Test Drive: Wrightbus StreetDeck

Wrightbus’ integral StreetDeck double-decker was one of the stars of the show at Euro Bus Expo and includes a variety of design aspects that will please staff and passengers. Tim Deakin is the first journalist to put one through its paces in this exclusive Test Drive.

Wrightbus has long been a major player in the UK bus market, but its entry into the complete vehicle sector is more recent. At Euro 6, the Ballymena manufacturer’s integral double-deck offering is the Daimler-engined StreetDeck, which Wrightbus describes as a class leader in many ways.

Product Director Geoff Potter explains that keeping StreetDeck in this position will be an ongoing programme as more technologies become available to cut fuel consumption. Early StreetDecks include elements of Wrightbus’ Micro Hybrid system, which recaptures kinetic energy during braking to power electrical auxiliaries; full Micro Hybrid functionality is coming soon.

Geoff also promises that Wrightbus will continue its work to improve StreetDeck’s fuel economy and reduce its environmental impact.

So far the manufacturer has placed six StreetDeck demonstrators with operators. Of these, two are with First in the north of England: One at Oldham depot and the other at Olive Grove in Sheffield.

First UK Bus (North Region) Head of External Relations Brandon Jones kindly arranged for the South Yorkshire-based StreetDeck to be made available for a routeone Test Drive.

 

Build

StreetDeck is one of two integral double-deckers at Euro 6 to use Daimler’s all-new OM 934 engine, which has been designed specifically for Euro 6. It displaces 5.1 litres and produces 231bhp.

Twin turbos are fitted to ensure responsiveness. A small turbo spools up quickly to give strong power delivery from the beginning of the torque peak at 1,200rpm, while a large turbo takes over as revs increase, which they do rapidly.

Daimler gives a B10 figure – the expected life of an engine before 10% of all OM 934s will require major repair, overhaul or replacement – of 750,000km, suggesting that it is confident of the small unit’s durability.

Wrightbus’ double-decker differs from its competitors in how the engine is mounted. The short, four-cylinder unit is in-line, and drives directly via the gearbox into the differential without an angle drive.

The lack of an angle drive reduces fuel consumption by around 3-4%, but also gives significant benefits from an engineering point of view. Both sides of the power unit can be accessed easily, although the gearbox is not as easily reached as it would be in a transverse layout.

Wrightbus points out that this configuration is beneficial as engines need more scheduled maintenance than transmissions, although should the gearbox need to be removed it can be with the engine in situ. The gearbox dipstick is reached via the nearside engine bay door.

The in-line layout gives a great deal of space within the engine bay. The exhaust unit for the OM 934 is not huge, and it sits low to the offside, where the gearbox would otherwise be. The whole driveline is mounted on a removable skid.

Wrightbus has split the main radiator and the intercooler pack, with the former to the offside and the latter to the nearside with separate fans. Both are at the top of the engine bay, and air flow through each is completely unencumbered, which should remove any worries of excess heat generation.

Indeed, the radiator layout is possibly the best yet seen on a bus with a rear-mounted cooling pack; it is high enough not to attract road dirt and receives an excellent flow of air.

StreetDeck includes Voith’s four-speed D854.6 gearbox as standard, as present in both First demonstrators. ZF’s six-speed EcoLife is also available, and the promised Daimler G90 six-speed automated manual transmission remains in the pipeline, says Geoff. As tested, the bus weighs in at 10,709kg unladen.

StreetDeck is well thought out and has proved very popular at Olive Grove
StreetDeck is well thought out and has proved very popular at Olive Grove

 

Passenger access

StreetDeck has a standard entrance complete with manually-operated wheelchair ramp, and the step-free gangway continues as far as immediately behind the rear axle, although a number of seat pairs are on platforms before this point.

First has specified extensive buggy and wheelchair provision. Immediately behind the staircase is an area with three tip-up seats, split by a handrail between the second and third. That gives a buggy area, with an accompanying adult able to sit in the third position. First stipulates that tip-up seats do not return to upright on their own. To the nearside, four more tip-ups are present, split into two pairs. The front area is set up to accommodate a wheelchair user, while the rear section can fit another buggy, meaning that to First’s specification StreetDeck can carry two unfolded buggies and one wheelchair at the same time.

Naturally that impacts on the number of seats downstairs, and including the seven tip-ups there are 28. More would be possible, depending on the customer’s requirements.

A further 45 seats are upstairs, and this StreetDeck can accommodate 100 passengers in total, including a wheelchair user, at crush load; the maximum number of standees possible, when tip-ups are not used, is a cosy 34.

The staircase is easily negotiated and, on the Sheffield bus, includes glazed outer panels. These may be deleted if required by the operator, but from a passenger’s point of view the additional glazing is very welcome.

Not only does it brighten the staircase but is also admits a great deal of extra natural light to the area around the ‘pulpit’ on the upper deck and around the bottom of the staircase downstairs. Wrightbus has also fitted individual wall-mounted lights adjacent to each step, which illuminate when the saloon lighting is switched on.

Numerous handrails are present. First specifies that they are finished in purple, contrasting well with the remainder of the interior’s pastel colours. A large number of bell pushes are present: nine on the lower deck, eight upstairs.

Standard entrance with easy wheelchair access
Standard entrance with easy wheelchair access

 

Passenger comfort

Among First’s other requirements are Esteban Civic V3 seats as standard, finished in grey E-Leather. They create a high-quality impression and are comfortable. Legroom is good, including at the front upstairs – not always the case on some earlier Wrightbus double-deck bodies.

A single heater unit for both saloons is fitted, below the upper deck rear bench seat.

