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World premiere Mercedes-Benz CapaCity L: Even longer and more spacious, even more efficient and safe: the new large-capacity Mercedes-Benz CapaCity L articulated bus measures up on all fronts
- Space for 191 passengers over a length of 21 m
- A giant on wheels with a concept that is made to measure
- Amazingly manoeuvrable, despite its length
- Handling and safety at a new level for large-capacity buses
- Unique anti-jackknifing system ATC (Articulation Turntable Controller) in the CapaCity L
- Powerful and extremely efficient: the engine of the CapaCity L
- Inner values: the interior of the CapaCity L
Stuttgart / Mannheim - Truly a big deal: in its standard version, the new Mercedes-Benz CapaCity L can accommodate up to 191 passengers. Developed for exceptionally busy routes in congested urban areas, this large-capacity articulated bus is great in many respects. It offers great manoeuvrability, for despite its exceptional length of 21 m the CapaCity L is amazingly agile. And the new CapaCity L is great in extreme driving situations, too: with its new Articulation Turntable Controller (ATC) and its ingeniously steered fourth axle, it sets the benchmark for safety and handling. It demonstrates great economy, too, thanks to the low costs involved: the CapaCity L is based on the modular system of the best-selling Mercedes-Benz Citaro, so reducing procurement as well as upkeep costs. Its efficient drive system ensures that fuel consumption and emissions are kept low: no other diesel-powered urban bus uses less fuel per passenger space.
Growing demand for large-capacity urban regular-service buses
Sometimes, 'big' just isn't big enough, and at that point even the capacity of the spacious 18.1 metre-long articulated Mercedes-Benz Citaro G is overstretched. This is particularly true in the case of busy city bus routes during the rush hour and of specialised BRT systems (Bus Rapid Transit) using dedicated lanes.
Transport operators in major cities and conurbations are all registering an increase in passenger numbers. While on the one hand this relieves the situation on city streets, on the other hand the existing transport systems are stretched almost beyond their limits. In some cases the capacity of the available buses is no longer sufficient, but there is no possibility of adding services to the timetable as this would only cause a backlog of buses at stops and traffic lights. The answer to this problem is the Mercedes-Benz CapaCity L, which represents part of the solution to inner-city traffic problems.
From the Mercedes-Benz CapaCity to the new CapaCity L
Where there is a demand for high passenger capacity, for seven years now the proven Mercedes-Benz CapaCity in its Euro V version has been the first choice for customers in Europe. This four-axle large-capacity articulated bus has in many respects set the benchmark: some 350 CapaCity models are in use in a dozen or so cities between Istanbul in Turkey and the north of Germany, making it the most successful large-capacity bus in Europe.
At the instigation of the transport operators its successor, the new Mercedes-Benz CapaCity L, has grown further: at a length of precisely 20,995 mm, the new Mercedes-Benz CapaCity L is some 1.5 m longer than its predecessor and 2.9 m longer than a Citaro G. This makes the new CapaCity L the longest urban regular-service bus in Europe with a single articulation joint. The standard version of the new CapaCity L can accommodate up to 191 passengers, as compared with 186 passengers in the CapaCity Euro V and 163 in the recently launched Citaro G articulated bus with OM936h engine.
A giant on wheels with a concept that is made to measure
Sheer size and a large capacity alone, however, are not enough for a highly specialised large-capacity bus concept. Dimensions, axle configuration, steering, drive unit, the arrangement of the doors and the design of the passenger compartment for such a giant on wheels all need to be factored into the equation. The issues here are manoeuvrability and driveability, practicality and safety on the road and, not least, economy.
The demands in terms of manoeuvrability are obvious. But other essential factors include details such as the angle of approach/departure between the front and rear sections - important, for example, when driving through areas with traffic calming measures such as road humps. Further factors of particular importance to operators include ease of maintenance and repair and fuel-efficient engines, through to the necessary traction and safety in critical road conditions.
Not least in view of the purchase price, reliability in demanding regular-service operations is a key factor, including the availability of spare parts and thus close links to the volume production facility.
