Rubber-tired metro

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Image:Metro Paris rubber wheel.jpg Rubber-tyred metro is a form of rail transport, but using some road technology: the vehicles have wheels with rubber tires (tyres), but using a set of two parallel concrete (e.g. Montreal, Lille, Toulouse, part of Santiago Metro), H section steel (e.g. Paris Métro, Mexico City), or flat steel (e.g. Sapporo) rollways, each the width of a tyre. As on a railway, the driver does not have to steer, because in the case of Paris, Montreal, Mexico City and part of Santiago, Chile, the vehicle has horizontal guiding wheels, also with rubber tyres, rolling along guide bars on both sides of the track. From photos it appears that part of the Santiago Metro has conventional track with a third rail.

The VAL family, used in a number of cities including Lille [1] and Toulouse [2], are rubber-tyred.

Most rubber-tyred trains are purpose-built and designed for the system on which they operate..

Guided buses are sometimes referred to as ‘trams on tyres’, and compared to rubber-tyred metros. See also rubber tired trams

On some systems (e.g., Paris, Montreal, Mexico City and part of Santiago, Chile) there is a regular railway track between the rollways and the vehicles also have railway wheels with larger (taller) than normal flanges, but these are normally at some distance above the rails are used only in the case of a flat tyre and at switches/points and crossings. In Paris these rails were also used to enable mixed traffic with rubber-tyred and steel-wheeled trains using the same track, particularly during conversion from normal railway track. Other systems (e.g. Lille and Toulouse) have other sorts of flat tyre compensation and switching methods.

The vehicle is electric, with power supplied by one, or both, of the guide bars, which thus also serves as the third rail (the current is not picked up through the horizontal wheels, but through a separate lateral pickup shoe). The return current passes through a return shoe to one, or both of the rails, or to the other guide bar, depending on the type of system (as in the case of Lille and Toulouse where there is no conventional track between the guide bars) (VAL)

The advantages of rubber-tyred metro systems include quietness of operation, faster acceleration, shorter braking distances, and the ability to climb or descend steeper slopes than would be feasible with conventional rail tracks. This ability to climb or descend allowed the line 4 Yellow (Montreal Metro) to pass under the Saint Lawrence River within a relatively short distance.

However, there are strong disadvantages as well. Rubber tyres have considerably more friction than the optimal combination of steel wheel on rail, thus leading to more energy consumption. They also rapidly lose their traction advantage under inclement weather (especially snow and ice, and that is why the Montreal Metro was built and will be extended entirely underground). Furthermore, it is a more complex technology, using proprietary components, sharing little standardisation with steel-wheeled systems. Weight advantages are minimal, because the traditional steel wheels and rails are still a part of the system as a safety backup, and are also needed for switching purposes. So, in effect, there are two systems running in parallel. This is expensive to build, install and maintain.

The quality of ride can be variable. Noise levels are also not appreciably lower than most traditional steel-wheeled metro systems and can be higher than some.

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History

Rubber-tyred metro technology was first applied to the Paris Metro, developed by Michelin, who provided the tyres and guidance system, in collaboration with Renault, who provided the vehicles. Starting in 1951, an experimental vehicle operated on a test track between Porte des Lilas and Pré Saint Gervais, a section of line not open to the public. Line 11 Châtelet-Mairie des Lilas was the first line to be converted, in 1956, chosen because of its steep grades. This was followed by Line 1 Château de Vincennes-La Défense in 1964, and Line 4 Porte d'Orléans-Porte de Clignancourt in 1967, converted because they had the heaviest traffic load of all Paris Metro lines. Finally, Line 6 Etoile-Nation was converted in 1974 to cut down noise on its many elevated sections. Because of the high cost of converting existing rail-based lines, this is no longer done in Paris, nor elsewhere; now rubber-tyred metro is applied to new systems or lines only, including the new Paris Metro Line 14.

During the World War II German occupation of Paris, the Metro system was used to capacity, with relatively little maintenance performed. At the end of the war, the system was so worn out that thought was given as to how to renovate the system. At the same time, Charles de Gaulle sought to differentiate the French and their way of doing things, as well as create a morale booster. So the real impetus for implementing this burdensome system was political, not technical merit. Nevertheless, the French have succeeded in propagating and exporting this technology.

Though these systems have a certain novelty and panache to them, they have not been widely adopted, except by the few cities listed below.

The first completely rubber-tyred metro system was built in Montréal, Canada; see Montréal Métro. A few more recent rubber-tyred systems have used automated, driverless trains; One of the first such system, developed by Matra, opened in 1983 in Lille, and others have since been built in Toulouse and Rennes the first automated rubber-tyred system opened in Kobe (Japan) in february 1981. it is the Portliner linking Sanomiya railway station with Port island. (Automated driverless systems are not exclusively rubber-tyred; many have since been built using conventional rail technology, such as London's Docklands Light Railway and Vancouver's SkyTrain.) Most monorail manufacturers prefer rubber tyres.

There are other disadvantages with rubber tyres: The high friction between concrete guideway and rubber tyre requires more traction energy to be consumed. This, in itself, is a disadvantage. There is another one in regard to tunnel ventilation: Eventually all traction energy consumed by the train - except the electric energy regenerated back into the substation during electrodynamic braking - will end up in losses (mostly heat). Especially in frequently operated tunnels (typical metro operation) this is a widespread problem, necessitating ventilation of the tunnels. By using rubber tyres with their higher energy demand, this problem is even aggravated. Another disadvantage is cost: Rubber tyres have high wear rates and therefore need very frequent replacement. Although a steel wheelset is more expensive than a pair of tyres, the frequency of their respective replacements makes rubber tyres the more expensive option. And in addition many rubber tyres for guidance will be needed, too.

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Cities with at least partly rubber-tyred metro systems:

Canada:

Chile:

France:

Hong Kong:

Italy:

Japan:


Mexico:

Switzerland:

Taiwan:

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References

nl:Bandenmetro

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