Wrightbus StreetLite Micro Hybrid

The lightweight market is increasingly where the bus industry is turning for single-deck purchases. Manufacturers have reacted accordingly, and there is a variety of models available promising long service lives and all-important good fuel efficiency.

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Wrightbus’ StreetLite Micro Hybrid was the first of the current crop of lightweight diesel buses to achieve low carbon emission bus accreditation.

What this means is that not only does the Micro Hybrid equipment – which charges the batteries during braking to power auxiliaries – deliver a significant fuel saving, it also entitles the operator to enhanced BSOG payments without the extra costs associated with a full hybrid’s complexity and batteries.

In England that’s worth an additional 6p per kilometre, and in Scotland an extra 14.4p, which when combined with reduced weight equals a significant efficiency gain. Indeed, one senior bus industry manager has commented that it may take just two years to cover the on-cost of the Micro Hybrid equipment; anything after that is ‘money in the bank’.

StreetLite has so far been purchased by four of the big groups, with the Micro Hybrid featuring heavily. Among the most recent deliveries are 15 10.7m Door-Forward examples supplied to Arriva Southern Counties. Regional Publicity Manager Richard Lewis kindly arranged for one to be made available for a routeone Test Drive.

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StreetLite is now a known quantity and is available in a variety of sizes. In door-forward configuration it has the presence of a full-size, heavy duty bus with the exception of smaller wheels.

It is constructed using Wrightbus’ patented Aluminque method, delivering high rigidity and low weight.

StreetLite is modular, giving commonality between variants, and body panels are quickly released, speeding replacement. Power comes from a 4.5-litre Cummins ISBe engine coupled to a four-speed Voith gearbox. The engine bay is well filled, and includes a Groeneveld Oilmaster system which automatically controls the engine oil level.

Engine bay full, but drivetrain and cooling system on demountable skid
Engine bay full, but drivetrain and cooling system on demountable skid

When heavy work becomes necessary the engine, gearbox, cooling system and exhaust are easily removed on a demountable skid.

Oil and coolant are added at the extreme rear offside through fillers behind a hinged flap. Also beneath the flap are the dipstick, coolant level gauge and emergency engine stop.

Oil and water added at rear offside
Oil and water added at rear offside

Diesel and AdBlue fillers are located nearby but quite low down; tank capacities are 225 and 38 litres respectively. They are adjacent to each other, which has led Wrightbus to attach an unpainted panel over the conventional panelling beneath them, preventing inevitable spills from damaging the paintwork.

From the passenger’s point of view, StreetLite is a nicely put together bus. Its window line in the low-floor section is low and straight, rising somewhat in the rear area. The saloon is airy and the roof very high.

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Access is good, with a 120cm doorway leading to an aisle which, thanks to the bus’ small wheels and associated components, is wide above the front axle.

Entrance is welcoming
Entrance is welcoming

A Hanover destination system is fitted, including side and rear repeaters.

The manual wheelchair ramp is by PSV Transport Systems and simple to operate. It includes a small handle on a bungee cord which makes opening and closing the ramp very easy; this retracts fully when not in use thus not posing a trip hazard.

Manual wheelchair includes bungee cord to open and close
Manual wheelchair includes bungee cord to open and close

A pair of side-facing seats is mounted above the offside front wheel; directly opposite is a luggage area, which may benefit from slightly better-located handrails to prevent suitcases and larger bags from falling out under heavy braking or sharp cornering.

A buggy bay is present on the offside and a wheelchair position to the nearside, both clearly marked. Each bay has three tip-up seats, which unusually don’t return upright automatically.

Five priority seats are present immediately behind the buggy and wheelchair areas, and again they are clearly marked; one sits alone on the offside. All have rotating armrests on the aisle side, unlike the remainder of the bus’ seats, and thanks to clever positioning passengers in all five priority positions can reach a bell push without needing to stand or reach backwards.

Five priority seats all have easy access to bell pushes
Five priority seats all have easy access to bell pushes

Including tip-ups and the two over-wheel positions, a credible 23 seats are in the bus’ low-floor area; the remaining 17 are reached by two steps immediately ahead of the rear axle, which are 19 and 20cm high respectively. The emergency exit is amidships.

Handrails and guards are in Arriva-standard cream, and bell pushes are numerous; there are 13 in total, including a forward-facing one in the wheelchair area – almost one for every three seats.

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The StreetLite is an urban bus, and so its interior is functional. Arriva has specified some extras to bring the standard up from Wrightbus’ baseline, but even if it had not, the saloon would still offer a pleasant travelling experience, thanks mainly to its high vaulted ceiling and large windows in the low-floor section.

Dcor is in Arriva’s corporate scheme and predictably dominated by aquamarine and cream. Seats are covered in synthetic leather and spaced well enough, with pitch varying from 70 to 75cm.

Interior is welcoming and airy, helped by Arriva dcor
Interior is welcoming and airy, helped by Arriva dcor

Heating and ventilation is by blown air from vents above the offside windows.

Fan speed is automatic, but the driver is able to set the temperature. Four opening windows are present, two on each side.

Lighting is by a central, continuous strip mounted in the apex of the ceiling and extends from front to rear, although the section above the platform sensibly illuminates only with the door open and the headlights on.