The new Mercedes-Benz CapaCity L brings all these elements together in a single coherent whole that is based, both visually and technically speaking, on the platform of the best-selling Citaro G, already proven many thousand times over. The drive system, including the arrangement of the various assemblies, is derived from the same source, so ensuring exceptional ease of maintenance and repair. The use of a single articulation joint contributes to this - a significant cost factor considering the quite customary service life of ten years or more. Last, but not least, drivers of the CapaCity have little need to readjust: the cockpit is identical to that of the established Citaro, while the CapaCity L is very nearly as nimble as the Citaro G. Manoeuvring and reversing are just as easy as with any other bus with a single articulation joint.
Large-capacity bus built on the modular system
A glance at the technical data underlines the close relationship between the new CapaCity L and the Citaro G: the front section back as far as the centre axle is identical, as can be seen from the dimensions for the wheelbase and the front overhang. The rear overhang, too, corresponds to that of the familiar urban bus.
Where the CapaCity L differs from the Citaro G articulated bus is primarily in the additional segment added at the back of the front section, as well as in the significantly extended front part of the rear section with an additional, fourth, axle. This ensures a harmonious distribution of weight. These additions also explain the longer length compared with the previous model. The extra length comes mainly from the additional segment of 610 mm inserted behind the second axle of the front section, together with a second segment (660 mm) in front of the drive axle in the rear section.
The framework structure of the CapaCity L is also based in principle on that of the Citaro. Whether we are talking about the proven annular frame technology employed here, or about the so-called sword-hilt elements used where the framework elements intersect - the CapaCity L derives from the modular system. The supporting structure has been reinforced just enough to compensate for the higher loads incurred through the extra length, the fourth axle and the permissible GVW of 32 t of the CapaCity L as compared with 28 t for the Citaro G.
During the development phase, the engineers were able to leverage the positive experience gained over many years with the first generation of the CapaCity. Deployments for this model include 250 units operating on the well-known Metrobus line in Istanbul; indeed, it represents the backbone of that city's public transport system. The line is used on a daily basis by some 800,000 passengers - a real endurance test that the CapaCity has passed with flying colours.
Individual design options
It is also clear from the design of the new CapaCity L that it is a direct offshoot of the best-selling Citaro urban bus family. This large-capacity bus offers a friendly welcome to passengers as they board. Wide expanses of glass make the vehicle appear inviting, light and airy, despite its imposing dimensions. Its contoured wheel arches and the sweep of its side windows give the CapaCity L a modern and at the same time dynamic appearance.
As an alternative to the standard design, the new CapaCity L, like its predecessor, is also offered with the option of individualised styling. The Metro design package includes side panelling to conceal the bus's various roof structures, such as the air conditioning system.
The Tram design package comprises roof panelling along the full length of the vehicle, including above the bellow of the articulation joint. In addition, the bellow is available in a range of different colours and translucent materials.
As is already the case with the Citaro, the CapaCity L can also be fitted as an option with a smooth front-end flap, with visually enhanced rear light clusters or with concealing panels over the non-steered wheels. All these elements can be individually combined with one another, resulting in a great variety of models.
Amazingly manoeuvrable, despite its length
Thanks to a maximum wheel angle of 42 degrees on the front inner wheel in bends and its steered fourth axle, the new CapaCity L is manoeuvrable within the regulations set by the German road traffic licensing authorities and the turning ability defined therein, despite its considerable overall length.
The turning circle of the CapaCity L is 24.47 m, while the minimum turning track within the turning circle is 7.1 m. Despite a length of 21 m, the CapaCity L therefore does not require any special exemption in relation to its turning circle. Nor is its use on certain defined routes restricted.
The only exemption needed in the case of the large-capacity bus relates - as in the case of its predecessor - to its exceptional length, given that the new CapaCity L, with an overall length of 21 m, clearly exceeds the legally permissible maximum length of 18.75 m for vehicle combinations.
