SPEED limits on sections of Cleveland-Redland Bay Road are to drop by 10km/h to 60km/hr and 70km/hr in this month.
In a statement, the Main Roads Department said the changes - which would come into effect on March 16 - came after a speed limit review and were designed to improve motorist safety.
"Works will include replacement of speed limit signs and, prior to this, variable message signs advising of forthcoming speed limit reductions," the statement said.
Signs were set to be replaced starting from March 16 and finishing by March 20, depending on weather conditions.
Standard sign replacement hours would be from 6am to 6pm but works might be undertaken at night for the safety of the workers and drivers and to minimise the impact to the road network.
TMR said the speed reductions would improve motorist safety on Cleveland-Redland Bay Road and any additional travel time would be negligible and offset by reduced delays overall due to fewer accidents.
"Due to traffic management activities designed to protect workers during signage replacement, nearby residents (and) businesses may experience short-term impacts including delays.
"TMR appreciates your patience while these important works are being carried out and will make every effort to minimise disruptions during this project."
Bowman MP Andrew Laming and Redlands LNP candidate Henry Pike took aim at Labor for reducing speed limits rather than investing in roads.
"I am all for safety, but these changes are just a green light for more speeding infringements on what is fundamentally a long straight and safe road. This road needs upgrades, not reduced speed limits," Mr Laming said.
"This Labor government continues its attack on car owners, through rego hikes, building bus stops instead of better roads and now reduced limits instead of increased investment.
"I am horrified that (Redlands MP Kim Richards) personally ticked these reductions off, without involving locals."
Ms Richards said road safety experts, rather than MPs, made decisions on speed limits.
"Speed limits are decided by a Speed Management Committee made up of TMR, Queensland Police Service and Redland City Council officers," she said.
"Is Andrew Laming suggesting he knows more about road safety and speed limits than a local police officer or a road planner?"
A TMR spokesperson said there were 148 road traffic crashes recorded on Cleveland-Redland Bay Road from 2014 to 2019.
"This included three fatalities, 58 hospitalisations, 69 injuries requiring medical treatment and 18 minor injury crashes.
"We do not typically undertake public or stakeholder consultation when carrying out speed limit reviews. The review is solely based on technical information with the objective of improving road safety."
Ms Richards said the total cost to upgrade Cleveland-Redland Bay Road was about $400 million.
"The Palaszczuk Government has $42 million in its budget to duplicate the road and work will start soon at Anita Street," she said.
Changes to speed limits
- South of Bay Street, Cleveland to south of South Street, Cleveland - down to 60km/h
- Boundary Road, Victoria Point to south of Benfer Road, Victoria Point - down to 60km/h
- South of Benfer Road, Victoria Point to near Giles Road, Redland Bay - down to 70km/h
- South of German Church Road, Redland Bay to south of Serpentine Creek Road, Redland Bay - down to 80km/h
TMR said drivers should be aware that these locations were approximate and should look for and observe speed limit signs.