FACTS ABOUT ARTICULATED BUSES Over the past twenty years, there Savings in total kilometre costs. has been a steep rise in operating costs and personnel costs for bus traffic services. Another influential factor has been the shortage of personnel. Demands for better public transport are escalating due to increase in the number of traffic jams in city areas and increasing cost of fuel. Develop­ ments will soon make it impossible for Each column represents a different network. people to drive to work in their own Savings in costs for service personnel. cars. The difference between heavy and light traffic has also been emphasized. During peak hours, it is often necess­ ary to have twice the capacity needed for light traffic. And in this context, the shortage of personnel is becoming an increasingly difficult problem. One way of increasing transpor­ Each column represents a different network. tation capacity is the use of larger vehicles which is a good solution, Savings in costs for technical maintenance. especially during peak hours. This is where articulated buses give a practical solution. Using the same number of personnel, having almost the same operating costs as two-axle buses, the passenger carrying capacity can be in­ creased by 50% to 75%. The information referred to in the following diagrams has been extracted Each column represents a different network. from U IT P ’s (International Union of Savings in fuel costs. Public Transport) report “Technical and economic aspects of articulated b u ses”, which was given at the Inter­ national Congress in Helsinki, Finland 1979. The diagrams indicate the savings that can be achieved by use of articu­ lated buses, as compared to standard, 11 m, buses, costs per passenger have Each column represents a different network. been used as comparative units. The Savings in costs for tyres. costs have been obtained from 17 to 27 transport authorities throughout the world.

Each column represents a different network. Different types of articulated buses have been developed over the years. Here, you can see 6 different types (UITP report):

A. Front end horizontal under floor axial engine with the second axle powered.

Bl. Vertical front engine with second axle powered.

B2. Side mounted engine with second axle powered.

C. Rear engine with third axle powered.

D. Rear engine with second axle powered.

E. Engine immaterial, with hydrostatic or elec­ tric transmission..

All these different types have their This has also been confirmed by advantages and drawbacks. Scania- bus owners. Sales of Scania rear engine Bussar have chosen method C, i.e. an chassis have soared. articulated bus with a rear engine, and And consequently, it was natural with the third axle powered. This type for Scania to develop the new articu­ is known as a “pusher” bus. lated bus on a rear engined chassis. Scania-Bussar already understood S can ia’s articulated, pusher bus was the advantages of rear engine buses at presented in conjunction with the an early stage, because with the engine UITP-Congress in Helsinki, 1979. The at the rear, the bus can be built to meet bus was a Jonckheere Trans City, built individual body design requirements. on a Scania BR 112 A chassis. S can ia’s articulated bus chassis prototype, even though all construc­ became a branch topic, right from the tions had not yet been tested. Today, start. And a large number of chassis they have. were sold merely on the basis of the

OPERATING FLEXIBILITY. Scania BR 112 A is built for silent Articulated buses can operate in running. Noiseless for the driver and practically all types of traffic con­ the surroundings. T h a t’s why there is a ditions. Scania BR 112 A makes it tachometer on the instrument panel; feasible to build a bus with a low floor the driver can’t hear the engine. for city traffic (city version). And for suburban services and route services, or route services and private coach services, there is BR 112 A with a normal floor and with space for a luggage compartment under the floor Thanks to the rear mounted (normal version). engine, it ’s easy to sound-proof the engine compartment. Consequently, PERFORMANCE AND Scania BR 112 A is delivered with a ENVIRONMENTAL FEATURES. completely sound-insulated engine room, and with instructions for the coach makers regarding the com­ pletion of the sound-insulating work, so that a bus with no more than around Bearing in mind that the total 77 dB (A) noise level is obtained. weight may exceed 26 tons, the drive line components must satisfy the STANDARDIZATION IN RELATION demands for good acceleration, as well TO TWO-AXLED BUSES. as for high speed. Scania BR 112 A is Bus companies require as much delivered with a turbocharged, 191 kW uniformity as possible in respect of (260 hp ISO), DS 11 engine for maxi­ parts supply, servicing methods and of mum fuel economy. The automatic course good public image. There will gearboxes, 3-shift or 4-shift, live up to then be no need for the retraining of engine performance. The Scania BR drivers. They can switch from a two- 112 A accelerates swiftly, smoothly and axled bus and straight away take over can be driven at high speeds. a three-axled articulated bus. without any difficulties about super­ vising bus movements. Safety wise, it ’s also important that the sweep area is the least possible when cornering, changing lanes, pulling in or out of bus stops, bearing in mind surrounding traffic and pedestrians. In a steering geometrical sense, i t ’s possible to differentiate between articulated buses with a steered rear axle and those with a rigid rear axle. An articulated bus is of course Utilizing a rear engine and the third longer, so the driver has to take this axle powered, you are in practice into consideration in certain situations forced to use a rigid rear axle. And during a run, but other operating charac­ consequently, Scania BR 112 A has this teristics, such as instrumentation, feature. fittings, controls etc., should be more or less the same for an entire fleet.