Handling and safety at a new level for large-capacity buses
Manoeuvrability and handling are crucially important factors for a large-capacity bus. The CapaCity L sets a new benchmark for these criteria. A distinctive feature of the large-capacity bus is its fourth axle, which first of all provides the basis for the increased permissible gross vehicle weight of 32 t (Citaro G: 28 t) and an evenly balanced distribution of weight. At the same time, the steered fourth axle is what gives the CapaCity L such outstanding cornering ability.
The new steered trailing axle differs from the version used on the previous model in that it features individual wheel suspension. It has already proved itself as the trailing axle used in touring coaches such as the Mercedes-Benz Travego M and Travego L. The trailing axle combines exceptional suspension comfort with superb handling and low tyre wear. Added to which, it also contributes not least of all to the low fuel consumption of the CapaCity L. The CapaCity L is available as an option with a roll/pitch control system. This electronic system improves the vehicle's stability further by automatically adjusting the shock absorber characteristics according to the driving situation and vehicle load.
Actuation by ASA optimises manoeuvrability
Actuation of the electro-hydraulic steering of the fourth axle is undertaken by the ASA system (Additional Steering Axle). The system's control unit uses numerous parameters to calculate the required steering angle for the trailing axle. These include the articulation angle of the joint, the turning angle of the front axle and the speed of the bus as well as numerous other key variables. If the actual steering angle differs from the required angle, the servo cylinder will automatically steer the fourth axle in the necessary direction.
At driving speeds of over 40 km/h the steering of the trailing axle is automatically centred. This improves further the straight-line stability and thus the handling of the CapaCity L at higher speeds. The centring process takes place gradually and is imperceptible to the driver.
Among the major advantages of the CapaCity L in comparison with other large-capacity bus concepts is its unrestricted capability for manoeuvring during reversing. As when driving forwards at low speeds, here too the fourth axle is actively steered. The steering angle is controlled by the articulation angle of the joint.
Excellent turning circle, turning track and swing-out values
The good cornering ability of the new CapaCity L is the outcome of a lot of detailed calculation work as well as extensive on-the-road tests. This has resulted in an impressively tight turning circle, given the length of the CapaCity L, of 24.47 m.
On top of this comes a minimal turning track of just 7.10 m (previously 7.48 m). The turning track is the term used to describe the minimum width of road that a vehicle needs for its movement when turning or turning round - in practice, this figure is just as important as the turning circle.
Furthermore, compared with the predecessor model, the swing-out value has been reduced to 1.49 m (previously 1.64 m). This figure defines how far the rear end swings out when the steering wheel is turned to its full extent.
The ingenious steering system for the fourth axle also reduces the extent to which the rear end swings out when leaving a bus stop: in this situation the steering system for the fourth axle reacts by applying a pre-defined delay to the steering angle of the front axle. This clever concept means that, when pulling away from the bus stop, the trailing axle will have moved away from the kerb even before the first full turn of the steering wheel. If necessary – for example when the steering wheel is turned fully immediately upon pulling away - the driver can also press a button to centre the steering of the trailing axle ("bus stop function"). In both cases the wheel is prevented from touching the kerb and the rear end from swinging out over the pavement at the bus stop.
Further advantages of the CapaCity L include the harmonious distribution of weight as a result of the combination of rear-mounted engine and twin axle in the rear section. At the same time this ensures exceptional handling as well as excellent traction. The latter can be improved further if necessary by taking the weight briefly off the trailing axle, thus automatically increasing the load on the drive axle.
Unique anti-jackknifing system ATC (Articulation Turntable Controller) in the CapaCity L
One of the key features of the CapaCity L large-capacity bus is its articulation joint. This is a standardised joint platform employed all over the world, which is also used in the Citaro G. The maximum articulation angle in both cases with the steering wheel fully turned is 54.5 degrees.
Another ingenious feature is the unique ATC system (Articulated Turntable Controller) on the CapaCity L, newly developed by Mercedes-Benz. ATC sets a new standard for handling and safety in articulated buses: the ATC dynamic control system works quickly and above all to the precise extent needed to regulate the hydraulic damping of the joint as a function of factors such as the steering angle, articulation angle, speed and load. To achieve this, the ATC relies on the data from the CAN databus.
