Commitments : Missing: One Identity Left Behind in Previous Car : Aging: We define ourselves through what we drive. But how can our wheels tell us who we are when every year brings 300 new models, each one promising a sleeker, safer you?

A woman I work with, who’s about my age, is in the market for a new car. The last time she bought a car was 10 years ago. At the time, her children were small, so she went shopping for a safe, sturdy, celibate four-door . . . and had a mid-life crisis inside the dealership, which caused her to drive off in a spiffy convertible.

I asked her why.

“Because,” she said, shaking her shoulders like Charo doing cuchi-cuchi, “you know.”

After 10 years, the “you know” has been exorcised. “I just wouldn’t feel comfortable buying a sports car again,” she said. “And this is because, I’m, uh . . . “

An old bag? I volunteered.

“Yes, an old bag,” she said. “So what does an old bag buy?”

A 1973 Nova always worked for me.

Let me caution you right away: This is not a man-woman thing. This is not about how women buy cars as opposed to men. This is not about how women are old bags. I am an old bag too.

This is a middle-age thing.

This is about finding your identity through what you drive.

Twenty years ago, you bought cramped cars with low fuel-consumption to do your part to help protect the environment. Ten years ago, you bought bulky cars with childproof door locks so you could protect your kids. Now your kids are driving their own cars, and you couldn’t care less what gas costs as long as you don’t have to wait in line for it. This next car is for you--if only you knew who you were.

I am past the convertible stage now. A couple of years ago, I coveted a Mazda Miata. I went to test-drive it, and it felt as if I were sitting in a shoe box; I thought about my chances of surviving an accident, and not even with another car--if my Miata got hit by a large dog, they’d have to scrape me off the road with a spatula. Then, when my test drive ended, I couldn’t get out of the car. My center of gravity was too low. I had no push-off. I had to sort of roll out onto one knee. If you’re going to buy a car, at least you ought to be able to get out of it without risking arthroscopic surgery.

The same is true of Jeeps and small trucks, which everybody seems to want now, as if paved roads were going out of style. Am I missing something here? Are we preparing to occupy Switzerland and this is the way we’re crossing the Alps? Riding in a Jeep is like riding in a tin can. Half the time, you feel as if you’re in a Cuisinart and somebody hit the “pulse” button.

And you’re sitting so high you can get vertigo. A friend of mine shelled out $27,000 for a Chevy Blazer and asked for the step-ladder option so he could drive it home. I’ll bet the highest incidence of broken legs among middle-aged men is caused by dismounting from a Ford Explorer.

Getting back to my friend: She stares at cars all the time now, trying to figure out which one is her. She goes to the supermarket, but doesn’t actually buy food--which hasn’t endeared her at home--because she spends all her time walking through the parking lot casing cars.

Recently, she was out jogging and spotted a car she liked stopped at a light. She yelled out to the driver, “What’ve you got under the hood?” The terrified man--obviously thinking that a woman in jogging shorts who approached him in his car to ask him what he had under the hood must be a prostitute--quickly shut his window and sped away.

“It was an Altima,” she remembered. “Who makes Altima?”

Who makes Altima? Who makes Avalon? Millenia? Infiniti? Cirrus? Aurora? They all look like fat Faberge eggs. Are they Japanese? Are they American? (Hint: They’re not European. European cars don’t have names, just letters and numbers. 850, J30, C-280, E-400, 325i. Anybody out there got bingo?)

Remember when it was simpler, when cars had rules? You were a Ford man or a GM man. If you were a GM man, you started with a Chevy, you bought an Olds when you got married, and if you got a promotion--whoa, here comes Mr. Buick! You moved up within the known order. The kind of car you owned reflected your spot in the food chain.

Now it’s so confusing. Nobody’s a Ford man anymore, nobody sticks with a company his whole life; if Henry Ford were alive today, he’d probably drive a Lexus! Madison Avenue has made us a nation of car-buying Sybils. How can your car tell you who you are when every year 300 new cars come out, each one promising a sleeker, safer, more roomy you? Whatever happened to Plymouth Furys, which didn’t promise you anything but a radio and a heater?

I feel sorry for my friend, trying to discover which car is her.

You can’t find yourself in the rearview mirror anymore.