Bus Retrofit technology has been supported through a range of schemes since 2013, including a series of pilot schemes over 2013-2015 which considered a range of technologies including Selective Catalytic Reduction. Government has funded the retrofit of around 6,000 buses across England. The Department does not hold funding information in the form requested. Government has provided £64 million via the 2017-2019 Clean Bus Technology Fund and further funding has been provided for specific retrofit initiatives under the NO2 Programme (2017-present).