Alexander Dennis Enviro500

The Alexander Dennis Enviro500 (previously known as the TransBus Enviro500) is a tri-axle double-decker bus built by Alexander Dennis (formerly by TransBus) in the United Kingdom. It was unveiled in 2002 and is one of the Enviro-series bus models made by TransBus/Alexander Dennis.

Original design
The Dennis chassis for Enviro500 (also known as Trident E500 ) was modified from Trident 3. It can be fitted with Cummins ISMe335 Euro III engine (later Cummins ISLe340 Euro IV/Euro V engine which uses AdBlue to reduce emission of nitrogen oxides through selective catalytic reduction process), or ISM-330 engine for the buses delivered to North America, and coupled to Voith DIWA864.3E 4-speed or ZF 5HP602 5-speed gearbox. Later Voith DIWA864.5 4-speed gearbox, ZF 6HP602 6-speed gearbox and Allison B500R 6-speed gearbox became available and now they are the standard configurations.

Initially only the 12-metre (40 ft)-long version of the Enviro500 was built, but in 2007 Alexander Dennis announced the production of the 12.8-metre-long version, and an 11.3-metre-long variant followed in 2008.

Later Alexander Dennis developed the hybrid electric version of Enviro500, known as the Enviro500H, with GM-Allison's parallel hybrid drive system; it was unveiled in late 2008.

The body of the Enviro500 was based on the original style of the single-deck Enviro300, and the upper-deck frontal design was similar to the design used on the Plaxton President body.

The vehicle exceeded some design limitations in Hong Kong, prompting the local Transport Department to make some exclusions in order to make the buses available to KMB on time.
 * The width of the bus is 2550 mm (100.3 inches), exceeded the limit of 2500 mm (98.4 inches). The width of 2550 mm, approved by the EU, became the current standard.
 * A fixed glass replaced the emergency door at the rear of the upper deck, but with more hammers available for emergency.
 * The front indicators are the smallest of all current models of KMB.

The facelifted version of Enviro500 body, first built in late 2003, have revised frontal and rear designs. This version of Enviro500 bodywork ws also available with Volvo B9TL chassis.

In 2011, Alexander Dennis unveiled the Enviro500 with new frontal design, which had the same front with the Enviro400.

Singapore
Arriva Tampines had bought only 10 Enviro500s in 2010, and subsequently additional 32 were ordered for use on route 67 which replaces bendy buses on 10 December 2011.

The new Enviro500NG will be delivered on 22 June 2013 and these might mean additional 50 bulk orders will be delivered.