This chart depicts the number of transit buses in use in the United States, categorized by fuel type, from 2007 to 2021. In all years shown, diesel buses represent the largest portion of total buses, with natural gas buses a distant second. Hybrid buses are the fastest growing category as they have increased more than eight times from 2007 to 2021. The increase in both natural gas and hybrid buses is largely a result of favorable economics and clean air benefits in the transit bus application. Between 2020 and 2021, the total number of buses decreased. Diesel buses had the largest change with an increase of 7%. Natural gas buses had the largest decrease by 4%.

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