DEAR ABBY: Although I have read your column for many years, I am not sure that this topic has ever been addressed.

Why are people so careless when opening their car doors? I don't know how many times I've witnessed people carelessly opening their car door, only to let it slam into the car next to them. Not only do they leave very noticeable dents on other people's cars, I'm sure they can be damaging their own car doors.

I have taught my two small children never to let the door hit the car next to ours. I'm hopeful this message will make people stop and think the next time they open their car doors.

Thanks for letting me get this off my chest. You may use my name. -- LYNDA GOVEDNIK, MINOOKA, ILL.

DEAR LYNDA: People who open the doors to their vehicles, allowing them to strike the cars parked next to them, are thoughtless and inconsiderate. And they rarely expect to be caught. I put them in the same class as shoppers who allow their grocery carts to scrape or "ding" cars in the parking lot. The only consolation is the knowledge that, in most cases, what goes around comes around. But it's small consolation, and never soon enough.

DEAR ABBY: The letters you printed from people sharing memories of President Harry Truman delighted me. May I add my own:

I was 10 years old. It was summer, and I was visiting my aunt and uncle, who happened to live just a mile west of the Truman Library in Independence, Mo. One afternoon they took me for a tour. To top it off, we walked around to the northwest side of the building where the former president's office was.

To our amazement, there he stood with his chauffeur, getting ready to leave in the biggest, shiniest black car I had ever seen. Instead of leaving, he greeted me, told his driver to unlock his office, and invited us inside for a visit! My only regret is that none of us had a camera.

Mr. Truman sat me down with him at his huge desk and told me I reminded him of his daughter, Margaret, because of my long blond hair and blue eyes. I was spellbound, to say the least. Then I noticed his big, black piano, and he asked me if I could play. I told him yes, and he insisted that I play something for him. I told him my favorite piece was the U.S. Marine Corps Hymn because my brother had joined and I had practiced long and hard on it. Mr. Truman said, "Play away!" Believe it or not, I made it through the whole hymn without missing a chord.

Today my husband and I live only 16 miles from Truman's birthplace, Lamar, Mo. I have visited it often and have shown it to every out-of-town visitor we've had.

I will always treasure the memory of one of America's most important men, a U.S. president who made time for an awestruck 10-year-old from southeast Kansas. -- JEANNE ECCHER, LAMAR, MO.

DEAR JEANNE: Thank you for sharing your heartwarming encounter with Harry Truman. And you didn't have to pony up a dime for it. My, how times have changed!

For Abby's favorite family recipes, send a long, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Cookbooklet No. 1, P.O. Box 447, Mount Morris, Ill. 61054-0447. (Postage is included.)

DEAR ABBY: The letter from "Someone in Georgia," the mother of a child who had died from an overdose of drugs, prompts this letter. She asked why no one had warned her about her child's drug problem while he/she could be saved. Perhaps this is the reason why:

The mothers in our community have often discussed the necessity for openness and sharing information about each other's kids. Sadly, this commitment came crashing down on my family.

My son (I'll call him "Mike") spoke to school counselors about his friend "John's" drug experimentation, which he had both heard about and witnessed. Mike wasn't the first to reveal it to school staff. But he was the only one who agreed to tell John's parents about it while in a protected school setting, in the presence of professional counseling staff. Mike was sure that John's parents would believe him and appreciate his honesty if they heard it straight from him. My husband and I naively agreed.

The response was devastating. John's parents called Mike a "traitor," a "narc," and many names that are unprintable. John has predictably denied everything. His parents cried "conspiracy, competition, vindictiveness," and continue to claim that Mike had ulterior motives. They blamed the accuser and became aggressors instead of listeners, criticizing and questioning the motives of my entire family. Is making Mike the enemy and a scapegoat a twisted way to deflect attention away from their own son?

I now regret that I didn't tell Mike, "You don't tell on friends." But the knowledge had burdened him for months. I assumed that personal integrity, mutual respect and honest evaluation would prevail. But John's parents have remained in vehement denial, fueled by their child's accomplished lying.

