Want to spend a day riding the whole Metrorail system? This challenge is for you. (WMATA/WMATA)

His latest attempt took seven hours, 27 minutes and 49 seconds.

“The first question most people ask is ‘Why?’” Baker wrote in a blog post detailing the ad­ven­ture. “Half of it is my love of mass transit ... The other half? Simply because it’s there.”

Now Baker is challenging other mass transit enthusiasts to try to beat his time; he’s calling it the DC Metro Challenge,and apparently he’s already attracted his first challenger.

Baker isn’t the first person to attempt the journey. In 2001, Alan J. Sussman completed the ride, boarding at Glenmont at 8:39 a.m. and emerging from the same station at 4:27 p.m., according to a Washington Post article published in January of that year.

“I can’t believe anyone else would be so crazy,” Sussman said at the time.

Turns out, someone is. Sussman now occupies the No. 2 spot (out of two people) on Baker’s leader board.