Passenger transport executive, Merseytravel, has retained its certification for the international standard for Environmental Management Systems.
Following an independent audit, Merseytravel had to demonstrate that it was working to limit its environmental impact, is training staff, complying with legislation and delivering continual environmental improvements.
Cllr Mark Dowd, chair of Merseytravel, said: "We were the first passenger authority in the country to gain this certification six years ago and the environment remains very important for our future transport plans too. We will keep looking for ways to improve."
Neil Scales, chief executive and director general of Merseytravel, said: "We have led the way on environmental stewardship since we became the very first passenger transport body in the country to produce an Environmental Strategy thirteen years ago.
"That strategy and the ongoing commitment from our staff, partners and contractors continues to be an important element of all we do. To be reaccredited in 2009, Year of the Environment, makes the achievement that extra bit special."
Two projects over recent years, Liverpool South Parkway and the Pier Head Ferry Terminal, have been built with environmental stewardship at its foundations.
Both are rated as "very good" BRE Environmental Assessment Method standard buildings, using elements such as rain water harvesting, geothermal heat pumps, roof insulation or solar cells.
Merseytravel is working with Neptune Developments and Countryside Properties and contractors BAM to achieve BREEAM "excellence" for its new headquarters in Mann Island.
BRE Environmental Assessment Method is a voluntary measurement rating for green buildings that was established in the UK by the Building Research Establishment.
Merseytravel's latest news comes in the same year it also achieved the Carbon Trust Standard in January.
Merseytravel's carbon footprint has dropped by 7% since 2006 through a series of measures. These include running Mersey Ferries at slower speeds, fitting new computerised energy control systems in Merseytravel offices and the installation of variable speed motors and drives for the giant ventilation fans at the Mersey Tunnels.