RIDING AND DRIVING COMFORT.

The advantage offered by an Naturally, riding and driving com­ articulated bus with a steered rear axle fort should be equal to that of two-axle is a smaller sweep width (distance between outer and inner turning buses. I t ’s important to passengers that access step height is low and convenient. circle). But the difference is rather The bus must also be well suspended modest, around 0.7 m,when compared to S ca n ia ’s new articulated bus. have excellent stability and road hold­ ing so that it d oesn ’t sway when cornering or wander at high speeds. From the driver’s viewpoint, i t ’s important that the bus has good road holding characteristics, and that it per­ forms in traffic like a two-axle bus in most situations. Neither should the driver have any cause to be uncertain about what happens, when he brakes heavily on icy roads, or when he has to S can ia’s new articulated bus satis­ drive up a slippery slope for instance. fies the EEC-regulations, which stipu­ late that in stabilized cornering, it STEERING GEOMETRY must be possible to drive a bus CHARACTERISTICS. between two circles with radii of 12 m Drivers, depot and workshop and 5.3 m, whether the bus has two personnel prefer a type of articulated axles or several axles. These regula­ bus that can be driven in the same tions regarding sweep width will be places, and use the same stops, as two- adopted by an increasing number of axle buses. This should be feasible, countries. our opinion, than that of a steered rear axle articulated bus. A driver always knows what is happening to the rear part of a pusher articulated bus. He can supervise everything with the help of the side mirrors, something he can­ not do, however, on a steered rear axle articulated bus. I t ’s also a fact that a pusher articu­ lated bus d oesn ’t attain its full sweep until the bus has made about a half- An articulated bus with a steered turn. But long curves are few and far rear axle has a drawback, since the between. Therefore, under normal con­ rear section sweeps over the kerb when ditions, a pusher articulated bus can the bus pulls out from the bus stop. utilize the same manoeuvring areas as The maximum permissible oversweep a common two-axle BR 112 bus. is 1.2 m according to EEC-regulations. I t ’s even easier to reverse Scania BR 112 A, but on the other hand it requires more space for turns on straightening, than a steered rear axle articulated bus.

WEIGHT DISTRIBUTION. The weight distribution on an articulated bus should be arranged so that the drive wheels always have sufficent tractive force. There should also be a good distribution of the braking force. It must be possible to In this case, S ca n ia ’s new articu­ use the retarder, without running the lated bus even satisfies EEC regu­ risk of jack-knifing on slippery roads. lations for two-axle buses, for which the maximum permissible oversweep It is a well known fact that articu­ is 0.8 m. As a matter of fact, the over­ lated buses with the second axle sweep of S ca n ia ’s articulated bus is powered often have starting problems less than that of a two-axle bus. on slippery road surfaces. In the case of Scania BR 112 A, however, you get sufficient pressure on the powered axle, A Scania BR 112 A has a larger even on an empty bus. sweep width. To compensate this, the In addition, Scania BR 112 A has first buses have been shortened by an adequate positive load, which is around 60 cm, to 17.4 m. On the other applied to the pivot by the rear coach. hand, a steered rear axle articulated One m anufacturer’s articulated bus bus has tapered coachwork comers to constmction has actually resulted in a reduce the drawback of body over negative load on the pivot. And this swing when cornering, changing lanes, has influenced the performance to pulling in or out at bus stops and in such an extent, that it has been found order to retain the maximum permiss­ necessary to limit the speed of that bus. ible length of 18 m. When braking, it is advantageous Which drawbacks are the easiest to have an axle load distribution at the to accept? rear, where the heaviest weight is and The wider sweep of a pusher consequently, the highest braking articulated bus is more acceptable, in force. Furthermore, there is an advan- speeds are fitted at the pivot. The curve of the fold-absorbers allows them to follow closely at low folding speeds, but also to absorb and even lock at jack-knifing. tage in that the gearbox retarder works on the right axle, i.e. the third axle. A retarder on the second axle increases the risk of jack-knifing on slippery roads. Scania BR 112 A has a good basic 2. The throttle is electronic and is stability, as a result of its advantageous connected to a control box, which is weight distribution: 4,000 kg at the also fed with data about the pivot- first axle 4,345 kg on the second axle angle. Excessive acceleration is elec­ and 7,750 kg on the third powered axle. tronically blocked in conjunction with These figures apply to the service big pivot-angles. This electronic control weight of the first Jonckheere-body, cuts out at speeds of less than 7 km/h. which was built in a de luxe version for route and tourist traffic.

