Schaaf and Bauters both note that West Oakland, where Caltrans suggests many of the potentially detoured vehicles would be routed, already suffers disproportionate pollution impacts from highway, railroad and cargo ship traffic.

"This project would have had horrific impacts on the community," Schaaf said. "That amount of traffic and particularly truck traffic on our local roads would have been extremely disrupting, dangerous and polluting to our residents."

Bauters and Schaaf both said that in its presentations to date -- including two "encore" community meetings it held in Emeryville and Oakland earlier this month -- Caltrans has failed to lay out a case for why it needs to do the Maze project at all.

Bauters said the agency, which has suggested that high-load trucks are being diverted around the Maze to avoid the lower-than-standard overpasses there, presented no data on how many trucks might be involved or evidence that trucks have been striking the overpasses. The agency also conceded there are no structural concerns with the Maze that would require the proposed work.

"You don't have a structural deficiency issue," Bauters said. "You don't have a height clearance issue. So the only issue you could have is one of two things, in my opinion. Either you do have (traffic) that's being diverted -- but if you did, you'd have that data to justify your project. ... So what remains? There's a private agenda."

Schaaf said the need for the project remains "a mystery."

"We met with the Port of Oakland -- they were not aware of the project and certainly had not requested it to support their operations," she said. "I asked the California Trucking Association -- they were not aware, it was not something they had asked for. It truly was a mystery where the request for this project came from. So certainly the pain-versus-gain analysis did not make any sense to me."

Margaret Gordon, co-founder and co-director of the West Oakland Environmental Indicators Project, said the Caltrans proposal runs counter to a new state law, AB 617, that has created a new plan for cleaning up an area of the city long burdened by excessive pollution.

"You are putting a community, West Oakland, at harm when we are in the process under AB 617 to come up with an emission reduction plan," Gordon said. "So Caltrans -- what are you doing?"

Dave Campbell, advocacy director for Bike East Bay, said the Caltrans assessment of the projects has also failed to take account of how detouring Maze traffic onto local streets -- including San Pablo and West Grand avenues and 27th and 40th streets, among others -- will affect pedestrian and cyclist safety.

"My concern is that if you're putting more traffic onto these streets, you need to make them safer and better," Campbell said.

He also said the agency doesn't appear to have considered how people using Waze and other route-finding apps will behave when they're confronted with future detours.

"Keep in mind not everyone is going to honor those detours," Campbell said. "They're going to find the shortest route to where they're going, and their phone or their car tells them exactly how to do it. So Caltrans needs to study what are people actually going to do."

Caltrans did not respond specifically Wednesday to questions about gaps in communication with local officials and communities, about the lack of specific data to justify the project, or about whether it will undertake a new environmental assessment of the Maze project.

Tuesday, agency spokeswoman Lindsey Hart said the agency's pause on the Maze planning was to allow time for more local input.

"We heard from the community and the stakeholders that, 'Hey, we'd like some more time to really weigh in on this,' " Hart said. "And so we said, 'No problem, we'll go ahead and put a pause on the project for the time being.' "

Schaaf and others said that Caltrans officials, including the agency's District 4 director, Tony Tavares, have been responsive to the issues they're raised.

"Oh, yeah -- I've got lots of conversations now," said Gordon of the West Oakland environmental group. "I get lots of returned calls."

Schaaf said that as far as she's concerned, Caltrans' pause of the project means it's on indefinite hold.

"What I assume it means is that this project is off the active table," she said. "And if it ever comes back again, that Caltrans will do their due diligence, speak to the impacted communities and listen to us."

Correction: This story originally referred to John Bauters as Emeryville's mayor. He is the town's former mayor and now serves on the City Council.