BART is 43 in human years, but in public transportation years, it's like a zillion and showing its age. As such, the agency has budgeted $20 million this year, and then $30 million every year going forward, for track upgrades and maintenance. And now, as we warned in June, some "urgent track maintenance" is going to close the Transbay Tube this weekend. Yes, even on Monday.

Writes the SFMTA, cheerily:

This holiday weekend is shaping up to be sunny, warm — and under construction. We’re working through Labor Day Weekend to make transit better for everyone. With impacts to Muni, BART and traffic, this is a chance to take advantage of the final days of summer and walk, bike or take the bus where you need to go.

So what's a traveler to do? AC Transit, Muni, Golden Gate Transit, and SamTrans will try to fill in the gap, running shuttle service across the Bay Bridge with a bus leaving about every minute-and-a-half. This shuttle service was indeed very frequent, and underused, during the first weekend closure last month.

Also, while you're in the process of planning your weekend, don't forget about the Billy Joel concert going on at AT&T Park on Saturday. That's from 8:00 p.m. to 11:00 p.m. and an attendance of 50,000 is expected.

Last, some changes due to Central Subway construction to note, (especially if you're planning to the piano man thing).

Track work for the Central Subway project will take place at King and 4th streets beginning this Friday at 10 p.m. and running until 5 a.m. Tuesday. During construction, there will be no T Third service between Embarcadero Station and 4th and King streets. N Judah service will be single tracked through the construction zone. There will be no E Embarcadero service, and F Market service will be provided by buses.

"[W]e’re not resting on our laurels," BART’s assistant general manager for operations tells the Chronicle. The pressure is on. We’re working to make this as painless as possible.”

Previously: BART Shutting Down All East Bay-SF Service During Two Late-Summer Weekends