ROAD HOLDING STABILITY. The running characteristics of an articulated bus must induce a feeling of safety in the passengers. They must 3. Another electronic system feel that the bus is safe and stable, registers the revolutions of the third independent of speed or road con­ axle (powered) and compares them ditions. Scania BR 112 A displays an with those of second axle (using known excellent road holding stability, even at techniques from locomotives and non­ high speeds and in trials on skid pads. locking brakes). If the rate of revolution does not fall within the permissible SAFETY AGAINST ratio, the fuel is automatically cut off UNCONTROLLED JACK-KNIFING. and a multi-disc, lamina brake in the pivot is engaged (the same type of brake employed on long-distance, semitrailer tmcks). This makes it pos­ sible to avoid e.g. jack-knifing, when there are differences between the tyre grips under the second and third axles. An articulated bus should be built in a way that makes it possible to avoid jack-knifing even if the driver makes obvious mistakes, or if road con­ ditions are unfavourable. Scania BR 112 A has a basic design 4. The pivot brake is activated also that results in a steady running bus, at high braking pressures. This means well adapted to all traffic situations. that when a driver brakes heavily, In addition, the following extra there is no risk of the rear being swung safety devices have been introduced on outwards. Scania BR 112 A, so that it can operate safely, even in extreme situations. These features ensure that Scania BR 112 A mns safely in all road con­ 1. Horizontal fold-absorbers that ditions for all drivers. counteract high folding (jack-knifing) SUMMARY. ARTICULATED BUS CHASSIS SCANIA BR 112A.

Scania BR 112 A has the same • Scania BR 112 A has an electronic standard components as Scania BR 112, throttle. Cables and tube extension regarding steering parts and drive kits are delivered for bus lengths of parts. Consequently it also has the up to 18 m. same advantages as a common rear- • The tachometer is standard, since engined bus: the engine is so far away from the • Weight concentration above drive driver. wheels which results in even tractive • The braking system is a two-circuit force. system. One circuit works on the first • Engine is easily accessible for service. and third axles, and the other on the • Engine compartment is easy to sound second and third axles. proof and gives lower noise level. • Brake linings on first, second and • Low floor for city services, high floor third axles are 7", 8" and 10" respect­ for route services, when ample space ively. for luggage is required, can be • There is an extra compressed air tank adapted due to rear mounted engine. for the extended braking system. • The driver enjoys a quiet environ­ • High folding (jack-knifing) is counter­ ment. acted by horizontal fold-absorbers, • It differs from a normal two-axle pivot-angle controlled throttle, Scania BR 112 in that only a middle lamina brake in the pivot and a axle and a turntable are added. The sensor comparing the revolutions middle axle is a Scania standard trailer of the second and the third axle. axle of type AT 90. It has air suspen­ • Scania BR 112 A is sion with roller bellows as the other available in two ver- m axles. sions. A city • The turntable with its frame, and the version with entire intermediate construction, a low floor, are manufactured by Schenk, E u rop e’s largest manufac­ turer of these parts. • The 300 litre fuel tank is positioned behind the turn­ and one with a somewhat table, in order to obtain a higher floor, with space for good pressure on the luggage compartment under middle axle and the floor. pivot centre. • The tyre sizes are the same as Scania BR 112, i.e. 11-22.5 on all wheels, with twin tyres on the second and third axels. • Maximum gross vehicle weight is 26.5 tonnes having an axle distri­ bution of 6,000 kg on the first, 10,000 kg on second and 10,500 kg on third.

SCANIA SCANIA-BUSSAR AB, KATRINEHOLM