In its latest statement, the New Zealand Transport Agency (NZTA) said three steering group workshops were held with attendees representing key stakeholders late last year.
The workshops were to further develop the favoured option into what are now the proposed improvements and resulted in the clearway option being removed, the statement said.
"The proposed improvements for the Central Corridor are currently in the detailed design phase, which is expected to be completed by July 2019."
The statement said the detailed design, once complete, would provide a greater understanding of the deliverables, timing and funding requirements.
"Once this phase is complete we'll know more about funding requirements, as well as potential timing and delivery expectations."
NZTA said the project would "enable the further growth and revitalisation of business and tourism in the city centre".
Two public drop-in information sessions are being held on Wednesday for people who would like to learn more about the proposed improvements.
They will be held at the former Bendon Store at Rotorua Central Mall to update residents and businesses on the proposed improvements.
Work includes walking and cycling improvements, as well as safety initiatives, to enable the further growth and revitalisation of businesses in the city centre.
A recent Rotorua Lakes Council committee agenda said the Central Corridor was progressing through to local engagement and design finalisation.
It said tenders for the $11m project were expected in "mid to late 2019".
Once the works are complete, ownership of the state highway will be handed to the council to manage as a local road.
Rotorua Lakes Council infrastructure general manager Stavros Michael said the council was continuing to work with NZTA on the project which is part of the district's Connect Rotorua programme.
"The next steps in this project will be to update key stakeholders and the wider community and work towards final designs. The timing for tenders has yet to be finalised.
"Council must assess the state of the current assets (pavement, footpaths etc) and determine what work needs to take place as part of the upgrade to ensure that we are receiving an asset that is up to standard and fit for purpose for the expected lifespan of the assets."