The council is carrying out ‘essential signal upgrades’ at three major junctions in the city.
Residents are being advised that this work could lead to some overnight lane closures and drivers are being advised to allow extra time.
The first junction to receive the upgrade is the junction at Havant Road/Eastern Rd/Farlington Avenue.
Work began on Monday and is expected to last until Friday, November 22 and the council has said that it will improve traffic flow.
Portsmouth City Council have said that the roadworks will take place overnight and there will be temporary traffic lights in place, as well as potential overnight lane closures.
The work will take place between 7pm and 6am Monday to Friday and involves upgrading the traffic signals with sophisticated Microprocessor Optimised Vehicle Actuation (MOVA) technology and replacing the cable under the pavement.
Existing vehicle detection equipment will be replaced, and new low-level early-release cycle signals added to the junction.
The installation of the MOVA system will seek to improve traffic flow by generating its own signal timings depending on traffic levels, dispersing traffic as efficiently as possible. While the new cycle signals aim to improve safety for cyclists.
Councillor Lynne Stagg, Portsmouth's Cabinet Member for Traffic and Transportation, said. ‘As an island city with limited road space, we can't always create designated bus lanes.
‘By giving priority to buses, this technology will improve local bus journey times while maximising traffic flow to benefit other road users.
‘Keeping the traffic moving means we reduce congestion and improve air quality at busy junctions. The new signals are extra low voltage, so are more energy efficient too.’
The council have said that the roadworks are part of plans for a bus rapid transit network in the area.
Signals at the junctions of Copnor Road and Burrfields Road, and Fratton Road/Lake Road and St Mary's Road have also been selected for upgrades. All three junction improvement schemes have been selected based on proposed rapid transit routes.