Jane Jacobs is moving in on Pennsylvania Avenue.

Jacobs, older readers will remember, is the author of "The Death and Life of Great American Cities," a book that appeared in 1961 and completely shook up conventional city-planning wisdom. The death of cities, Jacobs convincingly argured, was cataclysmic urban renewal which replaced live but messy neighborhoods with dead but sanitary high-rise housing projects.

The life of great cities, Jacobs said, is the life on the street, things to do and to see, bustle and spontaneous encounters, realization that the city is not just building on a parking lot, but that, as Shakespeare put it, "the city is the people."

Don't take me literally. Jane Jacobs, who teaches in Toronto, is not about to pitch a tent in front of the National Archives. But the Pennsylvania Avenue Development Corporation is seriously thinking about it -- a music tent, a tent for exhibits and other entertainment, a tent such as the one that attracts happy crowds every night in front of the Pompidou museum of modern art in Paris or in the Teatro Tenda in Milan, with the magic excitement of traveling circuses.

There is much more, a whole, carefully thought-out program. The Jane Jacobs spirit has seized the Pennsylvania Avenue developers. "It's one thing to build a nice street," says Rita Abraham of the PADC staff. "It's another to have people come and use it."

Oddly enough, a deliberate, planned and financed program for what the French call "l'animation de ville" does not yet exist in this country. A few developers, to be sure, have discovered that a good butcher or florist can lift the image and sales of an entire shopping center, even if you have to support him with extra-low rents.

We also have a few animated, special attractions in some of our cities, notably the Cannery in San Francisco, Fanheuil Hall Marketplace in Boston and the Citicorp Atrium in New York. But most city administrators still believe that street vendors are a public nuisance, even if they sell flowers; that a street musician is a traffic obstacle, even if he makes people smile; that acrobats performing in a public park, as they do on that lovely square fronting the Pompidou museum in the Beaubourg in Paris, are a threat to law'n'order.

PADC, to my knowledge, is the first redevelopment authority to work out a plan for the animation of its public spaces even as they are still being built, the way you would develop a plan for landscaping and maintenance. PADC has recognized that it is important to attract people to fill shops, cafes, restaurants and exhibits at all hours.

Systematic animation is closely related to "cultural planning," a new concept developed by city planner Harvey Perloff and the subject of a recent conference in San Antonio, sponsored by the American Council of the Arts, the League of Mayors and others. The conference established without doubt that artistic activities of all kinds create jobs, contribute to stability and attract audiences who directly and indirectly, contribute revenues to the city far greater than what the city might pay to subsidize the artistic activities. To be effective, however, arts activities must be as carefully planned in relation to demand, access, and impacts as schools, firehouses, or playgrounds.

The first draft of "An Animation Strategy for the Pennsylvania Avenue Area" was recently completed by Roberto Brambilla, an Italian-born urban designer from New York.

Brambilla proposes to start animation projects immediately, while reconstruction of the avenue is still in progress, on the grounds that the excitement of construction, despite noise and dirt, is in itself a form of animation.

Building construction work is fun to watch and, with the help of posters, leaflets and slides shown kiosks on the construction site, Brambilla would inform the sidewalk superintendents of the design, and the purpose of the building and its relation to the overall Pennsylvania Avenue plan.

The proposal is carefully worked out so it keeps adding attractions as new office workers, hotel guests and shoppers start to use the burgeoning development. Some of the highlights among the Brambilla recommendations are: d

The aforementioned tent-theater on the now vacant and sodded Kahn site, opposite the Archives. The structure is to be up for about six years until apartments are built there. The tent is to be artfully lit at night and will feature a variety of cultural and recreational events.

A continuous slide show will be developed. It will be similar to Boston's brilliant and witty self-portrait, "Where is Boston," in which Bostonians of all colors, incomes and background tell you about the history and character of their city. Originally created for the Bicentennial, the nonstop Boston show now plays Quincy Market.

Brambilla will put such a Washington show into a 250-seat theater in the Willard Hotel when it is restored. The nearby Western Plaza, now under construction will feature a pavement of different-color marble depicting the L'Enfant layout of Washington.

A Vendor's Market in front of the FBI Building, similar to the old print market along the Seine, the coins and stamps market near the Champs Elysees and the bird and flower market on the Ile de Cite, all in Paris. The stalls would be free-standing, so flower girls cannot eavesdrop on FBI secrets.

Other open-air markets, offering international foods, such as have become popular recently in lower Manhattan, Boston and San Francisco, are to follow later.

The proposed pedestrain mall on 11th Street between Pennsylvania Avenue and E Street would serve as an international center for cultural, technological and commercial displays from different countries, international clubs and restaurants, a movie theater for foreign film showings and festivities.

All along the avenue, Brambilla suggests a row of 50-foot-high flags representing the 50 states of the Union. They are to reinforce the powerful vistas of the avenue which, in contrast to the much wider and architecturally homogenous Champs Elysees, lacks architectural or landscaping support. The flags should give the avenue a ceremonial effect. They will fly at night and be illuminated.

In addition there is to be a continuing program of concerts, street theater, games, happenings, star attractions, contests and prizes. Children's events are to include circus and acrobatic acts, pet shows, costume parades, kite-flying contests and puppet shows. The idea is to attract people who would not ordinarily come, particularly in the evening. Special events, such as star performances and evening concerts, are to be planned to bring teen-agers and older people together.

Ambitious as all this may sound, Brambilla points to several other American cities -- notably Baltimore with it's imaginative and hardworking Office of Tourism and Promotion -- where at least parts of such a program have been successful. Brambilla sees the pitfalls of emphasizing architectural design over human activity and managements, of extravagant first-cost with no money for maintenance, as exemplified by the ultimate of horrors, Washington's inspid "Streets for People" in front of the Martin Luther King Library and the National Portrait Gallery.

To avoid such costly fiascoes, successful animation requires careful planning and adequate funding to cover the administration and operation of the program. The ideal agency for this, Brambilla says, would be a separate nonprofit organization -- something like Friends of Pennsylvania Avenue -- which can raise funds from different sources for general and specific expenditures.

The animation proposal is supplemented by a study by architect Jospeh Passoneau, recommending special tree-plantings and pavements for the Pennsylvania Avenue sidestreets.

Barring war, pestilence or a depression, much of this plan is likely to be carried out over the next 10 years if the PADC's newly appointed temporary board chairman, Thomas F. Murphy, former president of the bricklayers' union, goes along.

Who would have thought that we would ever have an animated avenue?