The school principal tells me that it can take from 20 to 30 incidents -- even up to 60 -- for some parents to look objectively at a child's drug problem, and that the substance abuse is most likely still continuing or will return.

This has been awful. Our household is still reeling. We thought of John's parents as friends, fair people. Mike still feels threatened, and even I feel threatened.

Now I ask myself, if the situation had been reversed, would my husband and I have been any more objective? Parents want to believe their children; we need to believe them. Nobody wants to face the darker possibilities. No parent wants to think that perhaps their parenting skills or their family's communication system has failed.

"Someone in Georgia" stated that she would have listened. Ideally that would have been true. But when someone tried to reach her, perhaps she was steadfastly believing something else. -- SADDER AND WISER NOW

DEAR SADDER AND WISER: Your theory that the reaction of John's parents was an attempt to divert attention from their son by focusing their anger on yours is perceptive. Their protective instincts prevented them from keeping an open mind, and they went on the attack. It is possible that they would have been less hostile and defensive if you and your son had approached them privately, instead of involving school authorities in the intervention.

Please don't second-guess your own judgment. Your son did the right thing by speaking out. It showed courage and a sense of responsibility. No one does a friend a favor by remaining silent when friends engage in self-destructive and possibly life-threatening behavior.

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DEAR ABBY: I am a 14-year-old girl and I'm very worried. My mother is having a baby this summer. I'm happy for her and my stepfather (this is their first baby together), but I think they are expecting me to take on a lot more responsibility than I had anticipated.

My mother and my aunts make comments like, "Get used to changing diapers now, and you'll be a natural once your new brother is born." Or, "Just think, you have a baby sitter in the house so you won't have to worry about getting one."

Well, I don't want to be a mother to this baby. I just want to be a sister, one who loves and holds, and occasionally changes diapers or feeds the baby.

I don't know how to talk to my mother about this. I am afraid that I will upset her and she'll think I don't want this newcomer in our family. She has included me in a lot of the preparations, like shopping and decorating the baby's room.

My mother works full time and my stepfather works six days a week. I already take care of my younger sister after school and when my parents go out occasionally.

I want to enjoy my teen years, free to make my own plans that won't be overruled when my parents want me to baby-sit. Can you give me any suggestions? -- THE OLDEST SISTER

DEAR OLDEST SISTER: It is not unreasonable for your parents to expect you to watch the baby for short periods when they are absent, but they should not depend upon you for all of the baby's care. You will be in school for a good part of the time while your mother works, so she will need another caretaker for your brother in any event.

Show this letter to your parents. The important thing to remember is "compromise": They should not expect you to be an unpaid baby sitter for your new brother; you should expect to pitch in some of the time. You might discover, after the baby arrives, that you want to spend more time with him. Good luck, and congratulations on the new arrival.

DEAR ABBY: I got the shock of my life last week. I live in a well-lighted, expensive neighborhood, in an electric-gated, fenced home.

I was upstairs in my bedroom when suddenly there was a knock on my bedroom door and in walked my two grown sons.

The youngest had climbed over the gated fence, gone into the gated backyard, put a credit card into the breakfast room door, found my purse and got my keys so that he could turn off the alarm in my car, get the remote control and open the gate, so that they could get in, come up the stairs, knock on my door and walk in. I nearly had a heart attack.

Abby, anyone could have done that, and I might not be sitting here writing to you. Everyone, please: Beware and be careful. -- J.P.C. IN L.A.

DEAR J.P.C.: Since you now feel vulnerable in your home, it's time to contact a security company and have someone there evaluate your premises. For openers, you need to purchase a deadbolt lock for the breakfast room. And for your peace of mind, instruct your two budding second-story men to never again enter your home without calling first.

For everything you need to know about wedding planning, order "How to Have a Lovely Wedding." Send a business-sized, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Wedding Booklet, P.O. Box 447, Mount Morris, Ill. 61054-0447. (Postage is included.)