Bus Éireann now has 61 hybrid and three hydrogen buses operating on its national fleet enabling it to achieve what it refers to as 470,000 emission-free kilometres in 2022.
According to the company's second sustainability report, that represented a three-fold increase on the 150,000 figure in 2021.
The hybrid buses operate on routes in the cities of Galway and Limerick.
It also operates the only three hydrogen buses in Ireland on Dublin commuter routes.
Bus Éireann introduced Ireland's first all-electric town bus service in Athlone in January.
All of the zero or low-emission vehicles are provided by the National Transport Authority (NTA).
The company aims to halve its greenhouse gas emissions by 2030 and this year it expects to reach the milestone of over one million emission-free kilometres since the launch of its Sustainability Strategy.
"Bus Éireann, as Ireland's national bus company is leading the drive to make Ireland’s bus network more sustainable, and in doing so, to convince travellers to choose public transport over private cars," Stephen Kent, Chief Executive of Bus Éireann said.
"This year, we expect to reach the crucial milestone of delivering over 1 million emission-free kilometres," he added.
Passenger numbers on Bus Éireann services returned to pre-pandemic levels in 2022 with 89.5 million journeys taken, up over 50% on the previous year.
The company operated or contracted more than 225 million service kilometres last year across road passenger and school transport services. It operates the school transport scheme on behalf of the Department of Education, which now carries a record 151,000 children each school day, including 17,500 Special Educational Needs (SEN) students.
