San Francisco, a memorable city in one of America's most dramatic settings, is conducting a bold experiment. Concerned with both the quality and quantity of recent downtown development, the city has adopted the nation's, if not the world's, most radical plan for controlling urban growth.

By far the most revolutionary aspect of San Francisco's new plan is its office space quota.

In 1985, the San Francisco Board of Supervisors mandated a citywide, annual ceiling of 950,000 square feet of new space for 1986. For 1987, voters halved the quota to 475,000 square feet, and it can be changed again only by the electorate.

The original ceiling originated from market studies projected to the year 2000 and was only slightly less than the city's annual office space absorption rate over the past 20 years. Obviously, voters transmitted an even stronger no-growth message with their 1987 quota vote, despite a 16 percent citywide office vacancy rate discouraging new construction.

Under the new regulations, developers must compete for scarce space allotments. The powerful City Planning Department and Commission evaluate competing proposals, for which the ordinance specifies seven criteria. One of the criteria -- does the city need more space? -- keeps the municipal government in the market analysis business and, according to a developer, "takes away a developer's right to go broke" on his own site.

But another criterion -- does the project possess architectural merit? -- led to a so-called "beauty contest." In the spring of 1986, a design review panel of three architectural educators assessed buildings competing for space under the quota. They reported that "none of these projects fully demonstrates the downtown plan's potential to produce better buildings. . . . None is brilliant and none is an awful embarrassment."

Given such judgments, plus the planning department's conclusion "that no compelling need existed for new office space at the time," the City Planning Commission rejected all proposals.

In San Francisco, matter-of-right zoning is no more.

Until two years ago, San Francisco was like many cities. It had been transformed in recent decades by the minimally orchestrated interaction of economic and market pressures, private property speculation and questionable zoning practices.

Emulating New York, the city had adopted incentive zoning in the 1960s; developers received density increases in exchange for such project amenities as plazas and mass transit access. But experience showed that these trades were not always great deals.

High-rise office buildings shot up and completely altered the historic, hill-hugging skyline. Often fronting on narrow streets, tall buildings cast long shadows, produced gustier winds and generated more traffic congestion.

The architecture of many new downtown buildings looked regionally neutral; most projects would be appropriate anywhere. Few seemed native to San Franciscans, who saw themselves being "Manhattanized."

Consequently, believing the city's unique visual character to be threatened, San Franciscans insisted on a totally new downtown plan, which was approved in the fall of 1985.

According to Dean Macris, San Francisco's planning director, the new plan will "compel participants in the building process -- especially architects -- to consider the qualities that make great cities . . . livable."

He notes that "in a world where cultural styles and tastes constantly move toward the center . . . where building materials and technologies are universally applicable, it seemed especially important to shape design guidelines in ways that emphasize San Francisco's uniqueness."

What are the essential elements of San Francisco's new plan? In addition to citywide office space limits, there are four other strategies. All are carried out through legislative rules, not through zoning incentives or "loosely worded" guidelines. A primary goal of the new plan is the preservation of significant structures with notable historic, architectural or contextual value. The city's historic landmark designation process, dating from the 1960s, was deemed weak and inadequate.

According to Macris, six or seven downtown landmark buildings were being razed each year.

Today, following a comprehensive survey by the planning department and a private preservation group, 240 buildings have been declared untouchable, blessed by mandatory preservation.

Another 190 buildings in six downtown conservation districts have been declared "supportive of the district's architectural character."

Preservation of these "contributory" buidings is encouraged, but not required. However, with their zoning potential diminished substantially, these properties are likely to remain.

The adopted plan constrains growth in overbuilt areas while earmarking for development other areas considered more adaptable to or in need of change. Developers can transfer existing development rights -- for increased density and height -- from properties in areas to remain unchanged and apply them to properties in development districts.

San Franciscans, openly critical of downtown architecture -- towering, box-shaped office buildings with flat tops and superscaled bottoms relating poorly to the scale of the street -- lowered height limits and allowable floor area ratios. (FAR is the ratio of total building floor area to the size of the lot.)

In the densest district, the FAR dropped from 14 to 1 to 9 to 1. In the retail district, modified height limits match prevailing building heights "to reinforce the consistency of the existing street wall and cornice lines" and "to retain the open, sunny environment." Buildings also must taper as they go up, both to avoid flat-topped boxiness and to improve access to sunlight and sky. To encourage Believing the city's unique visual character to be threatened, San Franciscans insisted on a totally new downtown plan, which was approved in the fall of 1985.

slender tops, the plan grants a 10 percent height-limit bonus if it is offset by a decrease in the area and volume of upper floors.

Open space -- without density bonuses -- is required, either on or near the site, but not more than 900 feet away. For every 50 square feet of office space, developers must provide one square foot of outdoor open space.

Also, shadow and wind studies are required for major projects; under normal conditions, ground-level wind speed cannot exceed 11 miles per hour.

Potentially among the most controversial of San Francisco's new rules is the "exaction" program, applicable to new office buildings that are more than 25,000 square feet in size.

For each square foot of office space, sponsors must pay fees: $5 for housing, $5 for transit improvements, $2 for park space, $1 for child care unless it is included in the project and 1 percent of the total cost of the project for public art.

Thus, the total exaction can exceed $15 per square foot of office space, over and above all other project development costs. And these fees are not necessarily earmarked for public improvements needed only because of new projects.

Exactions have been challenged in court with the claim that they are taxes, not fees. The city's position has been upheld so far by lower courts, but nearly $30 million collected for transit improvements remains in escrow pending further litigation.

Planner Macris believes that exactions, as an additional front-end capital cost, oblige sellers to lower the price of the site for office development to offset purchasers' increased costs.

Otherwise, projects on such sites would be unable to compete with developments outside the downtown area, or with projects smaller than 25,000 square feet, which are not subject to exactions.

However, architects and developers think otherwise, suggesting that exactions, along with some of the other rules, are indeed discouraging new construction. And some consider them fundamentally unfair, placing a disproportionate financial burden on newcomers for solving citywide urban problems, the cost of which should be shared more equitably.

San Francisco's experiment has just begun. It raises scores of legal, economic and aesthetic questions.

How well it works remains to be seen, but its success or failure is being watched elsewhere by countless governments under siege by constituents voicing the same complaints about unchecked growth that prompted San Francisco's drastic solutions.

NEXT: Testing San Francisco's plan. Roger K. Lewis is a practicing architect and a professor of architecture at the University of Maryland.