Eight carparks immediately in front of the library are set to be lost to enable a pedestrian crossing to shift along Beach St and away from a corner.
Transport officials have said changing the road layout should improve safety.
Port Chalmers resident Anna High said the proposed move took people by surprise.
"We were first told of it as residents when it was a done deal," Dr High said.
Removing the eight parks could have a detrimental effect on the library as a community hub and the benefits had not been made clear to residents, she said.
"It will certainly dramatically impact access to the library in a really tangible way.
"After school and at peak times, those parks are all full."
However, Port Otago chief executive Kevin Winders said the new alignment, including the location of the pedestrian crossing, should be safer.
Background to the changes included accommodating an extension to the Port Chalmers Maritime Museum and enhancing the environment in the vicinity, he said.
The existing crossing was on a right turn from George St, State Highway 88, and there had been near-misses there, he said.
The port had advocated for a shift of the crossing towards the railway line for some time.
This would enable pedestrians to cross safely between the maritime museum and the library, Mr Winders said.
A Dunedin City Council spokesman said the planned layout changes resulted from a project led by Port Otago, alongside NZ Transport Agency Waka Kotahi, and the council provided feedback to it.
Feedback from the project was that the new road layout would be safer for vehicles and pedestrians, including cruise ship passengers.
"We are also confident that the loss of parking outside the popular community library has been offset by Port Otago providing 12 additional unrestricted parks nearby on Beach St, toward Careys Bay."
A transport agency spokeswoman said the road layout changes were approved in principle between the agency and the council’s safety engineers.
Dr High, a University of Otago law associate professor, was not persuaded a strong case had been made to shift the crossing.
She believed visibility for the existing crossing was fine.
Dr High expected parking at the northwestern end of Beach St and then navigating a busy intersection to get to the library would be "tricky" for people with children and babies.
West Harbour Community Board chairwoman Ange McErlane was also unconvinced moving the crossing would improve safety and she said people were upset about lack of consultation.
Cr Carmen Houlahan said a lot of people had been in touch with her about the issue.
She described them as livid.
"Users of the library are not happy at all," Cr Houlahan said.
The city council is running consultation this month about parking time restrictions.
"It is important to note that this is a consultation on the time restrictions for the new parking only, and not for road design as this is finalised and awaiting construction," the council’s website said.
Council images showed the space for eight parks was taken up by an adjusted disability park and the proposed crossing.
Three formal parks would be created on road reserve on the other side of Beach St.
It is proposed eight parks further along will have 30-minute time limits, instead of being unrestricted.
Mr Winders said the port had previously built a new carpark for staff and the refurbished museum would reopen later this year.
