Stem-cell therapy and urban design have little in common, or so I thought, until I saw Dan Solomon's design for New Railroad Square in Santa Rosa.

One type of stem cell therapy, as you have probably heard, is to inject healthy cells into diseased tissue with the expectation that the good cells will drive out the bad ones. In other words, the healthy cells become the templates for the production of healthy tissue.

In the San Francisco architect's plan for the former rail yards in downtown Santa Rosa, the typical block from the older sections of Santa Rosa takes the role of the healthy cell. The imported block, with its small dimensions, helps weave the New Railroad Square project into the fabric of the historic downtown. And the imported grid does more, or "wants" to do more, than bring scale and order to an area lacking those qualities. When looking at this plan it is easy to imagine the imported grid spreading out beyond the borders of the New Railroad Square development and communicating its newfound energy to other downtown areas in need of similar re-ordering.

Proposed by a partnership of Creative Housing Associates of Los Angeles, The John Stewart Company and Equity Community Builders, New Railroad Square is a 5.3-acre mixed-use, transit-oriented project along the historic railroad line. The old station and at least two old warehouses survive, and they are happily being integrated into the project as housing and a parking structure, respectively.

The site is the city's former rail yard, which has become an industrial no-mans-land that separates the city's West End on the north and the Railroad Square shopping district to the east.  To the east lies the tracks of the proposed Sonoma Marina Area Rapid Transit (SMART) train, whose curving rail bed serves as the eastern boundary of this project. Further east still, beyond the project boundaries, is the 101 freeway, which also helps break down the sense of scale and urban form in the immediate area. Moving east from the 101 freeway, we find another event that interrupts the urban pattern with a blind wall: a 1970s regional mall. In short, the neighborhoods bordering the 101 freeway in downtown Santa Rosa are a catalogue of quasi-functional urbanism lacking easy connections.

The New Railroad Square site is wedge-shaped, which is awkward to develop. To fill the site in the most rational way possible, the planner has opted for three courtyard buildings, each of which occupies a city block. The southernmost courtyard, just north of Third Street, is a "flatiron" building with office and retail space. Between Fourth and Fifth streets, a multi-tenant "public market" will occupy the ground floor, while 68 affordable units are on upper stories. The northernmost block contains 118 market-rate townhouses, and their three-story size corresponds in size to existing row houses in West End. A new north-south street draws together the three buildings of New Railroad Square, with three related buildings: a dance theater, a public parking structure and loft housing. SMART and the developers approved a deal in October 2007 in which the developers agreed to buy the land from the transit agency for $2.5 million. Construction dates on the $100 million project have not been finalized, although the project is likely to be completed before the SMART train's first phase, which is due in 2014.

New Railroad Square is a small-scale version of rail yard redevelopment, which has become popular throughout the country, replacing the tangle of freight train tracks and rail spurs with dense, mixed-use development. The largest is probably the Atlantic Yards, the politically vexed project that Forest City is trying build in Brooklyn, N.Y., while Los Angeles and Sacramento are also pursuing similar projects. Making the Santa Rosa project possible in the first place is the SMART train, which would stretch from Cloverdale in the north to Larkspur on the Bay. (A quarter-cent sales tax to fund the system is on the November ballot in Marin and Sonoma counties.) It's an intriguing, if idle, thought that the train gave part of this city its original form more than a century ago, and that a new train, rolling on the same footprint, is the catalyst behind the latest event in the formation of downtown Santa Rosa.

The organizational power of the newly gridded New Railroad Square also seems catalytic. The site plan wants to spread east and break down the scale of very large-scale objects that impede free movement of pedestrians.

The idea of the grid "wanting" to spread may need a word of explanation. I mean to say the site wants to spread its order-making grid, just as the architect Louis Kahn would tell his students that elements in architecture "wanted" to do certain things. Kahn was not actually anthropomorphizing walls and roofs. Instead, when he said things like the "wall wants to become a ceiling," he meant the wall has a design potential that the architect should be aware of.

In a similar vein, the grid – one of the simplest urban design tools – wants to spread order throughout the disorderly elements in downtown Santa Rosa. A railroad crossing, in fact, is planned at Fourth Street. Existing underpasses connect pedestrians to either side of the freeway, while an underpass at Third Street beneath the mall provides a connection further east.

The big challenge here is the enclosed mall, which blocks the clear sight lines and visible order of a genuine urban grid.  The enclosed, street-blocking structure "wants" to be sliced through by Third, Fourth and Fifth streets. It would not be impossible to reconfigure the mall as an outward looking lifestyle center that could conform to the grid while gaining support, in turn, by new and existing foot traffic in Railroad Square.

Those are admittedly a lot of fantasies inspired by a single project, but good urbanism creates energy that spreads outward. It wants to drive out the bad, dysfunctional spaces. If the streets of New Railroad Square and the existing streets in Railroad Square want to unify downtown Santa Rosa, who are we to object?