My subway map is my memory album

Some people keep checklists of the countries they have visited, noting every new stamp in the passport. As for me, I keep tabs on every subway stop I take.

Like many New Yorkers, I have a tattered train map tucked in my purse. My map is peppered with black check marks, however, one next to every subway station where I've disembarked.

The paper resembles a heat map: a dense forest of checkmarks across Manhattan, a smattering in Brooklyn, and just a few in the other outer boroughs of Queens and the Bronx, where the map is still mostly bare.

I've made most of the checks during the course of daily life in this city; jobs in Midtown, jobs near Wall Street; shopping expeditions, dinners out.

I offer to meet my friends by their offices or apartments, if only for the pleasure of exploring the neighborhood between the subway stop and the final location.

I've lived in New York for more than a decade, long enough so that I miss the jingle of subway tokens in my pocket - it's all done with magnetic-striped MetroCards now.

I have certain rules to earn a checkmark, not unlike a child earning a gold star in class. I have to get off the train at the actual stop - if I'm merely passing through, it's not the same. And in order for the stop to count, I need to walk at least five blocks in one direction away from the train stop to get a feel for the neighborhood.

If I don't like the area, after five blocks I turn back and get on the next train home. But more often than not, I will keep walking.

Looking at the subway map brings back memories for me, just like a photo album.

The Coney Island stop on the D train reminds me of the trip I took with friends to wolf down coal-oven pizza at Totonno's, followed by more eating in the Russian shops and restaurants along Brighton Beach.

The Union Square train stop on the yellow line is all about the green market set up there four days a week.

I think about emerging from the darkness of the underground train on a summer afternoon, squinting at the sunshine, and inhaling the spicy fragrance of fresh basil sold at a nearby farmer's stand.

Every train stop is a memory or a potential adventure.

I've taken subways in other cities and countries, too. In Moscow, the subway stops have elaborate mosaics and chandeliers. In Tokyo, "people-pushers" are employed to ensure that train doors close on cars filled to maximum capacity.

I've ridden the Tube in London, the Paris Métro. Every subway looks a little bit different and a little bit alike. Every train is full of people trying to avoid eye contact with their fellow passengers, studying newspapers, their shoes, and. of course, the subway map.

I can't help studying the subway maps in these places, too, wondering what lies above ground as the train stops or speeds by. Is this a residential or business neighborhood? Is it affluent or poor? Is this an ethnic neighborhood? Is there a park or a playground just steps away?

Somehow, road maps don't have the same effect on me. For some reason, a road map is just about getting in the car and figuring out how to get from point A to B.

Maybe it has something to do with the seeming infiniteness of a road map: When I look at one, I see a labyrinth of snaking streets and highways. I can take any one of them, turn at virtually any point, and keep going in a new direction.

The potential destinations are endless on a road map. Somehow, the subway map seems more finite, more intimate.

Don't take this to mean that I am starry-eyed about the New York subway system.

Like any other straphanger, I recoil at the sight of rats scurrying across the train tracks. I loathe the rush-hour crush of bodies on the Lexington Avenue line, where a stranger inevitably sneezes on my head.

I am regularly exasperated by train delays, the gantlet of panhandlers, and malfunctioning subway turnstiles that leave me swiping my MetroCard in vain, windmill-like, as the train whizzes past me.

But I think of J. Alfred Prufrock, the eponymous narrator of the T.S. Eliot poem, who says, "I have measured out my life with coffee spoons."

We all measure out our lives in some way - some by the numbers on the bathroom scale, others by the number of zeros on the bank-account statement.

If I am, in effect, measuring out my daily travels and travails with subway stops, I find some satisfaction in that.

Like many people, I can't say with any certainty that I know where I am going in my life. But when I look at my creased and marked-up subway map, I surely know where I have been.