In the coming decades, autonomous vehicles (AVs) will likely cause unprecedented disruption to the passenger vehicle market. Under optimistic projections, AVs are anticipated to reach a 50 percent market share by 2040 and 90 percent share by 2050, essentially replacing all human-operated vehicles by the second half of the century.

While the promised benefits of AVs – safe, convenient, and accessible transportation – are driving these bullish forecasts, for those pursuing a clean transportation future, the critical question is: how will AVs impact greenhouse gas emissions?

The answer depends upon the choices society makes in deploying this disruptive technology. A 2013 study by the National Renewable Energy Lab (NREL) found that AVs could reduce personal vehicle energy use by up to 90 percent or increase energy use by 250 percent, depending upon ownership model and power source assumptions. Similarly, an October 2016 McKinsey and Bloomberg report modeled transportation sector energy use in three AV deployment scenarios, resulting in a wide range of emission impacts.

These studies indicate that AVs have the potential to deliver significant progress in all three of the emission-reduction pathways for the transportation sector: switching fuels to lower carbon sources; reducing vehicle miles traveled (VMT); and improving vehicle efficiency. However, if deployed with little regulation or intention to reduce emissions, AVs could deepen our societal dependency on gas-powered personal vehicles and increase our commute times and distances.

Fuel-Switching to EVs

The greatest determinant of AV’s emission impact will be the extent to which the new technology facilitates fuel switching from gas-powered internal combustion engines (ICE) to electricity-powered vehicles (EVs). A May 2017 study by University of California, Davis (UC Davis) and the Institute for Transportation and Development Policy found that complete electrification of automated vehicles globally would reduce urban transportation emissions by 60 percent compared to a business-as-usual (BAU) scenario.

Many experts are confident that the AV and EV markets will inevitably develop together, and leading carmakers are investing heavily in both technologies. However, bolstering these economic trends with effective policies linking these two technologies will ensure that AVs accelerate the transition away from gasoline-powered vehicles in both urban and rural areas.

Significant investment and strategy for creating the charging infrastructure and capacity is also needed if AVs are to be deployed as EVs. Further, utility business models for charging remain uncertain. These challenges will need to be addressed for the AV/EV market to develop rapidly in the coming years.

Reducing Miles Traveled

Beyond their fuel-switching potential, AVs could also reduce VMT if they are deployed primarily as shared vehicles. Enthusiasts envision urban areas patrolled by electric AV fleets delivering on-demand rides and sparking a virtuous cycle: shared AVs reduce car ownership, which enables repurposing of parking and road space for bike lanes, green spaces, and housing. This in turn, proponents argue, will accelerate urban densification, increase alternative transportation use, and further reduce car ownership. The previously noted UC Davis study concludes that a shared AV future would decrease 2050 urban transportation emissions 25 percent compared to BAU.

However, a shared AV network must be supported by a multi-dimensional policy and urban planning approach that encourages ride-sharing. These policies include roadway tolling, increased parking fees, densification incentives, ride-sharing incentives, and biking or walking transit corridors.

Without a suite of policies and plans, the comfortable, safe, and productive transportation provided by AVs will enable urban sprawl, increase personal car ownership and VMT, and exacerbate roadway congestion.

Increasing Vehicle Efficiency

Finally, AVS offer a variety of vehicle efficiency improvements. According to the NREL study, platooning—grouping several AVs together in a series could contribute a 10 percent improvement in vehicle efficiency due to decreased drag.  Additional  efficient driving patterns that smooth acceleration and deceleration can also reduce energy intensity by 20-30 percent. The study also found that AV safety improvements could enable lighter, more efficient vehicles, reducing energy intensity up to 45 percent. However, most of these efficiency benefits require a high penetration of AVs, so will take time to accrue.

Maximizing AV Benefits

Autonomous vehicles are a powerful technology that can be used as a tool to accelerate fuel switching, minimize vehicle miles travelled, and improve vehicle efficiency. Whether AVs reduce our emissions by up to 85 percent or increase energy use and personal vehicle dependency depends upon our will as citizens and as a society to maximize the benefits of this tool.

At Clean Energy Transition, we will be working with policy makers and thought leaders at the city, state, and federal levels to build support for a climate-positive AV future.

Jamie Daudon served as an intern for Clean Energy Transition from January - June 2017. He graduated Colorado College with a major in Philosophy, Politics, and Economics and a minor in Physics in 2016.