Alexander Dennis Enviro500 (3 Door)

Alexander Dennis Enviro500 (3 Door)
Manufacturer Alexander Dennis Limited (ADL)
Bodywork Enviro500 3D2S
Years in operation 2021
Operators SBS Transit
SMRT Buses
Technical Data
Length 12.5 metre
Engine Mercedes-Benz OM 936 LA
Transmission Voith DIWA 864.6
Accessibility Low Floor & Wheelchair-accessible
Emission Standard Euro VI (SCR)

In April 2019, Singapore’s Land Transport Authority (LTA) procured 50 units of the Alexander Dennis Enviro500 double-deck bus, configured with three doors and two staircases for smoother boarding and alighting. These are the first Enviro500 3-door buses to be specifically designed for the right-hand-drive market.

These buses were procured under Contract PT342 (Procurement of 3-Door Euro 6 Double Deck Diesel Buses) for ~S$34 million. In total, 100 three-door diesel buses were procured, with ST Engineering Land Systems fulfilling the other half of orders with its 50 MAN A95 (Euro 6) – 3-Door buses. Both bus types were initially expected to enter revenue service in 2020 (delayed to 2021).

This is the third batch of ADL Enviro500 buses supplied for Singapore’s public bus industry. Check out the main article: Alexander Dennis Enviro500 for more background information on the bus model.

Prior to the introduction of these buses, a one-off Alexander Dennis Enviro500 (3-Door) Concept Bus was commissioned by the LTA as a static display. It was first exhibited to the public in March 2016, and later received an upgraded new air-conditioning system in 2018 for use as a permanent display, with minor amendments to the bus cabin.

Enviro500 buses in Singapore:

These 50 new Alexander Dennis Enviro500 (3 Door) Buses would join the existing operational fleet of 216 ADL Enviro500 public buses in Singapore, procured in 2 batches. They will also be the first Euro 6 Enviro500 buses in Singapore.

Design Features

According to Alexander Dennis Limited (ADL), the bus features a full-flat floor design along with three passenger doors and two staircases, one at the front and one at the rear of the vehicle, allowing commuters to move through the vehicle quickly and safely. It will also use the latest aluminium composite body technology and a host of new safety and energy-saving features.

The rearmost axle is used as the drive axle, which differs from the standard Enviro500 offering where the middle axle is the drive axle. Significant redesign work was likely involved in relocating the engine and drivetrain components to the right, accommodating the right-hand-drive, full-low-floor layout.

Alexander Dennis Enviro500 (Euro 6) – 3-Door Batch

Buses are expected to be delivered and enter service in Singapore in 2021. The 50 buses would be registered as SG6333M – SG6382X.

The first unit(s) registered for the various Public Transport Operators are:

  • SMRT Buses – SG6349T (21 Sep 2021)
  • SBS Transit – SG6338A (21 Sep 2021)
Basic Technical Specifications
Engine Mercedes-Benz OM 936 LA, 7698cc
Power/torque rating of 260 kW (354 hp) @ 1800 rpm / 1400 Nm @ 1200–1600 rpm
Emission Standard Euro VI-compliant
BlueTec® SCR diesel technology (with EGR), common-rail fuel injection system. Requires diesel exhaust fluids such as AdBlue.
Transmission Voith DIWA 864.6 gearbox, four-speed automatic
Bodywork Enviro500 3D2S Bodywork
Both chassis and bodywork built and assembled in Zhuhai, China. Shipped completely-built-up (CBU) to Singapore.
Electronic Display Sign (EDS) LECIP Electronic Display Sign
Orange LED Matrix; Mounted on Front, Left side and Rear
PIDS LECIP OBC-VISION Passenger Information Display System
LED text displays, LCD display screens, interior speakers & exterior speaker
Driver Assistance TNT Surveillance T-Guard
– Forward collision warning system (T-FA Front Alert Camera)
– Side collision warning system (Side Alert Cameras)
Anti-Fatigue system (T-DA Driver Alert Camera)
– T-SEEDS telematics system
Additional Specifications · TNT Surveillance T-APC automatic passenger counting system
· USB charging ports
· Stroller restraint system
· Ventura doors
· Vogel Industrie System 750/3 seats
Licensed Capacity Seating (Upper deck): 51 | Seating (Lower deck): 18 | Standing: TBC | Total: TBC
Not including 2 foldable seats, 2 wheelchair bays

Contract PT342 (Procurement of 3-Door Euro 6 Double Deck Diesel Buses) was published by the Land Transport Authority (LTA) on 15 May 2018, and awarded on 25 April 2019. Alexander Dennis and ST Engineering Land Systems would deliver 50 buses each, namely the ADL Enviro500 and the MAN A95 (Euro 6).

Tender specifications for the three-door double-deck bus call for one entrance and two exit doors and the rearmost exit door must be behind the rear axle. In addition, the bus has two staircases and is built with a low-floor design. Buses are also limited to a maximum length of 12.5 metres. These buses are also Euro 6 (or Euro VI)-compliant, representing the latest in emission standards which came into effect on 1 January 2018 for all new diesel vehicles registered in Singapore.

