London Underground upgrader Tube Lines exceeded its carbon reduction target in 2009, increasing its carbon savings by 20% on 2008.
The heavy engineering company is involved in the multi-billion pound improvement works on the Jubilee, Northern and Piccadilly lines.
Between 2008 and 2009 1,002t of carbon was saved, the equivalent of one passenger travelling end-to-end on the Piccadilly line 243,194 times.
Head of Environment at Tube Lines Steve Judd said reducing emissions may be difficult but it makes good business sense.
"Better management of our resources drives costs down and allows us to do our work for the travelling public more economically and efficiently," Judd said.
The company's commitment to these savings is set to continue into 2010 with a pledge to cut another 1,000t.
Reductions made at Tube Lines' head office and training centre accounted for a further 607t of CO2.
Overall 6,279t of carbon has been saved, enough to fill Buckingham Palace 11 times over.
Escalator refurbishment has helped save 166t at three stations alone by only replacing parts that are faulty or have reached the end of their useful life.
Recycling aggregate used to retain walls has saved a further 53t, while Tube Lines has teamed up with the Woodland Trust to plant 200 trees.