If you live in the Bay Area, there’s one question you’ve probably asked at some point: why on earth doesn’t BART run past midnight?

Over Presidents Day Weekend, it did. When construction shut down parts of the Bay Bridge, BART ran around the clock between San Francisco and the East Bay. We head underground to find out what happens when the trains don’t stop — and why it can’t be like this all the time.

Produced by Rachel Waldholz. Camera by Julia Marshall, Amina Waheed and Byron Wilkes. Maintenance footage courtesy of BART.