Autonomous vehicles will have environmental trade-offs

Optimistic predictions expect reliable autonomous vehicles to be commercially available by 2030, at a time when mobility is undergoing a shift away from traditional modes of transport and towards door-to-door services. Previous analysis suggested that public transport will lose market share to autonomous vehicles, but experts have not considered the environmental impact of changing transport use.

To address this, a recent paper by researchers from the University of Wisconsin-Madison used a stated-preference survey to reveal the potential users of autonomous vehicles and the resulting level of competition with traditional modes of transport.

The survey showed an expected increase in environmental impacts across all the categories studied, because of a shift from less carbon-intensive transport options. The researchers also confirmed that the use of electric autonomous vehicles could change this environmental outcome.

Experts expect autonomous vehicles to offer significant benefits in terms of transport operations, safety, and accessibility; however, these benefits may mask potential environmental impacts. Travel behaviour changes will accompany the adoption of autonomous vehicles. However, research to date has mostly focused on autonomous vehicle technology and not on the environmental impacts that will result from transport mode shifts. This new research, therefore, examined these impacts based on four categories: energy consumption, greenhouse gas emissions, particulates, and pollutants.

Wissam Kontar, a research assistant at the university, said: “The transportation system is on the verge of a major paradigm shift. Emerging technologies such as autonomous and electric vehicles, along with a change in commuting behaviour, will have significant operational and environmental impacts. It is of crucial importance that we consider those impacts conjointly if we are to forge efficient and sustainable mobility of the future.”

The survey conducted in Madison, Wisconsin, examined attitudes to transport modes and found that in choice experiments between private vehicles, autonomous taxis, buses, and bicycles, respondents would use autonomous vehicle taxis 31 per cent of the time because of their desirable operational and modal attributes.

Buses had a significantly longer access time because of walking and waiting, and personal vehicles were the midway choice. However, commuters who owned a personal vehicle were less likely to choose an autonomous vehicle, implying that autonomous vehicles primarily compete with public transport; therefore, policies aiming to reduce commuting in personal vehicles might not be fully successful in reducing environmental impacts.

The researchers then examined the impacts of policy and service changes via a series of simulations, which confirmed that autonomous vehicles primarily compete with the environmentally preferred transport mode, buses. They also showed that a decrease in bus travel times would cause a significant increase in bus usage.

Environmental predictions showed increases of between 5.7 per cent and 6.85 per cent in the energy and pollution categories, a significant impact, given that transport accounts for 28 per cent of the greenhouse gas emissions in the US.

To offset the environmental impacts of autonomous vehicles, the researchers considered the use of electric autonomous vehicles, considering the use phase only. The results showed that electric autonomous vehicles can offset the environmental impact of autonomous vehicles, subject to a suitable mix of electricity generation methods, and if the adoption rate of electric autonomous vehicles is over about 40 per cent.

According to the team, the new research could help researchers and policymakers to exploit the full potential of autonomous vehicles while taking any potential environmental implications into account. Cities seeking to deploy autonomous vehicles will need to steer their deployment in ways that both match consumer adoption patterns and are environmentally beneficial, they added.