The effect: whereas elsewhere the customary high basic level of damping of the joint can lead to a distinct tendency to understeer in bends and to increased tyre wear on the front axle, the joint of the CapaCity L runs virtually free during normal, stable, operating conditions and is dampened purely by the friction between the elements. This optimises turn-in ability and steering effort, with the result that the steering forces and responsiveness of the articulated bus are virtually on a par with those of a rigid vehicle. The reduced tendency to understeer minimises tyre wear on the front axle.
Should the vehicle find itself in an unstable situation - for example in slippery road conditions – the damping of the joint is quickly adjusted to compensate as necessary. Within the limits of physics, the articulated bus can thus be very quickly stabilised, so avoiding any see-sawing of the rear section or, in the worst case, the dreaded jackknifing effect. The new ATC anti-jackknifing control system is thus the only system of its type to achieve anything like the effect of an electronic stability control system (ESP).
This represents a new level of safety altogether for articulated buses. With the move to the new B2E electronics platform, ATC will also be used on the Citaro G.
The new B2E electronics platform
The precondition for ATC and other safety systems is the new B2E electronics structure (Bus Electronic/Electric Architecture), which is currently being introduced across the whole Citaro model family. B2E is a well-honed system right from the start, because although the technology has been configured for buses, it derives in principle from the system used in Mercedes-Benz trucks. In addition, with the shift to Euro VI, B2E has already been tried and tested in the high-deck Mercedes-Benz Travego, amongst others.
This new electronic/electric architecture introduces new control units and a different operating system, but at the same time it brings improvements in quality. So, for instance, a CAN diagnosis protocol is now available, while the auxiliary heater now also offers diagnostic capability through the CAN databus.
Buses featuring the new electronics structure are identifiable by a modified instrument panel with a new multifunction steering wheel and steering-column levers, new instruments with display, modified control buttons and a new control unit for the heating, ventilation and climate control systems, taken from the touring coach models. As with the Citaro, the ignition lock of the CapaCity L is now located on the console between the driver and the side window.
Drivers benefit from a steering wheel with an extended adjustment range. A new feature in the urban regular-service bus is a setting for when the driver takes a break: the steering wheel can be tipped forward into a vertical position to give particularly easy access to the driver's workstation.
Switching does not take much getting used to for the driver
With the exception of the modifications in the cockpit as part of the introduction of B2E, there's not much the driver of a current Citaro G needs to get used to when switching to the CapaCity L. In the one as in the other, the driver sits on a raised pedestal and so at eye level with the passengers. The driver's workstation is spacious as well as ergonomically designed in every respect. The height and angle of the instrument panel, together with the steering wheel, can be adjusted in the familiar way to provide the perfect seating position.
Further features include exemplary visibility to the front and to the side, simple and intuitive controls and a number of practical stowage compartments. As an option the CapaCity L, as also the Citaro, can be fitted with any of a wide range of driver protection doors. The independent front suspension ensures excellent ride comfort, while the integrated front collision guard provides optimum safety for the driver in the event of an accident.
One vital but challenging prerequisite for driving a large-capacity bus safely is to have a perfect overview of the surroundings, particularly the area around the rear section. The design of the CapaCity L, with just one articulation joint, already simplifies the issue of visibility. In addition there are two exterior cameras to the right and left of the rear to provide a view of what's happening around the rear section. As with the conventional articulated bus, the doors are automatically operated. If so required, the driver is able to monitor the interior with the help of cameras.
Powerful and extremely efficient: the engine of the CapaCity L
The CapaCity L relies on proven drive components from the Citaro G, already recognised for their exceptional efficiency. Vertically mounted to the left of the rear section is the six-cylinder in-line Mercedes-Benz OM 470 with a displacement of 10.7 l. This unit meets the Euro VI emissions standard and is available in the two output categories of 265 kW (360 hp) with torque of 1700 Nm and 290 kW (394 hp) with torque of 1900 Nm, so guaranteeing powerful traction, whatever the circumstances. These might include demanding topography plus a full complement of passengers that takes advantage of the impressive permissible gross vehicle weight of 32 t.
