[4][5] A common design was used primarily that the bus has a single-curvature windscreen with a peaked roof dome and a separately mounted destination sign.

The bus was developed to compete with the European-built heavy-weight single-decker buses sold in the United Kingdom, the most notable being Volvo.

Many full-size (12 m (39 ft) or more) single-decker buses are primarily designed for use on the continent and to carry a large number of standing passengers which is commonplace on the continent, but the Enviro300 was designed solely for the UK market where large numbers of standing passengers are not often carried.

The Enviro300 chassis was also able to be fitted with bodywork by other manufacturers, with Courtney Coaches purchasing East Lancs Esteem bodied examples in 2006.

[8] In late 2007 Alexander Dennis introduced a second generation version of Enviro300 which featured styling cues similar to the Enviro200 Dart and the Enviro400.

It had a single-piece windscreen covering the destination display (no longer a peaked roof dome similar to the Marshall Capital and the MCV Stirling).

Capable of a range of 300 kilometres (190 mi) at maximum capacity, the 'Bio-Bus' was initially loaned to the Bath Bus Company, requiring the installation of a temporary fuelling station at the Bristol Sewage Treatment Works in Avonmouth, before commencing on demonstration duties across the United Kingdom.

[37] A hybrid electric derivative of the integral Enviro300 named the Enviro350H, equipped with BAE Systems hybrid technology used in the Alexander Dennis Enviro400H, was launched by Alexander Dennis in 2010, initially available with Tata Hispano bodywork exclusively for the Continental Europe export market.