Arriva has specified Wi-Fi on these buses and they also have a nine-camera CCTV system. Three are in the saloon, one in the cab and there is a forward-facing camera on the dashboard; the remaining four are external at the rear.

Two are above the rear window and one on each side, facing forward.

Noise levels are as would be expected from a bus, but the most obvious source when moving was the rear axle, meaning that the centre of the bus is slightly noisier than the extreme rear. The small Cummins engine is refined; the Voith gearbox’s trademark whine is detectable.

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The cab is reached via two steps, and Arriva’s specification includes a full-length anti-assault screen, although the portion in the door can be raised if required and it has a large hole cut to access the ticket machine. The internal rear-view mirror is mounted on the cab side of the screen.

Little information is ordinarily given via the dash binnacle, with only an analogue speedometer and digital vehicle status visible on start-up. The binnacle is attached to the steering wheel and they move as one unit when adjusted.

The latter shows an image of the bus and makes the driver aware of any problems or circumstances they need to know about. A small digital rev counter is also present. The four buttons adjacent give access to fuel and AdBlue levels, coolant temperature and air pressure data, but the display quickly defaults to the status screen.

Several buttons are mounted on the right of the dash, including some of those related to starting the bus, as are gear selection buttons. Interior lighting switches are above the driver’s head; heater controls, the handbrake and the master switch are below the signalling window.

Cab is simple but well laid-out
Cab is simple but well laid-out

The signalling window is of reasonable size but would benefit from a wider opening. The driver is surrounded by glass, and although a fan is fitted the cab became noticeably hot on what was admittedly a warm day in Kent. Air-conditioning is the ultimate answer, but that’s a matter for operators.

Type training will make drivers aware of two audible warnings. When starting the StreetLite, a male voice loudly announces that the fire suppression system is working correctly, and when it has been idling for five minutes a tone is sounded before the engine shuts down.

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In 10.8m Door-Forward, 40-seat layout the StreetLite weighs 7,817kg unladen, significantly below comparable heavyweight buses, but thanks to its 4.5-litre Cummins engine it has a similar power-to-weight ratio.

Performance is thus little different to that of a heavyweight, but before that can be sampled the driver needs to be aware of a complex starting procedure. It entails two master switches, a steering column-mounted button and finally activating the starter motor; the switch on the steering column is initially awkward to find.

Selecting a gear is simple, requiring the brake pedal to be depressed.

An admittedly unladen hill start on a steep incline near Gillingham was tackled with ease, the bus easily achieving and holding second gear, but the most impressive part of the test came on Prince Charles Avenue in Rochester.

Here, on an incline approaching 15%, the StreetLite romped to the top, only needing to change into first gear when approaching the summit.

The gearbox’s hydraulic retarder performed equally well on the descent, holding the bus at little more than walking pace without recourse to the foundation brakes.

Gearshifts are smooth, as expected of a Voith, and the complete drivetrain – engine, gearbox and rear axle – comes with a two year or 200,000km warranty.

The tachometer allowed shift points to be observed, and demonstrated how capable small engines are at low revs. The ISBe idles at 700rpm but is happy to pull from below 900rpm, and even under full throttle lugs down to around 1,000rpm – 200rpm below peak torque – quite happily.

This adds weight to the verdict delivered in a test of Volvo’s B5TL (routeone, Test Drive, 25 June) that the new generation of small engines are man enough for the job.

The Voith gearbox tailors its shifts according to this flexibility, although one downside is that it can ‘hunt’ a little between gears in urban traffic.

That characteristic is more than made up for by excellent fuel economy returned during the test, for which the Voith must take some credit.

Top speed is limited to 56mph, and while in the congested Medway Towns it was not possible to achieve much more than 40mph, the StreetLite’s sprightliness suggests that it would easily cruise at that maximum.

Manoeuvrability is very good and the bus handled a particularly awkward rising switchback-type turn off a roundabout in Chatham easily. As with all Wrightbus products, the deep, curved windscreen gives excellent visibility, complemented by a large offside expanse of glass.

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The StreetLite Micro Hybrid is a clever vehicle. Using momentum to power auxiliaries both saves fuel and leads to an increase in BSOG payments, a win-win situation.

Although Arriva has chosen to add muted branding extolling the buses’ low carbon emission credentials, most passengers – and drivers – will be unaware of Micro Hybrid’s fitment.

Arriva promotes the bus' low carbon credentials
Arriva promotes the bus’ low carbon credentials

Its use cannot be detected, and the StreetLite drives exactly as a conventional bus would.

Add to this the bus’ 40-seat capacity packaged within a sub eight-tonne UVW and it becomes a very attractive vehicle as well. The Cummins/Voith drivetrain has long proved itself durable in other models, and the engine punches well above its modest weight. Visibility is good and the passenger environment is pleasant, helped by Arriva’s interior specification.

With a lifespan of up to 18 years promised by Wrightbus, the StreetLite looks set to match heavyweights’ longevity without incurring their purchase and running costs.

A full-weight single-decker may still be best for certain applications, but if you’re in the market for a bus around the 40-seat mark it will pay to think very carefully about the StreetLite.

TestSpec

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