On 2 April 2014, SMRT Buses made its first ever purchase of double-decker buses and selected Alexander-Dennis to supply 201 units of Enviro500 MMC. Officially named Trident E500 Turbo, this generation of tri-axle double decker model is also known as Enviro500 MMC (Major Model Change), Enviro500NG or E50D. One initial unit was built in the United Kingdom, while the rest were assembled in Zhuhai, China. The production chassis supplied for SMRT Buses were built by Sime Darby TMA in Pasir Gudang, Malaysia. SMRT double-decker buses made their debut on BSEP Route 972 on 13 July 2014, marking a new chapter in SMRT Buses' history. Non-BSEP Enviro500 MMC units were registered SMB5001A to SMB5085H.

With the exception of its interior specifications and Mobitec EDS, SMRT Buses' Enviro500 MMC 12m double-decker buses are mechanically similar to its Hong Kong counterparts - they are powered by the Cummins ISL8.9e5340B engine (8849cc) which is Euro V compliant and fitted with ZF EcoLife 6AP1700B 6-speed automatic transmission. Air-conditioning was supplied by Denso.

This New Generation model is an evolution of the original Transbus/Alexander-Dennis Enviro500, which in turn was the direct successor to the Dennis Trident 3 which SBS Transit operates a small fleet. The Enviro500 MMC, Enviro500 and Dennis Trident are very popular models for major public bus operators in Hong Kong.

A 3-door 13m prototype was constructed for LTA as its concept bus entry, however it has not manifested as a fully functional demonstrator.