The tyred tram , also called road transport guided , is a hybrid vehicle of Public transport, located between the Autobus and the Trolleybus, with which it divides the bearing on pneumatic, and the Tramway, with which it shares guidance and the Power supply.

It belongs to the big family of the Bus to high level of service (BHNS)

Networks of tyred trams

See also: List of the tyred trams

History of the concept

The traditional Tramway, which had almost disappeared in France in the years 1960 (persisted only one line with Marseilles and Saint-Etienne, a line in Y - the Mongy - with Lille - Roubaix - Tourcoing), returned on the urban scene in the middle of the Années 1980, initially with Nantes, then Grenoble, then in several other cities then. Synonym of transport modern, effective, comfortable, fast and quiet, like decisive urban modernizations (pedestrian spaces, plantations of trees, refittings of places…), he now is recognized and appreciated of the public. Effects of mode: in the years 1950, in fact the trolley bus was " rapid and confortable" , and which détrônait the tram (see the press of the time).

For a few years, one has attended an important technical innovation directed towards hybrid systems, in the hope to benefit from the advantages of the tram without undergoing all the constraints of them. Thus was born for the network from Nancy, an intermediate system re-using the air lines of contact of the network of Trolleybus, profiting from a mechanical guidance in downtown area (for an adjustment perfect with the quays), consisted a body of tram, but provided with tires, poles and of a wheel, like a trolley bus. The general-purpose character of this vehicle makes it possible successively to use it like:

• a diesel-electric Bus, in autonomous mode not guided;

• a Trolley bus, in not-guided mode (with food by poles);
• a Tram, in guided mode, by the design of the cases of the vehicle.

In front of the success of the tram and antédédent it created by this system, Irisbus decided to also name “tram” its Trolleybus with optional optical guidance. Name tram is contestable from a linguistic point of view, because the tram is defined by the Railway on which it rolls, railway which is lacking with the tyred tram: this one rolls on the roadway with pneumatic and has only one central guide rail, even a simple trace of optical guidance, which constitutes a railway by no means: impossible to turf a tyred tram line, for example.

According to the networks, the choice could be made exploit only one or more these possibilities:

• without guidance:
• autonomous traction (diesel-electric);
• electric traction with food by poles.
• with guidance:
• autonomous traction (diesel-electric) (in the absence of tension with the overhead line, or déperchage);
• electric traction, by poles or pantograph:
• the choice of the pantograph determines an overhead line much lighter, (simple and without curved rigid parts in the turns) but prohibited the power supply on the not guided portions,
• the choice of the poles is essential to profit from the electric traction on the not-guided portions (case of the tram of Nancy, whose strong declivities are except guidance). The overhead line will be then heavier, because double.

Technology

The tyred tram is guided either by a roller according to a central Rail (mechanical guidance), or by an optical cell according to a feature traced on its way (optical guidance). It is thus a system between the Autobus, the Trolleybus and the traditional Tramway. One can distinguish three degrees from them.

Optical guidance

A camera is installed in front of the oar locating a marking painted on the roadway.

See also: optical Bus guidé#Guidage

Guidance disengageable central rail with case of traditional design tram

It is the system of Nancy or Caen for example. One put tires on a tram, and added the central guidance system by rail and rollers. This vehicle can be freed from the rail.

This possibility of avoiding an obstruction or of circulating in road mode between two guided portions imposes on the other hand that these vehicles have the homologation of the Mines for a circulation on the public highway, this is why the vehicles of Nancy and of Caen are registered.

Guidance not-disengageable central rail with case of traditional design tram

The system is based on the central rail and the vehicle is designed to function only with this rail (example: new line of Clermont-Ferrand). For this reason, it approaches more of the traditional tram.

This system is directly inspired by the Monorail Larmanjat, whose line was brought into service between Raincy and Montfermeil, in 1868. The system was not a success.

Its the driving main thing is electric. The socket-outlet is generally done by pantograph and Caténaire.

Advantages

This system represents a capital cost potentially less than that of a traditional tram, which is sometimes disputed: the made saving depends much on technology used. Indeed, two networks TVR have costs of 13,6 M€/km for Nancy and 12,1 for Caen. Contrary, TransLohr of Clermont-Ferrand cost 20,7 M€/km. Knowing that in France the average costs of one kilometer tram are of 22,6 M€, only technology TVR is checked as being less expensive with the investment.

