The Federal Alternative Fuels Tax Credit has been restored back to 2018 and effective through 2020. 

Icom Partners with Propane Industry and National Parks Services for low 

emmissions buses for Acadia National Park

https://www.youtube.com/watch?v=UiszZaOug5A

ICOM Propane Systems Driving Buses in US National Parks and Reducing Emissions

 Marc Steppey July 31, 2019 news

https://www.prnewswire.com/news-releases/propane-vehicles-reducing-emissions-in-national-parks-during-national-park-and-recreation-month-300891729.html