Interest in biogas-fuelled buses has grown recently thanks to Scania and ADL’s partnership to develop the Enviro400 CBG. The first are with municipal Reading Buses, and we find out how they perform
The jury remains out on where the bus industry goes post-diesel, but Reading Buses’ mind was made up a long time ago.
Gas is the answer as far as it is concerned, and earlier this year it because the world’s first operator to place a Euro 6 biogas-fuelled double-decker into service.
Reading now has five of these Scania N 280 UDs with Alexander Dennis (ADL) Enviro400 CBG bodywork on the road, and Chief Engineer John Bickerton says that it would surprise nobody at the operator if the type wins this year’s tendering round for new double-deckers.
“The biogas double-deckers have performed brilliantly so far and drivers love them, although we currently have three diesel Scania Enviro equivalents on loan and they are doing very well too.
“From the cab there is little difference between diesel and biogas examples, although in the saloon the quieter gas engine means that the gearbox noise is audible; in a diesel, it is not.”
Reading Buses already has a considerable number of biogas-fuelled single-deck Scania Enviro buses, and John says that their fuel consumption is broadly comparable with the double-deckers’, at around 2km per kilogramme of gas. Gearbox optimisation work is still to be done on the double-deckers, which should improve returns slightly.
Scania says that it is committed to biogas buses as a major component of its range at Euro 6, and it recently disclosed that requests for quotes for gas now account for 50% of operator interest.
Gas allows a simpler driveline than diesel and biogas is carbon neutral because it is produced by anaerobic digesters from food waste. The current climate makes that A Good Thing, and it would be no surprise to see the Enviro400CBG gain traction with other buyers over coming years.
John kindly made one of the Reading examples available for a routeone Test Drive.
Build
The Enviro400CBG body is very similar to the Enviro400 MMC, but it is built to an interim length of 11.46m that is not offered with diesel chassis. It is 4.32m high.
An extended length gives space at the rear of the upper deck to house gas tanks while retaining the seating capacity of the short Enviro400 MMC.
The tanks’ location is obvious; in place of the rearmost row there is a large box, and so they cost four seats. For Reading Buses capacity is key, but John says that the compromise is something that it is willing to accept. Some gas tanks are also under the staircase.
Scania’s OC09 engine is fitted. It displaces 9.3 litres and develops 280bhp; torque is produced in the same manner as a diesel, with the OC09 pulling well from 1,000rpm.
The engine is mounted on the offside, with a large radiator directly above it. As a result, like the diesel Scania Enviro400 MMC, there is no lower deck rear window.
The gas chassis’ radiator is larger than a diesel’s, and John reports that the Euro 6 single-deckers in the Reading fleet – which share the same driveline as the double-deckers – have seen no instances of cooling problems even in the warmest weather. An advantage of the gas engine’s higher operating temperature is that waste heat for the saloons is plentiful.
Alcoa Dura-Bright alloy wheels have been specified. That may sound extravagant for a bus, but John points out that research shows that their lower mass when compared to steel wheels results in a 3% fuel consumption saving – a significant amount, regardless of the fuel type used.
The Enviro400CBG body has 45 seats upstairs and 27 downstairs including tip-ups. 14 standees can be carried for a total capacity of 86. Unladen weight is a respectable 11,855kg.
Passenger access
A manual ramp is fitted that leads to a wide gangway.
All five of Reading’s Enviro400CBGs have two wheelchair spaces; each has only one tip-up seat present, reducing lower deck seating capacity by three over a bus with one wheelchair area and a buggy zone.
“It is surprisingly common for two wheelchair users to travel at the same time,” says John.
“When buses only have space for one that means that they have to split up and travel on different journeys, and that is not ideal.
“We have approached the Department for Transport about a derogation on aisle width to allow four tip-ups in the offside wheelchair bay, but the trade-off in capacity is acceptable as it creates standee space when a wheelchair user is not present.”
On the lower deck, 10 fixed plus two tip-up seats can be reached without a step and there are 13 bell pushes present. In the upper saloon there are just five bell pushes and all are on the nearside.
The bus is equipped with audio-visual internal next stop announcements, complemented by an external speaker that announces the destination when the bus is at a stop.
