As I wait at the mobbed Atlantic Avenue subway station after a Nets basketball game a week ago, the No. 3 train finally arrives and we all pile in. The train moves along, but after 15 minutes comes the terse announcement: "The next and last stop will be Wall Street."

We swarm out at Wall Street and wait for the next train, which the electronic message board says will be there in eight minutes. It arrives and dumps its passengers as well. Last stop. OK, now the board says a No. 2 train will show up in 10 minutes.

Guess what?

Couldn't that message board have informed us that trains were out of service uptown between Chambers Street and Times Square due to a major water main break that happened earlier that evening?

After we wait in vain for more than half an hour, two guys in MTA uniforms appear. One tells us that service uptown on the Nos. 1, 2 and 3 trains will be "running, but very slow." The other says it is totally down and suggests we walk over to a Lexington line train. Hmm . . .

Other weary riders and I climb out of Wall Street station and into the damp darkness. As we trudge two blocks east to the Nos. 4, 5 and 6 lines, I trip over a badly cracked sidewalk and crash to the pavement. Another member of our ragged subway army helps me up. OK, no broken bones.

I take the No. 4 train to 86th Street and Lexington Avenue, wait for the crosstown bus, and arrive home more than 21/2 hours after the game ended, with a bruised arm and torn pants.

The city's infrastructure has been crumbling for decades. The outdated subway signals, our ancient bridges and cracked streets cause agita for all of us. Mayor Bill de Blasio joined 60 other mayors nationwide Thursday to plead the case for more federal mass transit aid, saying the nation has been going backward in terms of investing in transportation infrastructure.

Hopefully, someday Congress will offer the help we need, before a disaster strikes.

But in the meantime, couldn't the MTA have let us know about a water main break that happened hours earlier, and used its prized electronic message boards to clearly explain the situation to riders, instead of letting us roam downtown NYC in the dark?