Another put question is that of the maintenance costs, which would be at least as high on the tyred trams as on the trams on iron. It would seem, at least for the TVR, that the costs are higher than those awaited but always lower than those of a tram on iron. Problem: few statistical data exist on these questions, and it is thus difficult to slice.

For certain types of vehicles, it also makes it possible to the oar to punctually leave the initial layout in the event of obstacle on the course (breakdown of the preceding vehicle, for example, use of the Bus deposit or a deposit except agglomeration). This debrayability remains interesting for the communes, like Nancy, which cannot be allowed (for political reasons -- refusal of certain communes -- and geographical -- strong urban density) to have an exclusive right of way on the entirety of the course. Thus, the tyred tram can behave as a traditional trolley (if it is not its size), while forming part of circulation. The high weight (38 tons with maximum loading) and the weak ground clearance of the vehicles require however road installations.

This advantage is not exploitable with TransLohr, which is not disengageable.

Direct consequence of the debrayability and factor of lower costs, the possibility of leaving the initial course at the time of work exempts to deviate the networks buried (water, gas, electricity) during the installation of the tramcar lane.

Moreover, circulating tyred, these oars are able to cross slopes inaccessible to the traditional tram without overcosts, up to 130 millimetres per meter, according to the manufacturers. This argument is also disputed, while being based for example on the “electricos” of Lisbon (line 28) which climb slopes of 135 millimetres per meter, without any toothed rack. The towns of Lausanne, the Harbor and Rouen had, before their suppressions, of the tram lines with slopes similar to those of Lisbon.

The advantage of the tyred tram, compared to the traditional tram, is not to require particular technical amendments to climb these declivities. In fact, these adaptations are expensive, and since they are not necessary on the tyred tram, this one benefits from an advantage of cost.

Another announced advantage of the tyred tram is best grip the ground which allows these vehicles a better acceleration and a more effective Freinage.

Lastly, the tyred tram fits more easily in the cities into the narrow streets, because its radius of gyration is of 12 meters minimum, whereas for a tram on traditional iron it is necessary to count a score of meters.

Disadvantages

Had with the mode of guidance

mechanical A) guidance:

In guided mode, comfort is very disappointing: the roadway orniérant very quickly (about two centimetres in Nancy in 4 years) the tread in guided mode is often fractured, with pot-holes, which requires a regular recharging of the roadway with a specific bituminous product, whose flatness is quite less than that of the original roadway. Moreover, the mode of guidance by central rollers causes movements of rather marked laces as soon as speed rises, pointing out the comfort of the decayed railways. Ultimately, the tram on tire is much more comfortable in not-guided mode (and more rapid, speed not being limited in the turns), i.e. in trolley bus mode.

electronic B) guidance:

Comfort is very good, comparable with that of a bus driven by a highly skilled driver: the trajectory of entry in station is flexible and without jolts. The setting with quay is impeccable and the rise of the travellers, poussettes, PMR is facilitated by it. Safety is improved: the system automatically readjusts on its trajectory a vehicle which in manual control would be isolated. In the event of urgency the driver can avoid an obstacle or a pedestrian by giving a blow of wheel, which disconnects the system automatically; this possibility of operation of emergency avoidance is excluded on the vehicles with mechanical guidance (tyred trams or on iron), captive of their rails.

Because of precision of the trajectory of the ruts can be also formed, however the consequences are less large than on the systems with mechanical guidance: there is no mechanical interaction between the guidance system and the rolling members (wheels), which is not the case for the trams with mechanical guidance. A difference in levelling between the wheels and the guide rail can induce efforts of wrenching on the rail.

Had with the bearing on tires

This system was adopted by the networks of Nancy and Caen, which has problems having caused several interruptions of the service, sometimes for periods of more than 8 months for Nancy, and could cause accidents. These difficulties are probably related to insufficient prior studies, a material of which reliability had not been adequately tested and on errors of design (for example, friction then explosion of the tires of the oar at the time of the entry in station). These vexations harm the image of guided road transport obviously, but they also affect the perception and the confidence of the public with respect to public transport in the cities concerned.

This is why the startup the November 13rd 2006 (the opening of the line being pushed back one month following a derailment during tests the October 2nd 2006) of the project of tyred tram of Clermont-Ferrand, which made the choice of another manufacturer (Translohr), was awaited per many of other communities and specialists to check the reliability of the system. The fact that Clermont-Ferrand is the capital of the French industry of the tire is however not indifferent to the choice of a tyred tram instead of a tram on iron.