Power transmission is the preserve of the tried and tested torque-converter transmissions from ZF and Voith, as used in the Citaro. The shift characteristics of the transmissions have in each case been adapted to the particular demands upon the CapaCity L. While the Voith Diwa automatic transmission in the CapaCity L features a higher-capacity heat exchanger, the ZF Ecolife transmission has been adapted to the new input torque levels and a new control unit fitted that allows flexible oil change intervals. New components result in further improved shift quality.
The new CapaCity L features the highly advanced efficiency technology that has already proved its worth in the Citaro Euro VI. Mercedes-Benz predicts the same for the new CapaCity L: no diesel-powered urban bus uses less fuel per passenger place than the new large-capacity bus.
Particular attention was paid during the development of this new generation of urban buses to ensuring the efficiency of ancillary consumers. In the case of urban regular-service buses, these are responsible for around a quarter of the fuel consumption. Controlled alternators operate more economically, giving them a significantly longer service life. Low entrances reduce both the time spent and the amount of compressed air used for the "kneeling" function at stops. The two-stage air compressor operates more economically and has a longer service life. Similarly, the cooling fan with controlled pump operates more efficiently.
Also worth highlighting is the unique recuperation module, used for additional short-term energy storage alongside the on-board batteries: Supercapacitors (supercaps) store the no-cost energy generated during overrun phases, feeding it back into the system for added support when pulling away or on an incline. During these high-consumption phases, the engine of the CapaCity L therefore does not also need to power the alternators to generate voltage.
Repair and maintenance
In view of the quite common ownership periods for urban regular-service buses of ten years or more, Mercedes-Benz was particularly concerned during the development of the new CapaCity L to ensure the ease of maintenance and repair of the large-capacity bus - an important plus for transport operators. Once again, the CapaCity L benefits in this respect from the Citaro's modular system:
virtually all components with a relevance to maintenance are not only identical, but also share the same location in the vehicle. This simplifies the task in the workshop as well as the replacement part inventory, so reducing costs.
Similarly, both fuel and AdBlue are refilled at the same points as on the Citaro G.
Emphasis on economy
The exceptional economy of the CapaCity L is apparent in other areas too, for it is not only measured in high passenger numbers. The procurement costs for a large-capacity bus are also considerably lower per passenger place than they are for a conventional articulated bus.
Inner values: the interior of the CapaCity L
The extra length of 2.9 m compared with the Citaro G articulated bus or of 1.5 m compared with the previous model gave the developers added scope for designing the interior. Three factors were given priority in the case of the CapaCity L: a flexible design for the passenger compartment to accommodate the varying wishes of transport operators, a layout providing as many passenger seats as possible and, given the large number of passengers, a fast passenger flow.
While the CapaCity has been available until now with a choice of three or four double-width doors, the new larger CapaCity L will in future offer the option of a further five-door version with two doors between the first and second axles, in order to speed up the passenger flow even further on exceptionally popular routes.
The CapaCity L is available with a choice of pneumatic inward folding doors, electrically operated pivot-and-slide doors, or a mixture of these two styles. In addition, a third option of electrically operated inward folding doors is currently under development.
Flexible design for the passenger compartment
The different layouts for the passenger compartment give the new CapaCity L great flexibility in meeting the requirements of its operators. Back as far as the second axle, the interior design is exactly the same as for the Citaro in its guise as a rigid or articulated bus. The forward part of the rear section includes an additional standing area opposite the door.
The basic layout lends itself to numerous different permutations. Folding seats in the areas for standing passengers add to the bus's versatility. It is also possible to replace the single seats behind the second axle with standing room, equipped as an option with folding seats as well. The area for standing passengers in the rear section can be extended by shortening the raised platform and removing one pair of seats. As an alternative to the three passenger seats immediately after the fourth door, it is possible to select leaning supports in conjunction with extra stowage space.
