It won’t cause any full-on rush-hour meltdowns, but from mid to late August, Muni will again annoyingly close the subway tunnels from 9:30 p.m. to 1 a.m., and replace that service with shuttle buses.

It’s something of a breakthrough that the SF Muni bus decks at the finally reopened Salesforce Transit Center will resume service this Sunday, August 11. But longtime Muni riders know that with this particular transit organization, it’s often one stop forward and two stops back. And that’s the case again here, as Curbed reports that Muni will be shutting down its subway tunnels at nighttime for much of the month of August. Such closures have occurred for months at a time in recent years for track and tunnel work, and according to the official announcement from Muni, “The subway will close between Embarcadero and West Portal stations nightly at 9:30 p.m. starting August 12 and continuing for approximately two weeks.”    

These closures will affect the the J-Church, K-Ingleside, L-Taraval, M-Ocean View, N-Judah, and T-Third lines, though again, not until 9:30 at night. Each of these tunnel routes will be replaced by shuttle buses. These routes will go into their regular Owl service at 1 a.m., and the tunnels will reopen for trains on their usual schedule — theoretically at 5 a.m., but of course this is Muni, so you never know.

To that end, Muni is setting the expectation of slower service during that 9:30 p.m.-1 a.m. window. “Muni customers are encouraged to leave extra travel time when riding Muni during subway closure,” they say in their release.

Curbed digs deep in those travel time numbers, and finds the on-time performance of those six light-rail lines has not been great lately. (You may have already noticed this.) The SFMTA does publish on-time performance data online, and Curbed found that for the month of June, the trains that use those tunnels were on time only 46% of the time.

Muni argues this closure will ultimately improve that performance. They say in their Subway Maintenance Project announcement that the closures “will give us an opportunity to do complex work aimed at making subway operations more reliable and preventing future breakdowns.” Muni also adds that they’re planning to do a similar shutdown of these tunnels in December, though they don’t yet know specific dates for those closures.

Related: Muni Dumps Water On BART, Shuts Down Embarcadero Station [SFist]

Image: Torbakhopper via Flickr