This weird Twitter thread began Friday in which Tesla CEO and unrepentant over-tweeter Elon Musk started arguing about whether trains or cars belong in tunnels.

BART picked a fight with Musk after seeing him tweeting about the virtues of tunnels, and asserting, oddly, that trains don't belong in them, they belong above ground.

Possibly using part of a campaign to boost ridership, BART responded by tweeted a diagram showing how twice as many people per hour can cross the Bay on its trains as can travel over the Bay Bridge in cars. Musk took these as fighting words, because of his beloved Boring Company project which proposes that we can solve all our traffic problems by putting superhighways underground.

Shockingly, Musk didn't really engage with BART after they started responding.

In other news, Elon Musk spends too much time on Twitter, and his tweets have caused Tesla's stock to sink multiple times.