First’s set-up has a pre-programmed desired temperature of 21oc, and warm air vents through ceiling coving panels. The upper deck can also be fed with ambient air through vents on one side, but the lower deck cannot.

There are four opening windows in each saloon, with the hinged sections all of the same size.

Glazing depth differs, however, with Wrightbus’ aim being reduced solar gain upstairs; the 60cm window depth here, against 90cm in the lower deck, also allows thinner glass to be used, contributing to weight savings.

Headroom in both saloons is good, and someone who is around 6ft tall can stand without stooping in either. Downstairs is more airy than upstairs thanks to the taller windows and glazed staircase, although the upper deck is by no means gloomy. An internal and external CCTV system by 21st Century Technology is fitted.

First specified a high quality interior, which is pleasant to travel in
First specified a high quality interior, which is pleasant to travel in

 

Driver comfort

The instrument binnacle is shared with the StreetLite and is a simple installation, including several switches, although door buttons have been moved to below the signalling window. The steering wheel and binnacle adjust as one unit via a button activated by the driver’s left foot. Controls for the cab heating and ventilation are above the driver and to the right, adjacent to the top of the signalling window. Buttons for saloon lighting are also here.

One stalk is present on the steering column, controlling windscreen wash and wipers, horn, and indicators. Importantly, the indicator repeater tone is muted, and while detectable it is not intrusive. First specifies a full-width anti-assault screen which completely encloses the cab, and the section in the cab door cannot be lowered. The driver’s compartment is not huge, and Wrightbus is understood to be looking into moving the rear wall backwards slightly to improve this.

Visibility is very good, helped particularly by Wrightbus removing what was the B pillar on earlier double-deck bodies. The A pillar is well in front of the driver, and this revised glazing arrangement gives an excellent view to the offside. The expansive windscreen also helps visibility; nearside vision is not as good thanks to the anti-assault screen, but is perfectly acceptable.

The cab is equipped with its own matrix for heating and demisting, and feeding hot water to this is prioritised over the saloon heaters until the engine is at operational temperature. The heater unit is substantial and easily accessible by lowering the external dash panel. Windscreen washer fluid is also added here.

Cab very similar to StreetLite
Cab very similar to StreetLite

 

Performance

That Euro 6’s small, four-cylinder engines around the five-litre mark are man enough for use in double-deckers has been well established in earlier routeone Test or First Drives. They deliver multiple benefits: reduced unladen weight and fuel consumption, and improved space within the engine bay for engineering staff to work in.

Daimler’s OM 934 engine fitted to the StreetDeck works very well in conjunction with the Voith DIWA.6 four-speed gearbox, which selects neutral at stationary.

Shift quality is excellent, although when moving away from stationary with the handbrake applied it pays to depress the accelerator slightly before releasing the brake. Doing so gives the Voith a split second to re-engage drive and begin to take up power smoothly while the bus is stationary.

A small dash indicator allows engine speed to be monitored. Under full throttle the OM 934 is kept spinning between around 1,200-1,800rpm, although under part load that figure is often lower. Equally, the Voith is quick to drop a gear if necessary if keeping the engine speed up is judged to be desirable.

The Daimler unit is refined, with low noise levels, and thanks to the twin-turbo set-up is happy to pull hard from 1,200rpm. This was demonstrated when climbing Manchester Road in Sheffield, a prolonged ascent of around a third of a mile.

The StreetDeck was deliberately halted at a bus stop at the bottom of the hill, and while empty it proved easily capable of reaching 30mph from stationary despite a constant climb, and would have exceeded the speed limit if allowed to. Top gear is not selected until around 30mph under such circumstances.

First has purposely allocated the Sheffield bus to service 51 in the city. It uses this section of Manchester Road and has long been considered a testing ground by First South Yorkshire and its predecessors for new bus types, and so the StreetDeck’s fuel return should be considered with the route’s topography in mind. One member of staff who has driven the bus in service on route 51 says that it remains perfectly capable on testing hills when fully loaded.

Ride quality is very good, as it needs to be on Sheffield’s awful road surfaces. No rattles are evident, and the passenger experience on the upper deck in particular is excellent. Noise levels here are exceptionally low.

 

Verdict

Competition in the double-deck sector is keen, and all the manufacturers so far active in this area of the market offer highly competent vehicles. StreetDeck is definitely among them, and it includes the clever design aspects that Wrightbus has become renowned for, not least the glass-panelled staircase and well-executed removal of a pillar from the offside cab glazing.

First’s high-quality interior adds to the effect, but nevertheless StreetDeck is also a highly refined vehicle in which to travel. Low noise levels, good natural light and a smooth ride make sure of this, and its 100-passenger capacity on two axles is significant.

It is perhaps the engineering aspect with which First’s team at Olive Grove is happiest, however. The StreetDeck is 18% ahead of the Euro 5 ADL Enviro400s on route 51 in terms of fuel consumption and it has recorded excellent availability, despite being deliberately allocated to one of the service’s most punishing duties.

“It has settled in exceptionally well and my staff are also very happy with accessibility,” says Olive Grove Engineering Manager Alan Barstow. “Finally, it seems that a manufacturer has produced a bus with engineers in mind. The beauty of the engine being in-line is that we can access both sides of it easily.”

So far, so good, but as already explained, Wrightbus does not expect to rest on its laurels. StreetDeck is almost a work in progress, and the manufacturer will continue to improve and innovate as fuel-saving technologies advance.

Other builders in the double-deck market will need to do the same if they are to keep up with the StreetDeck. It has taken time to come to market, but on this showing has been well worth the wait.

 

Wrightbus facts