The Milwaukee County Transit system just got a little bit greener.

MCTS announced today that the first of 55 new Xcelsior clean-diesel buses has arrived and will be on display tomorrow, June 12, at noon at the Milwaukee County Courthouse, 901 N. 10th St.

The 55 new buses join 180 clean diesel vehicles purchased between 2010 and 2012 to total 235 clean buses in a 420-bus fleet.

The Xcelsier emits 80 percent less particulate matter, 95 percent less oxides of nitrogen and 88 percent less non-methane hydrocarbons than the older buses it replaces.

The buses also get a new design that will include an additional electronic route number sign at the rear of the bus, an added operator shield, improved accessibility with a wider doorway and a roomier interior.

MCTS usually replaces buses every 12 years or when the vehicle has reached more than 500,000 miles.