For downtown residents who have watched their streets transform into commuter parking lots over the past decade, the trial of the century will begin next month.

That's when the city launches what is known as the Residential Preferential Program. That's also when officials expect commuters who for years have been parking their cars on the residential streets of Downtown North and Professorville to radically shift their behavior -- though no one is quite sure exactly what this shift will look like.

"We're going to see drastic changes in parking habits," the city's Transportation Planning Manager Jessica Sullivan told about 60 people who attended a public meeting at City Hall on Tuesday. "I know there's a huge fear of, 'It's going to be the same thing. People will buy permits and park close to downtown and nothing will change.' I'd be surprised if nothing changes. When you introduce pricing to any parking system, behavior changes dramatically."

The program was prompted by years of complaints from downtown residents whose blocks are routinely used by area employees who prefer to avoid the two- and three-hour parking restrictions prevalent in downtown's commercial core. The thriving downtown economy has worsened the problem, with separate surveys conducted by city planners and citizens showing numerous blocks oversaturated with cars during the weekdays hours. In some cases, the number of cars is greater than the number of parking spaces, which connotes both congestion and creativity.

But even though the new program aims to provide some relief by making workers buy permits, anxieties persist. Some residents at Tuesday's meeting wondered whether the first six-month phase of the program would have any effect and called for the city to impose more stringent limits on permits sold to employees.

Others wondered whether the new restrictions would just push cars to areas outside the permit area, which is roughly bounded by Palo Alto Avenue on the north, Lincoln Avenue on the south (a small portion of the district, between Alma and Bryant streets, juts out south past Lincoln, to Embarcadero Road), Alma Street on the west, and Guinda Street on the east.

One goal the program is almost certain to achieve is the removal of cars that belong to Caltrain commuters or Stanford University students from residential streets. Because these riders will not be eligible to receive permits, they will lose their ability to park for free in the neighborhoods and then proceed to their destinations.

The only people who would be able to acquire permits will be residents and downtown workers. Employers would also have to be registered in the city's new business registry to be eligible for permits.

As the program's name implies, residents will take priority. Each household will be able to acquire up to four free permits with an option of buying visitor permits for $25 each. Employees will be able to buy permits to park on the residential blocks for either $233 or $50, depending on income level.

The city will begin selling permits online on Aug. 15 and buyers will be required to show proof of downtown residency or employment, said Sue-Ellen Atkinson, the city's parking operations lead. They will be available at cityofpaloalto.org/parking.

Both residents and employees will have to start displaying their permits starting Sept. 15. After a two-week warning period, cars that don't have permits and that park in the permit district for longer than two hours will be subject to a $53 citation. The program will be enforced by Serco, Inc.

The new parking restrictions will be in effect from 8 a.m. to 5 p.m. between Monday and Friday.

In most cases, the permits would have to be affixed to vehicles. But the city will also offer hang-tag permits that residents' visitors and downtown employees will be able to hang on their mirrors and transfer to other drivers.

"Someone who works in the morning can use it in morning and then transfer it to someone who works the afternoon shift," Atkinson said.

Residents and employees will have the option of buying a day permit for $5. This means workers who usually take the train to work but need to drive once in a while will be able to buy the one-day passes and park on the streets.

Once in place, the program would address an issue that over the past three years has received more attention from the City Council than just about any other. To address downtown's parking shortage, the council has recently formed the Transportation Management Association, a nonprofit to work with employers to reduce reliance on cars; approved an expansion of city-run shuttles; introduced valet programs at downtown garages; and began planning for a new garage.

Yet no single measure has attracted as much effort or scrutiny as the parking-permit program. The city's previous effort to establish a parking-permit program focused on a portion of Professorville and fizzled in 2012, after a backlash from residents who argued that the program would only bump the problem to the adjacent neighborhood.

The new program targets a wider area and includes a larger array of permits and options for residents and workers. It was designed after nearly a year of meetings by a stakeholder group that included downtown residents and employers. And while the prior program died at the dais, the new one was unanimously approved by the City Council in December.

The city plans to evaluate the results in the first phase and then consider whether to cap the number of permits sold to employees in the next phase, which is set to begin on March 30. Sullivan also said that it's likely that in the future, the permits would designate which specific blocks the cars can park at, thus ensuring that employees' vehicles are spread out throughout downtown. These restrictions do not, however, exist in the first phase.

Resident Deanna Dickman was one of several residents who suggested that the program would be more effective if the number of permits designated for employees was limited from the start.

"As we grow, as more people belong to the business registry and as more and more are registered, there is more and more opportunity for them to buy permits. ... It's better to cap it. We'd feel secure," she said.

Dickman also pointed out that without color zones or any types of mechanisms to ensure non-residents' cars are dispersed, most employees will choose the blocks closest to the downtown core.

"That means all the blocks closer to downtown will have all the workers," Dickman said.

Other audience members suggested that drivers may seek solace in residential neighborhoods just outside the boundary. The program would thus shift the problem rather than solve it.

Sullivan noted that the city will pay attention to the changes in driving behavior and factor them into the design of the second phase. The entire program, Sullivan reminded the audience, is a trial.

"We're really trying to focus on the fact that this is a trial and it's absolutely open to change," she said. "If it turns out several hundred people are parking outside the boundary and impacting the neighborhood, this will be evaluated," Sullivan said.