Developers highlighted flexible parking patterns and dedicated community space at a public meeting on a Mattapan Square mixed-use project Tuesday night.

Around 40 attendees filled the Mattapan Library’s community room, where they were briefed by representatives of the development partners and officials from the MBTA and the Boston Planning and Development Agency (BPDA).

The development team – Nuestra Communidad Development Corporation and the Preservation of Affordable Housing Inc. (POAH) – which won rights to build on the sprawling River Street lot after a competitive process last year, is gearing up for the BPDA’s vetting 80 process.

“The design is iterative, and we’re open for your feedback,” said Julie Creamer, POAH’s vice president of new construction and special projects. Full designs are not yet complete as the developers wait on additional community input.

As presented, the design features a single building that crosses over a parking lot and rises six floors along most of the River Street portion of the lot and then to seven stories along the road closest to the Neponset River Greenway.

Given that the MBTA has specific requirements for transit access through the site, Creamer said, “we’re trying to get to a place where we’re all happy with what’s being designed.”

To that end, the team proposed a creative way to use the 50 ground-level parking spots needed for MBTA commuters. Architect David Saladik explained that 30 of the spots would remain accessible to T commuters – paid for by phone like other transit-specific parking – while another 20 would toggle in and out of availability during peak- and off-peak hours. This could free up space for farmers markets or other public community events when demand for parking is lower.

The development is encircled by bus routes and could include designated drop-off zones to smooth the flow of traffic. A joint pedestrian and cyclist path would frame the road’s outside edge. A change to the bus queuing location will ideally “minimize the impact of traffic on the area,” he said.

Saladik went over the preliminary designs, highlighting the project’s focus on community development, health and wellness, and social connectivity. The promised 135 residential units are still planned, with 52 percent of them reserved for those earning up to 60 percent of the area median income. Another 70 parking spaces for residents would lie in an underground parking garage accessible from the Gillespie Lane entrance.

The 10,000 feet of River Street-fronting commercial space would be a prime location for cafes, restaurants, or other local shops, the developers said. Creamer said Roxbury’s Haley House may be the type of tenant they would hope to see serving as a community hub.

Around 4,000 square feet of community space will fill the bottom floor of the building section closest to the Greenway entrance. Behind it is “enough space in the back here to create a fun landscape where kids can play, we can have seating, or you could have possibly other events,” Saladik said.

Community members posed questions on traffic, parking, local jobs, and project timing. Creamer affirmed that the developers are dedicated to making sure that the project contractor stays in touch with the community and meets the requirements for workers who are residents, women, and people of color.

From the time the vetting process begins, it is likely to take around 18 months to completion, Creamer said, but there is at this point no set timeline.