A Hanover destination display system is fitted, and it also includes a unit on the offside of the lower deck. White LEDs are used, rather than orange on earlier buses in the Reading fleet.
Passenger comfort
Reading goes for a high internal specification as standard and the Enviro400CBGs are no exception.
Seats are the Esteban Civic V3 type and almost all fixed examples are high backed.
Every seat has a USB charging point, and forward-facing positions have a coat hook on the back of the seat in front.
A single marble-effect table is fitted on the upper deck offside immediately behind the staircase ‘pulpit’. It has a wireless charging pad suitable for some mobile devices, while a cord with a USB adapter is fitted for users of other types.
The cord initially looks vulnerable to damage, but at John’s encouragement it was pulled as hard as possible and did not come away from the in-table securing point. If it is damaged, a replacement costs around £15.
Two heater boxes are fitted on the lower deck. One is at the rear and the other beneath the staircase, but they both also feed to the upper deck; as a result, no water is pumped upstairs.
Heaters vent through substantial grilles, including one on the upper deck that is part of the cowling over the rear gas tanks. The engine reaches operating temperature very quickly and both saloons rapidly begin to warm up.
Wood effect flooring is fitted throughout and handrails are in silver. Saloon lights have an automatic setting, where they switch on and off depending on ambient light; they can also be controlled manually.
A 16-camera CCTV system can be scrolled through by the driver on a small cab monitor and free 4G wi-fi is fitted.
Driver comfort
As with the rest of ADL’s Enviro MMC range, cab storage has been well thought out. Holders for a drink and running board are present, while there is much space around the KAB sprung seat for a bag.
A retractable anti-assault screen is present and the cab door can be locked from the inside.
The driver benefits from electric air-conditioning while the wipers’ upper parking position means that they are well away from even the tallest driver’s line of sight.
Visibility to both sides is good and the large mirrors are helpful. In Reading’s experience, the one on the nearside is vulnerable to damage, however.
Scania’s standard dash is fitted and it provides all the information that the driver needs. The steering wheel adjusts via a button on the column and the driving position is very good; the stalk arrangement is also good and the handbrake is easily within reach.
Performance
The bus performs well, with the OC09 engine having enough power for the job. It is not spectacularly fast, however, and the EcoLife gearbox changes up as early as it would in a comparable diesel in the name of fuel economy.
It also takes engine speed past 1,500rpm if judged necessary and, as ever, shift quality is excellent. The integral gearbox retarder also works well and it complements brakes that feel solid despite the small pedal.
Two things quickly become noticeable when driving the Enviro400 CBG for the first time. One is that its wheelbase is substantial, and care must be taken in urban centres as a result.
The other is how quiet it is. Scania diesel engines are muted, but the OC09 is even more so, and this perhaps influences the impression of how quickly speed is gained.
Chassis handling is good and the steering lock is tight, benefiting manoeuvrability despite the long wheelbase.
Verdict
Scania’s hopes for its biogas double-decker are well known. When combined with a fuel supply package from partners the Gas Bus Alliance or Roadgas that also includes depot infrastructure, it says that the Enviro400 CBG stacks up from a purely commercial viewpoint.
Importantly, the model also performs well both when driven and from an operator’s point of view.
“We are absolutely happy with the biogas double-deckers and we would take more tomorrow if we could,” says John. “On our single-deckers we change the spark plugs every year, but at £60 for a pack of six, it is a modest expense.
“Drivers also like gas buses and they have proven reliable.
“I would like ADL to remove the remaining vertical handrails on the upper deck in favour of seat-mounted handles because if they are not there then they can’t rattle, but other than that it has accommodated what we asked for.”
The only area where the Enviro400 CBG loses out to diesel variants is in capacity. The rear gas tanks cost four seats, but John says that this is a price that Reading is willing to pay for a vehicle that delivers exceptional reliability.
Apart from that, all of the positive points of ADL’s MMC range are present in the biogas double-decker and to Reading’s specification it is a highly attractive vehicle in which to travel. That offering will only get better when ADL introduces individual passenger service units.
Scania’s chassis contribution to the overall package is also impressive. It complements the passenger experience through low noise levels and a smooth ride, and on this showing the Swedish manufacture’s confidence in its alternative fuel range is well justified.
