In three years, the parking shortage in downtown Palo Alto will be nearly three times as bad as it is today as the problem spreads to Crescent Park and sections of Old Palo Alto, according to an analysis conducted by a group of downtown residents and unveiled this week.

The residents conducting the analysis are from Downtown North, where the issue hits particularly close to home. Living in one of the few downtown areas where street parking doesn't have time restrictions, they have seen the parking spaces on their blocks disappear in the recent years thanks to an uptick in office activity.

The situation is expected to get even worse in the coming months and years, as major new developments come online. These include the new Epiphany Hotel that will open at the Casa Olga building on Hamilton Avenue and at least three new four-story office developments within a few blocks of each other -- Lytton Gateway on Alma Street and Lytton Avenue, 135 Hamilton Ave. and 240 Hamilton Ave.

How much worse? That's the question that Eric Filseth and Neilson Buchanan have been trying to answer over months of surveys and number crunching. They pointed at the city's recent estimate that the city has a current parking deficit of about 901 parking spaces. Then they plugged in other variables, including the percentage of new office workers taking mass transit instead of cars, employee growth in existing office space and all the new projects coming online.

The analysis, which Filseth and Buchanan presented to the Weekly on Tuesday, indicate that even if 20 percent of the new employees take mass transit, a conservative estimate, downtown's parking deficit will rise to 2,500. This also assumes that offices will have an employee for every 250 square feet of space, a traditional ratio that many feel doesn't really apply to Silicon Valley's start-up culture. If the ratio is closer to one employee per 100 square feet, the parking deficit in 2016 would be even more dramatic more than 3,500 spaces.

The parking model, available here, is interactive and extensible. Users can plug in their own assumptions and see how the changes impact the parking intrusion. The model also considers ongoing city initiatives, including the introduction of a valet-parking program in the High Street garage.

In conducting the analysis and inviting participation, Buchanan and Filseth aims to help the city tackle what has recently become one of its most urgent and complex problems -- a parking shortage that is already bad and that continues to get worse. Residents from the Professorville neighborhood have been clamoring for years for a residential parking permit program that would set time limits for non-residents parking on their streets. Other neighborhoods, including Downtown North, have been calling for the city to hit the brakes on massive new developments until they come up with parking solutions.

The City Council, for its part, signaled its intent to address the problem by setting "future of downtown and California Avenue" as one of its top priorities for 2013. Staff is currently performing analyses on potential sites for a new downtown garage and on downtown's potential to accommodate new developments.

Buchanan said the goal of the study isn't to propose solutions but to identify the problem. He credited the city's transportation planners with conducting the initial survey, which indicated a deficit of 901 parking spots and identified those downtown blocks that are fulling inundated by cars during the lunch hours. This includes most blocks in Downtown North and a sizable portion of Professorville.

Buchanan said he's been surveying the neighborhood four to five times a month for several months and counting the number of cars parked on every block.

The model he and Filseth developed makes some broad assumptions, including the gradual spread of cars outward in a mostly even manner and the willingness of office workers to take lengthy walk to get from their cars to their work desks, a stroll that in some cases would be more than a mile. Though they say it's not uncommon for some employees to walk a long way to get to their offices from Downtown North (one person, who works at Lyfe Kitchen on Hamilton Avenue routinely parks in the residential neighborhood, Buchanan said), it remains to be seen whether employees would be willing to trek all the way from the Junior Museum and Zoo to University Avenue in 2016.

On the map, the model resembles an archery target with a series of semicircles, each bounded by El Camino Real to the west and the San Francisquito Creek to the north. The first arc, which represents 2014, shows a deficit of 1,366 cars and encompasses nearly the entire Professorville, indicating that the few blocks in the neighborhood that still have parking spots will not have them for long.

By 2015, the number of cars goes up to 1,858 and the arc spreads east, past Lincoln Avenue, in Crescent Park and south, past Embarcadero Road, in the south. The following year, with the car deficit at more than 2,500, the wave of cars runs over Crescent Park and intrudes further south, toward Old Palo Alto.

"There's no other place for the cars to go," Filseth said.

The report doesn't claim to have the definitive tally for downtown's future parking deficit, but it hopes to keep the debate going. Users can download the downtown model, add new developments as they come online, factor in city initiatives such as valet parking and challenge the model's basic assumptions.

Filseth and Buchanan also maintained that their intent is neither to blame the city for the worsening parking situation nor to propose the answer. It's merely to address a significant limitation of the existing debate -- the fact that the city has "no accurate view as to what we are dealing with here," Filseth said.

"The city needs to step in and contain the parking deficit before it gets worse," he said.