A decision to add kerb extensions, a pedestrian crossing and signs to a main Rotorua connector road could see Rotorua Lakes Council defending itself in the High Court if it receives final sign-off on Thursday.
The three options were to keep the street as it was; install traffic management features such as chicanes or road narrowing; or close the road to through-traffic near the western, residential end.
The consultation prompted Baars' petition, which opposed any changes being made to the street.
Baars' petition attracted 680 signatures while a residents' petition calling for changes collected 57. The consultation closed on July 31 this year and showed an overwhelming majority of submitters - about 88 per cent - supported keeping the status quo.
However, at the November 5 Operations and Monitoring Committee meeting, council officers recommended a "modified status quo" - introducing four sets of kerb extensions, a pedestrian crossing and signs advising motorists of the residential area.
An amendment to leave the street as it is, suggested by councillor Sandra Kai Fong, was narrowly defeated, with a split vote that was broken by the casting vote of the committee's chairwoman, councillor Tania Tapsell, who opted for the modified status quo.
That meant on Thursday the council was to make a final decision whether to adopt that recommendation or not.
In Baars' letter - sent to mayor Steve Chadwick, all councillors and the council chief executive Geoff Williams - Holland Beckett lawyer James McDougall said most of the feedback on changes to Marguerita St supported "the literal status quo".
The purpose of the letter was to "challenge councillors' rationale and logic" and to "put [them] on notice".
If the council opted to implement the Operations and Monitoring Committee recommendation, Baars would refer it to the Ombudsman for investigation or for judicial review in the High Court "on the basis that it will be unreasonable, procedurally flawed and illogical", the letter said.
"What is deeply concerning is that [the] council has extensively consulted ... on three specific options and then recommended implementation of an option which was not actually consulted on, which disregards community views and is illogical and ineffective.
"These changes to the road layout are ineffective at addressing the residents' concerns of noise and vibration and do not solve any perceived or actual concern of the public."
"[Councillors] should use your good conscience and logic to vote against the recommendation."
On Tuesday, Baars told Local Democracy Reporting the proposed kerb extensions would disincentivise traffic on Marguerita St.
His lawyer, James McDougall, said on Wednesday the proposed modifications had no support from the public and made "no rational sense".
"It appears council staff and half the councillors are ignoring their own feedback process and are failing to exercise independent judgement to identify whether installing kerb extensions address residents' concerns.
"Any decision to modify the road without evidential support, or based on incorrect assumptions, is highly likely to result in [the] council being required to repeat the consultation and decision-making process."
He said there was no evidence the proposed modifications would alleviate noise or vibration issues which were "the primary concern of residents".
He said kerb extensions would also create unintended safety issues which he believed had "not properly been assessed".
On Wednesday, council chief executive Geoff Williams said the matter would be before the council on Thursday it would be "inappropriate to pre-empt final discussions and decision-making".
"[The] council will respond to the correspondence received in the appropriate manner, rather than through the media."
Local Democracy Reporting also asked what the proposed changes would cost to implement, and how much consultation regarding Marguerita St had cost to date, but answers to these were not provided.