Portsmouth City Council has been awarded £1.5 million from the government to upgrade 105 of the city's buses so they meet the Euro VI emission standard.
Buses which travel through specific areas of the city have been selected to receive new greener exhaust systems to improve air quality.
A ministerial directive issued in March placed a legal duty on the council to achieve compliance with national air quality targets in two specific areas: Mile End Road and Alfred Road.
Starting in April, the council will work with local bus operators Stagecoach South and First Solent to retrofit exhaust systems to reduce nitrogen dioxide and particulate matter.
The following services have been identified to receive the upgrade: First Solent 1; 2; 3; Star 7 and Star 8, Stagecoach 20 and 700. The council's own Park & Ride buses are also included in the scheme.
Cllr Dave Ashmore, Cabinet Member for Community Safety and Environment, said. "Retrofitting these buses will have a huge impact on reducing vehicle exhaust emissions. This project will not only benefit these road links, but will also have wider air quality benefits as the retrofitted vehicles will travel along the other roads in the city.
Although the ministerial directive focuses on Mile End and Alfred Road, as a council we are looking at measures to benefit all areas in the city, such as the London Road area, for example."
Edward Hodgson, Managing Director for Stagecoach South said: "We are delighted to be working with Portsmouth City Council on this exciting project. Air Quality is something that affects us all and bus travel provides a much greener way to travel in and around the city with substantially lower emissions per passenger kilometre compared to using a private car.
In late 2017 Stagecoach invested in 20 brand new Euro 6 buses for city Route 23 and it's great that we can now follow this with exhaust upgrades to the remainder of our fleet serving Portsmouth."
First Solent Interim Managing Director Simon Goff said: “We are completely committed to supporting the cleaner air strategy in Portsmouth and are delighted to have the opportunity to retrofit our vehicles through this government funding. With the latest green exhaust system technology, we will be able to reduce emissions significantly. Greener buses mean cleaner town and city centres and a healthier environment for everyone."
The proposed upgraded technology to be used for each bus is designed to significantly reduce harmful emissions such as nitrogen dioxide, diesel particulates, carbon monoxides and hydrocarbons.
The programme is due to be completed by the end of 2019.