles [7]. Reasons include the shift to larger vehicles, higher performance, and more energy used for auxiliary purposes such as power steering.

3. Future transport

Two decades ago, Schafer and Victor [12] forecast the world’s travel future out to 2050, mainly based on three assumptions. First, that on average people everywhere allocate roughly 1.1 hours per day for travel by all modes including non-vehicular travel. Second, that at least in high-income countries, travel expenditures form a roughly constant share of household disposable income. Third, that global real GDP would continue to grow at a constant rate. Given the three assumptions, it follows that total travel will continue to rise in line with total income, and that because of the daily travel time limit, faster modes would replace the slower ones. In short, car travel would replace non-motorised modes and surface public transport, and air travel (together with very fast rail) would replace long-distance surface travel. Unfortunately, faster modes are also more energy intensive [13].

The peak in per capita surface travel reported in a number of OECD countries and cities [14], together with the rapid growth in air travel provides some support for their approach. Their global-level forecasts for 2020 and 2050 were around 53 tp-k and 103 tp-k respectively [12]. The 2020 global estimate of 53 tp-k, may well have proved fairly accurate—were it not for the 2020 pandemic. Although their first two assumptions seem reasonable, the evidence is contradictory [15]. Further, no allowance is made for possible economic growth declines, or the need for transport to reduce CO₂ emissions. The conclusion is that—unlike planetary movements—future transport levels cannot be predicted; they are still very much open to policy interventions.

The global coronavirus pandemic, and the resulting lockdowns in many countries, caused a significant drop in travel compared with 2019. Air travel, especially international services, has been particularly hard hit. Nor does the International Air Transportation Association (IATA), forecast a rebound to business-as-usual anytime soon. The industry expects losses of US$ 118.5 billion in 2020, and US$ 38.7 billion in 2021. ‘Passenger numbers are expected to plummet to 1.8 billion (60.5% down on the 4.5 billion passengers in 2019). This is roughly the same number that the industry carried in 2003’ [16].

During the lockdown and travel restrictions in many countries, people who could work from home were encouraged or required to do so. Working from home with the aid of Information Technology has been discussed for decades, but has never been popular [17]. However, in 2020 it became the only option for many workers and students. Even before the coronavirus pandemic, some researchers were questioning the need for air travel, often because of its carbon footprint (see, for example [18, 19]). With on-line conferencing becoming common, its several advantages over conventional conferences are becoming clearer [20]. It is much cheaper: the virtual attendee saves on air fares and accommodation. This low cost has enabled more attendance from post-graduate students and those from lower-income countries. It also means that time-pressed individuals can attend from their own homes or offices. Finally, it gets around the problems of visa difficulties and travel bans because of pandemics or politics. Internet learning was also heavily used during lockdowns at all levels of education, and in the post-pandemic era, it seems likely that more work and (especially tertiary) education will be done from home compared with 2019.

Technical fixes are unlikely to solve passenger transport’s many challenges. As Table 2 shows, fossil fuels are being replaced far too slowly, and renewable energy may never be able to supply anywhere near present energy consumption levels [21]. Energy efficiency improvements are offset by the shift to less efficient, faster modes, by rising car ownership in non-OECD countries, and by energy rebound effects as fuel efficiency rises for a given mode. It may be that the observed replacement of travel by internet use will prove to be only temporary. Nevertheless, this large-scale global natural experiment did show that much travel replacement was possible; if for various reasons travel must be reduced, the internet could prove an important means of coping with reduced travel.

4. Conclusions

Before 2020, the future for world transport looked set to continue the steady growth seen over the past decades, with only minor and short-lived interruptions. Car ownership was steadily spreading from the OECD countries to the rest of the world and air travel was growing rapidly. The pandemic has driven home the fragility of forecasts based on past extrapolation.

Even before the 2020 watershed year, there were signs that major changes to the global transport system could occur. There was concerns about passenger and freight transport’s large and rising share of global CO₂ emissions, and about energy security in oil-importing countries (and even about oil depletion, if technical fixes such as carbon dioxide removal and/or geoengineering enabled fossil fuel use to continue unabated). If predicting transport futures is increasingly difficult, we must resort to normative planning. Given that technical solutions are unlikely to help much, a ‘low transport future’ [22] with OECD vehicular transport levels cut to 4000 p-k per capita by 2050, is proposed.

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