• A 2019 Georgia State study found that diesel school bus fumes drive down test scores. The study correlated increased academic performance when children were exposed to lower levels of school bus emissions. Student test scores improved in both math and English.
• Diesel is a carcinogen identified by the World Health Organization. Children are more sensitive to diesel exhaust because they breathe faster.
• Compared with diesel, propane engines operate about 50 percent quieter, which increases safety and decreases driver fatigue.
• The driver’s ability to hear students and emergency vehicles while a bus is in motion is a huge safety advantage for everyone on board.
• Propane fueling is a closed-loop system. With propane, drivers and maintenance technicians avoid the frequent spills and odors that other fuels may exhibit on their clothes and hands.
• The Environmental Protection Agency classifies propane as a non-contaminant. It is a nontoxic, non-carcinogenic and non-corrosive fuel.

Knocking Out NOx

• Propane is naturally lower in nitrogen oxides (NOx) than diesel and gasoline.
• According to a monumental West Virginia University study released in 2019, propane school buses reduce NOx by at least 95 percent. In real world applications of stop-and-go bus driving, diesel emissions are 34 times higher than with propane.
• NOx are highly damaging emissions that are federally regulated due to their negative impact on human health and the environment.
• NOx can cause damage to respiratory airways and cause eye, skin and respiratory tract irritants.
• Breathing NOx can cause damage and scarring of the airways. 

• NOx contributes to numerous environmental problems such as acid rain, climate change, deteriorated water quality, ground-level ozone (smog), air toxics and particulate matter.

Reduced Particulate Matter

• School buses fueled by propane emit virtually zero particulate matter.
• According to the Lancet Commission, particulate matter is associated with increased risk of cardiovascular disease, pulmonary disease and kidney disease. It contributed to about 4.2 million premature deaths in 2015.
• With propane school buses, students, drivers and school staff aren’t exposed to the harmful particulate matter found in diesel exhaust, which is known to aggravate asthma.
• A U.S. Department of Veterans Affairs study found that the global toll of diabetes attributable to particulate matter air pollution is significant. The study states that reducing exposure to particulate matter will yield substantial health benefits.

Less Environmental Impact

• Buses fueled by propane emit fewer greenhouse gases, nitrogen oxides and total hydrocarbon emissions when compared to diesel buses.
• The ultra-low NOx propane engine is 90 percent cleaner than EPA’s current emissions standard. (ROUSH CleanTech manufactures the 0.02 g engine for the Blue Bird Vision Propane bus.)
• At 0.02g NOx, it takes 10 propane buses to emit as much NOx as one modern clean-diesel bus.