It started innocently enough. Arlington reader Barry Coyne suggested that motorists could ward off collisions with animals if they would simply get an inexpensive "animal repeller" that fits on front bumpers. This small device is said to emit a wind-activated ultrasonic sound, beyond the range of human hearing, that warns most animals of the approach of oncoming vehicles.

This is no small problem. From collisions each year with deer alone, scores of people are killed, hundreds are injured and damage to vehicles amounts to millions of dollars. An estimated 200,000 deer annually are killed by vehicles. Because this is the mating season and deer are more active, many area residents are reporting collisions and near-collisions with the animals.

Dr. Gridlock called Barry Coyne and asked where to get one of these warning devices, and was referred to Carol Wright gifts of Lincoln, Neb. For about $4, the doctor ordered one for a drawing, published Coyne's suggestion, and noted that the American Automobile Association sells a similar device, called SAV-A-LIFE, for about $20. Readers were invited to comment.

Well, the doctor was bombarded with responses. Many readers said these devices work wonders, but just as many wrote in to say the "deer whistles," as they are sometimes known, are useless.

"Last month we went to the National Zoo and blew one of these whistles at the animals," said Guy R. Hodge, information director for The Humane Society of the United States. "Then we blew on a banana. We could not detect any difference in reactions in the animals." Hodge concluded after a review of manufacturers' claims that there is no evidence the whistles emit an ultrasonic sound, or that animals are necessarily repelled by ultrasonic sound.

Readers passed along plenty of critical comment. "As deer populations explode around the country, it's disheartening to learn that deer whistles don't work," editor Duncan Barnes wrote in this month's issue of Field and Stream magazine.

In some of the most-quoted literature, researchers at the Utah Division of Wildlife Resources tested SAV-A-LIFE and Game Saver deer warning whistles on 150 groups of deer. A summary of their study concluded that the whistles don't work: "Deer don't react any differently to a vehicle equipped with the warning whistle. A deer in the road continues to cross the road. Deer that are feeding continue to feed. A running deer keeps running. A standing deer stands."

"The deer whistle has everything right for a scam; you can't hear the whistle," Patrick Bedard wrote in Car and Driver magazine. Bedard said he had noticed no impact on dogs in or near the road.

Carol Vitello, a sales representative for SAV-A-LIFE, says the product "is 80 percent effective in cutting down the chances of hitting an animal. Unfortunately, there are a lot of cheap imitations on the market that don't emit ultrasonic sound."

Rob Krebs, the area spokesman for the AAA, said he was unaware of any controversy over the devices. "We have motorists who swear by them. Because they do and because they may save you from getting into a wreck, we think it's worthwhile to at least make them available."

Vitello, asked for data supporting the efficiency of these devices, referred to testing done in Finland and Austria.

Hodge, the Humane Society specialist, reviewed that work and concluded that "the test findings were not scientifically valid."

Vitello counters that the Humane Society of Bend, Ore., uses her company's product. ("Our chapters are independent and autonomous," Hodge said.) The California Highway Patrol, 23 state police departments, and several large companies such as DuPont and Amoco also use the devices, Vitello said. She said she would send more scientific testing results, and testimonials. Those who want to know more might contact her at 212-826-6611.

Locally, about 500 Montgomery County police cruisers have the SAV-A-LIFE product (at a fleet price of $7.50 each). "I asked a couple of guys if they work and they said, 'Well, we haven't hit a deer yet,' so maybe there's some truth to it," said Sgt. Harry Geehreng, a police spokesman. Geehreng said he could not recall any deer being hit before the devices were used, either.

"It works on a straight-away road," said SAV-A-LIFE's Vitello. "The sound travels straight out. The animal has to be on the road or on the side of the road to hear it. The device should be cleaned, about every time there is an oil change."

Dr. Gridlock, lacking the scientific credentials to analyze the wealth of conflicting information, and limited by space, will now get out of this thing by noting that we have at least moved a step forward from reader Coyne's original well-meaning intention: These devices, if nothing else, are controversial.

Some letters:

Please, no! Not deer whistles!

I submit that any company claiming to have effective deer whistles should also provide complete scientific test results from an independent testing laboratory, substantiating the claim that the devices actually reduce the incidence of collisions.

Deer whistles are as effective as whistling in the wind. Don't waste your money. DOUG INKLEY Germantown

The animal repeller device is terrific. I drive between Emmitsburg {Md.} and Gettysburg {Pa.} at least twice a week. My route goes through the Gettysburg National Park, which has a large deer herd. It's been nearly a year since I installed this device and to date I have had no problems with deer. I heartily recommend the device for anyone driving in rural areas; it makes the road safer for motorists as well as animals. SUSANN SAMPLES Emmitsburg

Back in Texas we call your ultrasonic deer whistles "elephant whistles." Why? Well, even with the whistles you still see -- and hit -- lots of deer, but no one has ever hit (or seen) an elephant.

Seriously, the whistle works to frighten deer, but many times they jump instinctively and still run into traffic. The answer remains DRIVER VIGILANCE. DAVID A. RUBENSTEIN Springfield

My husband and I were driving on Interstate 64 west of Richmond when a deer came out of the woods and plunged down the bank toward the road just ahead of us. When it reached the bottom of the ditch, it turned around and raced back up the bank and disappeared into the woods. I've lived in the country all my life and I have NEVER seen a deer turn around so rapidly.

My husband's car is equipped with the animal warning whistles on either side of the front bumper. Ours were purchased from The Plow and Hearth in Orange, Va., for $15 to $20. Of course, I can't prove that the whistles were responsible for the deer's turnaround, but the last deer that came that close to that car caused extensive body work to the front of the car.

Hope this helps. ABIGAIL N. JAMES Orange

I can tell you from experience that ultrasonic alarms don't make a bit of difference. I encounter deer frequently in my daily commute from Frederick to upper Montgomery County. They didn't react any differently to my approach when I used the alarms.

To date I have seen no scientific evidence that these devices do anything but generate profits for mail-order houses. I hope someday that an effective alert mechanism is developed. Until that happens, your readers would be best advised to refrain from purchasing this latest example of snake oil. JOHN KEARNEY Frederick County, Md.

Four years ago, I started commuting to Washington from Bedford County, Pa., a rural area. During my first month I hit three deer. After installing the animal repeller, I did not hit another deer for the next 11 months driving this route. In fact, I have had no close encounters since.

Was it the ultrasonic sounds from the animal repeller that halted the deer, or was it just a change of luck? WILDA V. MALLOW Washington

Well now, that is the question, isn't it?

Dr. Gridlock appears in Metro 2 each Friday to explore what makes it difficult to get around on roads, from misleading signs to parking problems to chronic bottlenecks. You can suggest topics by writing (please don't phone) to DR. GRIDLOCK, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Please include your full name, address and day and evening phone numbers.