The use of tires on a roadway constrained to salt the latter in the event of glaze or of snow, which is not necessary with the rail.

Had with the cost of exploitation

An additional disadvantage is being done day: with the exploitation, this type of line would be more expensive than what was envisaged. It would be due to the fast wear of the guide rollers and the associated rail, with the phenomenon of marked rutting of the roadway, with the fast wear of the tires and the consumption of higher energy, which had with the friction of the bearing on tire (almost double that for the bearing on iron).

Had with the choice of a disengageable guided mode (network of Nancy)

The choice of dual-mode guided/not-guided constrained to adopt the feeding system of the Trolley bus: a pair of Pole S in the place of the pantograph, and thus of the contact systems much heavier: doubles instead of simple, and multiplication of the points of suspension in the curves and addition of curved rigid parts, to avoid the déperchage. Contrary to a pantograph which can be given in contact to any point of the network, the tyred tram with poles can repercher only at predisposed places provided with funnels, which do not guarantee the systematic reperchage. Indeed, the strings of the traditional trolley buses were removed, and the driver does not lay out any more a possibility of a manual reperchage.

The ground clearance extremely weak (as on a Tram standard) claims in not-guided mode of the courses with a roadway of an excellent flatness. The presence of a back of ass (would be this only by change of declivity: case of Nancy right to the top of the Saint-Andrew station) can cause inopportune contacts of the case with the ground.

Had with the limitation of size of the oars

The systems with tires are related to the constraints of road transport (“Mines”) which limits the length and the empty weights and in load of the vehicles. A tyred oar (road) cannot be lengthened, contrary to a traditional tram iron/iron (railway) (example of the network of Montpellier).

The increase in the capacity of a line could thus be done only by the multiplication of circulations, which makes difficult their regulation: at the time of an exit or entry of school or academic (very many throughout the line of Nancy), the first vehicle, of very insufficient capacity, is taken by storm, which slows down much its walk and starts the vicious circle of the delay (exchanges in station blocked by the multitude, closing of the difficult doors…). It is thus not rare to see arriving at the terminus four trams after from/to each other:

1. the first, very overloaded late and,
2. the second, still late, and still overloaded,
3. the third, normally charged, but slowed down by the precedent,
4. and the fourth, at the hour, but almost empty.

This recurring situation leads many potential users to be diverted transport in commun runs in rush hour, the length of trip not being reliable (from 9 to 25 mn for a way given (example of Exelmans - > Brabois, in Nancy) , to which 2 will be added to 12 mn of waiting instead of the 4 to 6 minutes of interval envisaged, that is to say a total time of going way from 9 to 37 mn for the same course.)

The network of Nancy will try, starting from October 30th, 2006, to cure this irregularity, by founding one maximum duration of opening of the doors on arrival in 30 seconds station. Passed this limit, it is not possible any more to reopen them and the tram can leave.

Especially, these problems involved in the regularity are mainly due to a under-capacity of the line: there are not enough oars, and the same problem would arise with a traditional tram iron/iron. The network of Nancy, with an official frequency of a tram every 5 minutes, could easily associate some already existing oars with those, insofar as a line of tram becomes with difficulty gérable if the frequency is lower than 2 minutes. Here, with 5, there is still largely what to make. To multiply the number of circulations is thus not a problem.

Had with the absence of standardization of the system

Lastly, the systems being incompatible between them, it is impossible to change supplier, each one having his quite specific system, contrary to the trams on iron which all are overall compatible between them, subject using same the spacing (metric or standard) and same the voltage supply. That could pose a problem of perenniality of the medium-term system, during the replacement of the vehicles or in the event of constructions of new lines for example (in particular in the event of possible stop of manufacture decided by one or the other of the suppliers).

This incompatibility also appears in the agglomerations wishing to supplement a network of trams by tram-trains. If the division of the infrastructures between Tram and Tram-train is not obvious, it is completely impossible with the systems with tires.

Networks of tyred trams

See also: List of the tyred trams

Related articles

• Road train
• Bus guided
• Translohr
• Transport on reserved way

See too

Internal bonds

• Drunk with high level of service
• Subway on tires
• Trolley bus

Random links:

Marita Koch | Joseph Raybaud | Bend EMP | Court of Appeal of Besancon | Park of Vraincourt