Retrofit in this instance is referring to tail pipe emissions equipment. Diesel oxidation catalyst and diesel particulate filters are the most common. For more information about these technologies and other emissions control devices please visit: http://www.meca.org/diesel-retrofit/what-is-retrofit. The GaDER program started in 2004 retrofitting school buses. Only equipment verified by the US EPA or the California Air Resources Board (CARB) is used within the GaDER program. To date over 3000 school buses in Georgia have been retrofitted with emissions control equipment.
Sometimes replacing an entire school bus may be the best option for a bus that is nearing the end of its useful life or was manufactured before stringent emissions standards were in place. Replacing a bus before its scheduled time is called early bus replacement. The GaDER program has used grant funding to segway from emissions control projects to early bus replacement projects within our school bus program. Our program requires that the school bus to be replaced be a pre-2007 engine bus that is not scheduled to be replaced within the next 2 years. The bus purchased to replace the older bus must meet a 2010 or newer emissions standard. The new bus can also be an alternative fueled bus. Most common alternative fuel types for buses are CNG and propane. Also visit EPA's Early School bus Replacement site.
The two most common alternative fuels for school buses are CNG and Propane. The school bus manufacturers offer both fueling platforms in both their conventional buses, and some of their special needs buses. As most school fleets centrally fuel, those who are choosing to use alternative fuels also install fueling stations. For fleets who are not centrally fueled, public CNG stations are becoming more wide spread throughout Georgia.