Douglas N.Schneider, a man who acted on his conviction that cities belong to people and not to automobiles, resigned yesterday as director of the District of Columbia's Department of Transportation.

Schneider's resignation, effective in August, was accepted "with reluctance" by Mayor Barry. Nonetheless he will be rid of a man who was controversial and a man some motorists loved to hate. For it was Doug Schneider who:

Bitterly opposed right turns on red until he was forced by the federal government to adopt it, then put up "No Turn on Red" signs at four out of every five intersections in the city.

Mounted a vigorous attack against illegal parking here and, when he could get little cooperation from the police department, created his own ticket-writing force to wage the war.

Infuriated Montgomery County commuters by returning 13th Street NW to two-way traffic. It had become a one-way rush hour freeway and "that street really belongs to the neighborhood," Schneider said.

Was one of the first urban transportation directors in the country to reserve curb lanes on major thoroughfares for buses, and thus attempt to make public transit more convenient than cars.

Battled vigorously for low fares on Metro, arguing low rates were needed so transit could compete with the auto driver, who he described as overprivileged, over-subsidized and overpampered.

Supported the use of almost $2 billion in federal money for Metro subway construction, money that could have been used for freeways and other road-building projects in the District of Columbia.

Schneider, 48, could not be reached for comment late yesterday. A press release from the mayor's office said that Schneider is "seeking to change to a new perspective and different working environment."

Schneider himself has told friends in recent months that he was getting a little tired, even bored, with his job, which he has performed with verve and decisiveness since July 1975. He was appointed by Mayor Walter Washington as the first director of theDepartment of Transportation, was retained by Mayor Barry, and was highly regarded by transportation professionals as somebody who could get things done in an immensely complex local bureaucracy.

His views of urban transportation were spelled out clearly in an interview in 1975, just before he took charge of the department. "I think it's immoral," Schneider said, "for somebody to drive a car downtown." The quote never appeared in print, because Schneider jocularly threatened bodily harm to a reporter if he used it. The reporter told Schneider he would use it the day Schneider quit.

The public, particularly the auto-driving one, no doubt perceived that those were his views as the years passed. Schneider regularly was attacked by the American Automobile Association and suburban commuter groups for what they perceived as shoddy attention to the needs of drivers.

Early in his administration, he moved his traffic engineering department from a nice office overlooking 12th Street NW to an underground bunker hard by the 3rd Street expressway. He installed his mass transit director in the office with the nice view.

To Schneider, the urban freeway had become the ultimate symbol of irrational transportion planning. He told Post reporter Paul W. Valentine in 1978:

"What sense does an urban freeway make? It takes up space in an already crowded area. It removes land from the tax base. It's ugly. It destroys the city esthetically. It creates pollution, it cuts off urban dwellers from city services. But more important, it fails to accomplish its objective. fIt doesn't relieve congestion. It just generates more cars. It may move the congestion around a little bit, but it sure as hell doesn't solve the problem."

From that position, he moved logically to the belief that public transit was a requirement for a city to work. "Once we have made this enormous investment in improving our transit system," Schneider said, "it is silly to continue to permit the automobile to dominate." He set about changing that.

Schneider was keenly sensitive to the needs of the black constituency of the District of Columbia. His frequent impassioned pleas for low Metro fares always cited the poor and the transit-dependent of Washington.

As one of D.C's two members on the Metro Board, Schneider would tell his suburban colleagues:

"We know from the urban riots, we know from Watts that transportation, mobility, was a key issue. There are jobs in the suburbs, too, and we have to get our people to those jobs."

There was no word yesterday on what Schneider, a lawyer, will do. "He has talked about trying to make some money," a friend said. "He has at least one child in college."

Schneider's job pays $50,112 annually. There was no immediatge speculation on who his successor will be.