Self-driving cars are speculated to worsen air pollution, noise pollution, and sedentary lifestyles, to increase productivity and housing affordability, reclaim land used for parking, cause greater energy use, traffic congestion and sprawl.

Automated vehicles could reduce energy consumption in transportation by as much as 90%, or increase it by more than 200%, according to research from the Department of Energy (DOE). That difference matters—more than a quarter of greenhouse gas emissions come from the transportation sector, according to the Environmental Protection Agency (EPA).

If every vehicle on the road is autonomous, their control system can reduce fuel consumption by 18 percent and carbon dioxide emissions by 25 percent, while boosting travel speeds by 20 percent. “A single intervention having 20 to 25 percent reduction in fuel or emissions is really incredible.

The cars were found to be responsible for contributing up to 20% more greenhouse gas emissions compared to human-driven vehicles, due to the excessive energy usage needed not only to power the onboard systems but the car itself under all the extra bulk, according to the study.