Why electric robotaxis might not save the planet

What they're saying: “While electric vehicles themselves have lower emissions than traditional gasoline-powered ones, our work shows that deploying electric robocabs en masse on America’s streets could actually increase the number of trips, miles driven and overall emissions,” says Harvard law professor Ashley Nunes, the study's lead author.

What they did: By studying data from San Francisco, Nunes’ team concluded that the convenience of ubiquitous fleets of robotaxis would increase demand for rides, generating more trips and more vehicle miles traveled — erasing the electric vehicles' environmental benefits.

Key takeaway: To avoid worsening emissions, electric robotaxis would need to be 55% cleaner than today's EVs — or people need to stop riding solo, the study concluded.

• Without more renewable energy sources, as many as 75% of rides would need to be shared, up from 20% today.

Yes, but: The pandemic has soured people on ride-pooling, Nunes acknowledges, which means robocabs must reduce their carbon footprint even more.

What's needed: The researchers offered several policy recommendations, including:

• Clean up the electricity grid, using more renewable energy sources.
• Rather than subsidizing EV purchases, federal and state governments could offer discounts for ride-pooling.