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International trade show début at the UITP congress: more space for the city – the Mercedes-Benz CapaCity L large-capacity articulated bus
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- Space for up to 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
- Inner values: the interior of the CapaCity L
More space in the urban bus: in its standard version, the new Mercedes-Benz CapaCity L can accommodate up to 191 passengers. Developed for exceptionally busy routes, this large-capacity articulated bus is great in many respects. It offers great manoeuvrability, for the CapaCity L is agile despite its length of 21 m. Moreover, the CapaCity L is great in extreme driving situations: with its new Articulation Turntable Controller (ATC) and the ingeniously steered fourth axle, it sets the benchmark for safety and handling. Economy is great, too: the CapaCity L is based on the modular system of the best-selling Mercedes-Benz Citaro. By contrast, fuel consumption and emissions are small: no other diesel-powered urban bus uses less fuel per passenger space.
Growing demand for large-capacity urban regular-service buses
Sometimes, 'big' is just not big enough, and at that point even the capacity of the spacious 18.1 metre-long Mercedes-Benz Citaro G articulated bus is overstretched. On busy bus routes this is particularly relevant during the rush hour. 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.
A giant on wheels with a concept that is made to measure
At the request of transport operators, the new Mercedes-Benz CapaCity L has grown even further compared to its predecessor. Measuring exactly 20,995 mm in length, it is around 1.5 m bigger 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. Due to the amount of well-proportioned space in the passenger compartment, in its standard version it can accommodate 191 passengers.
Sheer size and a large capacity alone, however, are not enough for a highly specialised large-capacity bus concept. A careful balance needs to be achieved in terms of dimensions, axle arrangement, steering, drive system, door placement and the design of the passenger compartment. The demands in terms of manoeuvrability are obvious. Further factors of particular importance to operators include ease of maintenance and repair and economical powertrain systems, through to the necessary traction and safety in critical road conditions. The new Mercedes-Benz CapaCity L brings all these elements together in a single coherent whole.
Large-capacity bus built on the modular system
The CapaCity L is based, both visually and technically speaking, on the platform of the best-selling Citaro G, already proven many thousand times over. Up to and including the centre axle, the front section is identical. The rear overhang, too, corresponds to that of the familiar urban bus. Primarily the CapaCity L differs with respect to the additional segments at the end of the front section, in the front part of the rear section and the extra fourth axle. This ensures a harmonious distribution of weight.
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. The new CapaCity L can be customised as an alternative to the standard design. The Metro design package includes side panelling for the bus's individual roof attachments. 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.
If desired, transport operators can also fit the CapaCity L 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 its large wheel angle and the 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 is 24.47 m, while the minimum turning track within the turning circle is 7.1 m. The CapaCity L therefore does not require any special exemption in relation to its turning circle.
The only exemption needed in the case of the large-capacity bus relates – as for 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. The new steered trailing axle features independent suspension. It combines exceptional suspension comfort with superb handling and low tyre wear.
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. At driving speeds of over 40 km/h, the steering of the trailing axle is automatically centred. This optimises straight-line stability further and thus handling.
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 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. If necessary – for example when the steering wheel is turned fully immediately upon pulling away – the driver can 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.
Unique anti-jackknifing system ATC 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. 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 articulated joint as a function of the steering angle, articulation angle, speed and load.
As a result, 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 understeer/oversteer characteristics and steering effort, with the result that the responsiveness and steering forces of the articulated bus are virtually on a par with those of a rigid vehicle. 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 stabilised, so avoiding any see-sawing of the rear section. The new ATC anti-jackknifing control system is the only system of its type to achieve anything like the effect of an electronic stability control system (ESP).
Swift familiarisation at the wheel of the new bus
There is not much that the driver of a current Citaro G needs to get used to when switching to the CapaCity L. In both vehicles, the driver sits on a raised platform and so at eye level with the passengers. The driver's workstation is spacious and absolutely ergonomically designed. The height and angle of the instrument panel, together with the steering wheel, can be adjusted 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 facilities. As an option the CapaCity L can be fitted with any of a number 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. 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 at the rear to provide an overview of what is happening around the rear section.
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 high 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 litres. 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. Power transmission is the preserve of the tried-and-tested automatic transmissions with torque converter from ZF and Voith. The shift characteristics have been adapted to the particular demands upon the CapaCity L.
The CapaCity L features the highly advanced efficiency technology that has already proved its worth in the Citaro Euro VI. Particular attention has been paid to the efficiency of auxiliary consumers. In the case of urban regular-service buses, these are responsible for around a quarter of fuel consumption. Also worth mentioning is the unique recuperation module, used for additional short-term energy storage alongside the on-board batteries: supercapacitors (supercaps) store the energy generated during overrun phases, feeding it back into the system when pulling away or on an incline as electricity for auxiliary consumers. During these high-consumption phases, the engine of the CapaCity L therefore does not also need to power the alternators to generate voltage.The result of all these efficiency measures? No diesel-powered urban bus uses less fuel per passenger place than the new large-capacity bus.
In view of long 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 ease of maintenance and repair for the large-capacity bus. Once again, the CapaCity L benefits in this respect from the Citaro's modular system: virtually all components of 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 storage of parts, so reducing costs.
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 accorded priority in the case of the CapaCity L: flexible design of the passenger compartment, room for as many standing passengers as possible and fast passenger flows.
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 to passengers with restricted mobility.
Whereas the previous CapaCity optionally had either three or four double-width doors, a five-door version of the new larger CapaCity L will additionally be available in future if required. The different layouts for the passenger compartment give the CapaCity L great flexibility in meeting the needs of its operators. Back as far as the second axle, the interior design is exactly the same as for the Citaro. 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.
CapaCity L to be 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 remain the same – including the four-axle construction. 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.