John O. Nestor, 86, a physician who was recognized for vigilance in screening new drugs while at the Food and Drug Administration--and also for his practice of resolutely adhering to the speed limit while driving his car in the fast lane--died of renal failure May 1 at the Hospice of Northern Virginia.

Dr. Nestor's celebrity as a motorist can be traced to a letter he wrote to The Washington Post in 1984, explaining his conduct on multilane highways. The letter led to the coining of the term "Nestoring" to describe actions such as his, of firm conformity to standards and regulations that are more honored in the breach.

In the letter, he said that on divided highways, he drove in the left lane with cruise control set at the speed limit because that was usually the smoothest lane. He said he avoided slower traffic moving in and out from the right and avoided resetting his cruise control with every lane change.

"Why," he asked "should I inconvenience myself for someone who wants to speed?"

Responses, often couched in vehement terms, were swift, and the argument has been resurrected periodically down to the present day.

An editorial that appeared in The Post in February said that Dr. Nestor, a veteran of nearly 70 years of motoring, was "still Nestoring," although not on four-lane highways as often as he had in the past.

As an FDA medical officer, Dr. Nestor was, among other things, a colleague and supporter of Frances Kelsey in the 1960s when she was reviewing the drug thalidomide in what has become a key episode in the history of drug safety.

Thalidomide ultimately was blamed for birth defects elsewhere in the world of thousands of children who were born without limbs. Kelsey was credited with preventing the drug's use in this country, and according to an article in The Post by reporter Morton Mintz, Dr. Nestor "had reinforced her skepticism" about the drug.

Dr. Nestor, a pediatric cardiologist who lived in Arlington for more than 50 years, was born in Franklin, N.J., graduated from Georgetown University medical school and won a Bronze Star for valor while serving as an Air Air Forces flight surgeon during World War II.

While a bombing and strafing raid was underway in 1944 on the base in Corsica at which he was stationed, he left the safety of a trench to administer first aid to the wounded and to see to their immediate evacuation.

After serving as chief resident at Children's Hospital, he went into private practice. He also was a consultant to hospitals and government agencies, taught pediatrics at Georgetown and Howard University medical schools and published numerous articles. He joined the FDA in 1961.

February's Post editorial said that Dr. Nestor's FDA career appeared to suffer for a time in the 1970s, "apparently because he resisted speeding up approval of certain drugs that he felt hadn't been adequately tested." But, the editorial said, the agency eventually corrected itself, and he received a public apology.

After recalling Dr. Nestor's faithfulness to his principles, the editorial again considered his driving habits and concluded with these words:

"If while speeding down the left lane, you should come upon his '92 Ford Taurus, do not expect him to pull over."

Survivors include two sisters and two brothers.