CHICAGO (CBS) - The Chicago Transit Authority is taking another step in going green, with its first-ever all-electric buses.

The CTA is adding two buses with all-electric propulsion systems, paid for by a $2 million federal grant.

The standard-size 40-foot buses will not be arriving for a while. The CTA has yet to decide what brand to buy from, or announce when the pilot project for the buses will start, the Chicago Tribune reported.

Once they are purchased, the buses will first be tested to determine how they will perform in traffic, the Tribune reported.

Right now, the CTA has more than 200 hybrid buses, and more than 1,500 diesel buses, the newspaper reported.