Milwaukee County has finalized plans to purchase 136 low-emission buses over the next two years to replace about one third of the county's current fleet.

The old buses, which are past their useful lifespan of 12 years and / or 500,000 miles, will be replaced starting this March, with additional buses set to integrate in 2013 and beyond.

Funding for the new buses was provided by $36.6 million left over from an original $289 million in federal funds appropriated for area transit projects in 1991. Additional funding was provided by a $7 million federal State of Good Repair program award, along with $2.1 million of existing State of Good Repair funds.

The new vehicles will emit 80 percent less particulate matter, 95 percent fewer oxides of nitrogen and 88 percent fewer non-methane hydrocarbons than the older buses they will replace.