The ubiquitous corporate shuttle buses that have become a symbol of gentrification in San Francisco will continue operating as is for another year — at which point the controversial program could face a major overhaul.

That’s the takeaway message from a tentative deal reached Monday between three members of the Board of Supervisors — representing the board’s progressive and moderate factions — and four major tech companies that rely on the buses to transport thousands of workers daily between San Francisco and Silicon Valley.

The tentative agreement lays out the conditions under which the shuttle bus program will continue for another year while indicating potential changes in the future.

Most significantly, it caps the number of locations that the buses can stop at to the current 125. If the number of buses that stop at each location increases by 50 percent or more, a mandatory air quality assessment would be triggered. And it requires the Municipal Transportation Agency and the San Francisco County Transportation Authority to study transitioning the program to a hub model where riders would get on and off the buses at a set number of locations. It also commissions the budget and legislative analyst to study the impacts of commuter shuttles on neighborhood displacement.

Present at the negotiations were Supervisors London Breed, a moderate, and progressives David Campos and Norman Yee. The tech companies present were Genentech, Facebook, Apple and Google. Also taking part in the negotiations were representatives from the Service Employees International Union and the Sierra Club, which wanted to challenge the program through an environmental impact review.

The negotiations were triggered because a majority of the Board of Supervisors want to overhaul the program without approving such an exhaustive environmental review. The tech companies were forced to negotiate or face the prospect of the environmental impact review, which they want to avoid even more than the supervisors do.

But the companies were not happy to be at the negotiating table, given that the Municipal Transportation Agency’s Board of Directors unanimously voted in November to make permanent the 1½-year-long pilot program begun in August 2014 that allows the shuttles to share Muni stops, establishes shuttle routes and charges operators a fee.

The transportation agency required some significant changes in November, including limiting bigger shuttle buses to larger streets and requiring operators to use less-polluting buses. Even so, the supervisors criticized the agency for approving the program without sufficient analysis.

“The reason we have to step in as a board is because the MTA failed to analyze the various options, including the option of a hub,” Campos said.

“The MTA — they are transportation people. So they did a transportation job. It was all about transportation — period. They are not thinking about housing. We are looking at the whole picture. They are just looking at ‘How do we move things efficiently and manage transportation?’” Breed said.

MTA spokesman Paul Rose rejected criticism that the agency fell short.

“We did a thorough analysis of all issues within our purview and worked with other city agencies for guidance on issues outside our expertise. We look forward to working with the Board of Supervisors, the community and other stakeholders to finalize an effective and responsible commuter shuttle plan,” he said.

MTA officials, business leaders and shuttle operators have maintained that shuttles take cars off roadways and reduce congestion. Critics say the buses contribute to gentrification and the displacement of renters because the influx of tech workers has helped drive cost increases in the housing market.

Shuttle operators said they did not want to comment because the negotiations are ongoing. If the agreement is finalized and the MTA also signs on, the Board of Supervisors is expected to reject the appeal for an environmental impact review on Feb. 23.