Existing LTA requirements for new buses include two wheelchair bays; a Passenger Information Display System (PIDS) comprising LED text displays, LCD display screens and interior speakers; Advanced Driver Assistance System and Anti-Fatigue system; high-definition CCTV cameras; and automatic passenger counters at entrance and exit doors of the bus.

Transition to clean energy bus fleet

The 100 three-door double-deck buses under Contract PT342 are the last pure-diesel buses to be procured for the Singapore public bus industry.

Authorities announced during the Committee of Supply Debate 2019 that Singapore would commit to a 100% clean energy bus fleet by 2040. This commitment was further reaffirmed in the Committee of Supply Debate 2020 held in March, where it was announced that only electric or hybrid buses would henceforth be procured in line with this clean energy goal.

Design Features & Challenges

Prior to this tender, European bus manufacturers typically made fully-low-floor chassis targeted at their domestic left-hand-drive (LHD)-dominant market. As a result, drivetrain components are offset to the left of the chassis to accommodate a full-low-floor design and an optional third door at the rear. Given that the tender called for a right-hand-drive (RHD), full-low-floor diesel bus with a third door at the rear overhang, bus manufacturers faced the challenge of modifying existing designs to fulfil this (relatively) small batch of buses in the most economical way.

Alexander Dennis Limited (ADL) had relocated the engine and drivetrain components of the Enviro500 (3-door) buses to the right rear of the chassis, likely requiring significant engineering effort. This new powertrain layout allows for a full-low-floor right-hand-drive bus, the first of its kind for ADL.

ADL had previously delivered 3-door Enviro500 units in left-hand drive (LHD) specification to Transports publics de la région lausannoise (TL) and PostAuto in Switzerland; and to Berliner Verkehrsbetriebe (BVG) in Berlin, Germany. While Enviro500 buses typically feature Cummins engines, the BVG units are fitted with the Mercedes-Benz OM936 engine from Daimler. The 3-door Enviro500 buses for the Singapore market also feature the same Mercedes-Benz engine, which is identical to that in the Mercedes-Benz Citaro hybrid.

It is understood that the ADL Enviro500 (3 Door) has opted for a transverse engine layout, similar to that of the Volvo B9TL. The rear axle is now the drive axle, instead of the middle axle. This was previously identified in the concept renders released by ADL shortly after the announcement of the tender result in 2019, and since confirmed to be so, based on pictures of the actual bus. In addition, passive steering was also implemented on the middle axle to decrease tire wear and improve low-speed manoeuvrability, similar to that used on the Volvo Olympian.

Assembly in China

The 3 door ADL Enviro500 buses are built in Zhuhai (China), by a collaboration between Alexander Dennis Limited and Zhuhai Guangtong Vehicle Manufacture Co., Ltd.

ADL had partnered with the Zhuhai-based manufacturer since 2011 for bus bodywork manufacturing and assembly, supplying completely-built-up ADL buses to the Asia Pacific region. The largest market for these buses is in nearby Hong Kong, where thousands of ADL buses are operated on public bus routes. In 2019, this partnership was expanded to include chassis manufacturing and assembly, thus unifying most manufacturing and assembly work in Zhuhai.

The 11th character of the VIN number is a plant code, used to indicate the manufacturing facility at which the bus’ chassis was built. On ADL Enviro500 (3-door) buses, the digit is ‘C‘, presumably indicating China. Most 12m Enviro500 buses in Singapore mostly have ‘M‘ for Malaysia, a legacy of ADL’s former chassis manufacturing operations in Pasir Gudang, Malaysia (in partnership with Sime Darby TMA Sdn Bhd). SMB5001A and SMB5002Y carry ‘G‘ for Guildford (UK), where ADL’s chassis manufacturing operations were formerly based. All these Enviro500 buses (barring SMB5001A) were assembled in Zhuhai.

Pre-delivery visit to Hong Kong and UK

On 30 April 2021, one pre-delivery unit was showcased to franchised bus operators in Hong Kong. The bus visited Kowloon Motor Bus’ Lai Chi Kok Depot in the morning, followed by New World First Bus’ Chong Fu Road Depot in the afternoon.

According to a Facebook post by 852 SGPB, the bus was driven to Kwai Chung Container Terminal 9 after the day’s visit to Hong Kong, and was scheduled to depart Hong Kong on 3 May 2021.

In addition, one bus was spotted in UK, according to a Facebook post that sighted it along the M6 motorway (near Stafford).

Delivery to Singapore


The 50 buses are leased to the following operators:

  • SBS Transit
    SG6338A (Registered on 21 Sep 2021)
    SG6344G SG6347Z (Registered on 8 Oct 2021)
  • SMRT Buses
    (Registered on 21 Sep 2021)
    SG6345D SG6350M (Registered on 8 Oct 2021)


Concept Renders:

See Also:
External Links & References:

29 thoughts on “Alexander Dennis Enviro500 (3 Door)

  • 18 October 2021 at 2:29 PM

    Today 18th October 2021) onwards is the very first day of SMRT Buses’ 3Doors ADLE500MMC buses debuting on Express 868E (SG6349T) !!!


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