The A train took a good 15 minutes — maybe 20 — to arrive. And when the doors opened, I swear I stepped off the platform into 1974. The car was filthy. A crumpled McDonald’s bag was on the seat beside me. Loose newspaper pages were blowing around on the floor. I didn’t notice any ’70s-era graffiti. But you could barely see out the windows, they were so scraped up with 2008 scratchiti.

And the service! A bridge was out on the way to the Rockaways. So half the people in my car — including three moms with strollers and cranky kids — were doubling back at Rockaway Boulevard for a subway-bus-subway shuttle reverse.

“And now they want to raise the fare to $3?” one of the moms grumbled over her shrieking child.

I just shrugged.

You can’t prove a social trend from a single subway ride. And I did get home eventually.

But lately, I keep noticing signs of a New York slip-back — little reminders of the last time the world’s greatest city really was in undeniable decline.

Have you noticed it too?

More homeless people on the sidewalk and in the subway. Garbage sitting longer in the street. A few more boarded-up buildings in iffy neighborhoods while the owners struggle with their bankers or try to decide if the renovation numbers still make sense.
I don’t drive. So I can’t speak first-hand about squeegee men. But I hear talk.

Then I read that the city is skipping a recruit class at the Police Academy. And I hear about the giant budget deficits that loom in Albany and at City Hall.

Don’t you have to wonder?

Are we returning to shabbier times in the city? Are the various troubling signs coalescing into a genuine trend? Are we about to make the mistakes we swore we’d never make again?

The last time we were here, in the 1970s, the politicians did as politicians do: They tried to cut the things that no one would notice, not at first, anyway. Subway maintenance. Police, fire and sanitation headcounts. Teacher training. Building inspectors.

A few quiet years of this, and the city was hollow at its core.

As I rode the A train home the other night, I was remembering another train ride. I’m guessing 1990. The worst of the bad days were behind us. The city had inched back.

This time, I was on the No. 1 train, heading to the Bronx with David Gunn. He was president of the Transit Authority. He deserves a major part of the credit for pulling the subway back from its last abyss. As we rode and talked about New York’s hard road back, Gunn reached down and grabbed a candy wrapper from the subway car’s floor.

He was the president of the Transit Authority and he was picking up trash.

“It’s the little things,” Gunn said when I asked him why he did that, the wrapper still in his hand. “Before you know it, those little things turn into big things. And then the whole thing comes crashing down.”