Clean Diesel technology is being utilized by transit buses at a faster pace than other large vehicle sectors, according to the director of policy for the Diesel Technology Forum Ezra Finkin.

Forty-four percent of U.S. transit buses meet or exceed the EPA clean diesel standard, which is 11% higher than heavy-duty fleets that meet or exceed the standard.

Finkin noted at the American Public Transportation Association’s (APTA) Expo Bus and Maintenance Technical Session in Houston that the adoption rate from transit agencies is unexpected.

“The rate of adoption by transit agencies of clean diesel technology surprised us and is very significant, since transit agencies are at the forefront for evaluating the best fuels and technologies to serve their communities,” Finkin said.

New clean diesel buses have reduced both NOx and particulate matter emissions by 98 percent compared to 1988 buses, according to Finkin.

The APTA’s 2013 data showed the breakdown of public transit bus fleets fuel usage. Diesel buses had a significant lead compared to the rest of the fuels with 77%. CNG trailed behind with nearly 20 percent and LNG made up nearly 1%. The combined percentage for hydrogen, electric, hybrid and propane made up .5%.

Currently, 81 percent of the diesel buses in the U.S. fleet were conventional diesels, 12% were diesel-electric and 7%  operated on biodiesel, according to APTA data.