Restraint is rarely touted as a virtue in urban design. Often, instructors in the History of Urban Design tend to treat the subject as a series of Greatest Hits - of grand interventions by such magnificently meddlesome people as Andre LeNotre or Baron Haussman or Robert Moses.

Teachers in graduate seminars rarely show slides of, say, a Midwestern town and exclaim, "Look at how well the urban designers held themselves back!"

The blockbuster mentality makes the current master plan of Mission Bay, the 300-acre redevelopment area in San Francisco, all the more remarkable. Here, after all, is a giant canvas of largely undeveloped waterfront acreage in a major U.S. city. The first impulse (at least for eternal first-year design students, like myself) is to create a miniature city with a hierarchy of major and minor roads, a radial plan with diagonal streets, major and minor axes, formal green spaces with equestrian statues and topiary plantings - in other words, the whole nine yards of Beaux Arts planning, or its poor relation, the New Urbanism. The current master plan, which is the fifth to be done in 20 years, resists the temptation to make a grand statement, however. Instead, the plan by Johnson Fain Partners opts to impose a more-or-less regular grid over the area that corresponds, in the dimensions of the blocks, to the original 10 blocks of downtown San Francisco. And while the restraint of this plan may or may not seem intuitively like the most exciting or most elegant solution, a close examination of the program suggests that this is the most urbane and best integrates this former railyard into the cultural and business life of the larger city. Indeed, the history of planning efforts at Mission Bay shows the tensions between the need to integrate the area into the city, while creating a memorable place in itself. The site itself is also especially tempting for planners, because it sits at the crossroads of two grids: the commercial-industrial grid, on northeast-southwest coordinates, and a residential neighborhood, on north-south coordinates, immediately south of the commercial area. The first four of the five plans done in the past 20 years, in fact, succumb to the temptation to bring the grids together in dramatic juxtaposition.

The first plan, done 20 years ago by John Carl Warnecke envisioned a set of high-rise buildings (office and hotel) on either side of the Mission Bay Channel, which conforms to the commercial-industrial grid. The same plan pulled the north-south grid north of 16th street, to bring housing into Mission Bay. The density and height of the scheme aroused public opposition. In the I.M. Pei/WRT scheme of 1985, the designers attempted to maximize the waterfront by carving out an oval-shaped channel south of Mission Bay Channel; ingeniously, this channel, and the resulting island at its center, are the formal devices to divide the commercial grid from the residential grid. This plan was also opposed for its density. And like the Warnecke plan before it, the Pei scheme was largely lacking in open space along the precious bay waterfront.

The third scheme by the Mission Bay Planning Team, led by EDAW and Dan Solomon, is an elegant, Beaux-Arts design that provides a clear hierarchy of streets arranged around a linear park or "common." This scheme also sets aside some bayfront land for a linear park. Pleasing as a graphic design, the plan arguably may have created some confusion on the ground, however, because streets are frequently changing in direction. Those same diagonal streets also disturb the views of the bay that could otherwise be available with streets that run straight east and west. The subsequent Skidmore Owings Merrill plan of 1989 is an inelegant truncation of the Solomon-EDAW that reflects the consensus of public hearings. This plan offers a further elongation of the bay front linear park, while providing more space for commercial construction. New uses at Mission Bay, including a new baseball stadium immediately north of the site and a new campus for UC San Francisco, occasioned the fifth and current plan, this time by Johnson Fain Partners. The campus plan, which conforms to the larger scheme, is by the East Coast firm of Machado + Silvetti.

As part of a Willie Brown-endorsed ambition to create a "synergy" between a research university and bio-tech businesses in San Francisco, landowner Catellus donated 43 acres of Mission Bay to UC San Francisco. That acreage is located smack-dab in the center of the master plan. The great achievement of the scheme is to knit Mission Bay into the existing fabric of the city, rather than setting it apart as a separate "campus" or miniature city of its own. Faced with the difficulty of planning around a centrally located campus, the Johnson Fain team, led by principal William Fain, chose to organize most of the site with the north-south (residential) grid; the diagonal streets are limited to either side of the channel. Medium-to-high-density residential blocks (with densities averaging 110 units per acre) can be found both north and south of the channel. Happily, the plan preserves the common of the Solomon/EDAW scheme. A small traffic circle at the far west is the anti-climactic device that connects the two grids.

What is most remarkable about this scheme is how thoroughly the university campus has been integrated into the grid. This contrasts with the typical University of California campuses, which are master planned as separate cities and communicate poorly with the cities that surround them. In a competition winning scheme, Machado + Silvetti, has responded with a very urbane, non-hierarchical scheme that uses open spaces as the landmarks, rather than big buildings. Jose Begazo, Johnson Fain's project architect, has likened the campus design to residential blocks in Paris. Importantly, the Johnson Fain designers chose to base the new grid on the historic "vara" block, the same dimension of the first 10 blocks of the city laid out by Vioget in 1839.

A vara is a Spanish linear measure equal to 2.75 feet. The vara block is 100 by 150 varas, or 275 feet by 413 feet. Johnson Fain principal William Fain argues that the vara block, beyond its historic associations, has near-ideal dimensions for an urban block. The use of the urban Vara block, in fact, helps clarify, if clarity were needed, what precisely makes San Francisco the most walkable city in America: the dimensions of the grid. No longer an abstract issue, the dimensions of grid here become elements in the sensuous enjoyment of cities - providing the energizing sense of movement through a regular tempo of streets and blocks.

This new plan, by relying heavily on the grid rather than special effects, promises to extend the pedestrian experience of San Francisco to the newest part of the city. In a sense, the Johnson Fain/Machado Silvetti scheme could be described as the scheme that resists the temptation to be grand, and in favor of being appropriate. Whether or not college lecturers add Mission Bay to their teaching syllabi remains to be seen. Even so, the scheme is a quiet but convincing argument about the power of the grid.