The CapaCity L for the model's first customer, public transport operator "Hamburger Hochbahn", is configured to accommodate 165 passengers - 43 seated and 122 standing. This is an increase of 12 passenger places compared with the previous model, and of 39 places compared with the Citaro G with a comparable layout and drive system. This CapaCity L demonstrates its tremendous flexibility with a further eleven folding seats in the passenger standing area. The basis for these calculations is a realistic figure of six people per square metre. In purely arithmetical terms, the capacity at the permitted level of eight people per square metre would increase by 14 places to 179 passengers.
CapaCity L – perfect for the requirements of BRT systems
All in all, the new CapaCity L lends itself perfectly to use on busy routes and in BRT systems. Its low-floor concept over the full length of the passenger compartment is designed for accessibility and so also ideally suited for passengers with restricted mobility.
The pleasant and open design of the passenger compartment makes it appear welcoming. Curved and clearly positioned grab rails are not only a safety factor, but also provide visual guidance for passengers making their way through the bus. The horizontally mounted grab rails are oval in section and pleasant to the touch. The generous standing height of around 2.3 m adds to the pleasant and airy sense of space, even with a large number of passengers on board.
At the instigation of transport operators, the developers have paid particular attention to providing standing room for a large number of passengers. The CapaCity L achieves an exceptionally high level of variability thanks to optional folding seats in the standing area and the single seats in the rear part of the front section.
Sophisticated climate control for the large-capacity bus
Although in most cases passengers will only spend a few minutes each day on the CapaCity L, Mercedes-Benz has put a lot of thought into designing the climate control system.
Electric side wall radiators and a high-performance auxiliary heating system work quickly and efficaciously to keep the large-capacity bus at the right temperature. Top-hung windows, air ducts with ventilation openings, electrically operated roof hatches and roof fans ensure the effective flow of fresh air.
Worth noting is also the powerful optional air-conditioning system with integrated roof heater for the CapaCity L, which has a cooling capacity of up to 43 kW (by comparison: Citaro G 38 kW) and is thus able to cope with the high demands made of it even in climatically challenging regions.
CapaCity L joined by the more compact CapaCity
Despite the numerous advantages of the CapaCity L large-capacity bus, not every transport operator necessarily needs its enormous capacity, even at peak times. Nor is the required infrastructure, in the form of bus stops, workshops and depots, available everywhere for a large-capacity bus with a length of 21 m. Mercedes-Benz therefore plans to expand its range of articulated buses in due course with a further, more compact version of the CapaCity.
This CapaCity will be 19.7 m long and will plug the gap between the Citaro G articulated bus (18.1 m) and the CapaCity L (21 m). The only technical difference will be the omission of two segments from the front and rear sections of the CapaCity L. All other design features, including the four-axle version and the arrangement of doors and powertrain system, will be retained. With this step, the wheelbase between the second and third axles will shrink from 7260 mm to 5990 mm. At the same time the turning circle will be reduced from 24.47 m to 22.93 m, so further improving manoeuvrability, particularly in narrow city streets.
CapaCity L: extensive and thorough test programme
When developing the CapaCity L, the development team were able to benefit both from the extensive experience made with the previous model and from the step-by-step introduction of the new generation of Citaro buses.
Nevertheless the CapaCity L, too, was subjected to a range of very thorough function tests and real-life testing. As with the new Citaro, these ensure top quality right from the start of series production.
Extensive winter testing in Scandinavia, focusing on the suspension and handling as well as on the heating systems, was as much a key part of the programme as was comprehensive practical testing of the brakes, the steering of the trailing axle and of electronic/electrical systems.
A further important test will be the forthcoming customer trial in real-life use on regular-service routes with passengers on board. This will be undertaken by the CapaCity L with the public transport operator in Hamburg, "Hamburger Hochbahn".
This trial period is initially set to last for two weeks. To be continued: the next stage will see intensive customer trials with further vehicles next spring. This real-life testing will allow the new Mercedes-Benz CapaCity L to demonstrate its true greatness.
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