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Rubber-tyred metro
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A Rubber-tyred metro is a form of rapid transit system that uses a mix of road and rail technology. The vehicles have wheels with rubber tyres which run inside a guideway for traction, as well as traditional railway steel wheels with flanges on steel tracks for guidance. 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-tyred trams and Bombardier Guided Light Transit.
History
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. Rubber-tyred metro technology was first applied to the Paris Métro, developed by Michelin, who provided the tyres and guidance system, in collaboration with Renault, who provided the vehicles. Starting in 1951, an experimental vehicle, the MP 51, 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 - Pont de Neuilly in 1964, and Line 4 Porte d'Orléans - Porte de Clignancourt in 1967, converted because they had the heaviest traffic load of all Paris Métro lines. Finally, Line 6 Charles de Gaulle - Étoile - 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 metros are used in new systems or lines only, including the new Paris Métro Line 14.
The first completely rubber-tyred metro system was built in Montreal, Canada; see Montreal Metro. A few more recent rubber-tyred systems have used automated, driverless trains; one of the first such systems, 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.
Technology
OverviewThe vehicle is in the form of electric multiple unit, 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.
The type of guideway used on a system varies between networks. Two parallel rollways, each the width of a tyre are used, either of concrete, H-Shape hot rolled steel, or flat steel. As on a railway, the driver does not have to steer, because the system relies on a redundant system of railway steel wheels with flanges on steel rail tracks. The Sapporo system is an exception as it uses a central guide rail only. The VAL system used in Lille and Toulouse has conventional track between the guide bars.
On some systems (e.g., Paris, Montreal, Mexico City) 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 and 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 essential difference between rubber-on-concrete and steel-on-steel is that rubber-on-concrete generates more friction. This results in various pros and cons.
AdvantagesAdvantages of rubber-tyred metro systems (compared to steel wheel on steel rail):
- Smooth ride (with little "jostling" around)
- Faster acceleration
- Shorter braking distances, allowing trains to be signalled closer together
- The ability to climb or descend steeper slopes (~gradient 13%) than would be feasible with conventional rail tracks.
- Quiet ride in open air (for residents and those outside the train)
- Modern steel-on-steel rolling stock using distributed-traction with a high-proportion of powered axles, have narrowed the gap to the acceleration/performance found in rubber-tyre rolling stock.
DisadvantagesThe higher friction causes disadvantages (compared to steel wheel on steel rail):
- Higher energy consumption than steel-on-steel
- A larger quantity of excess heat is generated
- Weather variance. Losing the traction-advantage in inclement weather (snow and ice)
- Heavier; steel rails remain for switching purposes, and as a safety backup
- Tyre replacement cost
| | 1. | To reduce weather disruption, the Montreal Metro runs 100% underground. On Paris Métro Line 6, upgrades of tyres (as used with cars) and special ribbed tracks have been trialled. | | In effect, there are two systems running in parallel. This is more expensive to build, install and maintain. | | 3. | Rubber tyres have higher wear rates and therefore need more frequent replacement. Although a steel wheels set 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. |
Although it is a more complex technology, most rubber-tyred metro systems use quite simple techniques, in contrary to guided buses. Heat dissipation is an issue as 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). In frequently operated tunnels (typical metro operation) the extra heat from rubber tyres is a widespread problem, necessitating ventilation of the tunnels.
Similar technologiesAutomated 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, as well as AirTrain JFK which is linking JFK Airport in New York City with local subway and commuter trains. Most monorail manufacturers prefer rubber tyres.
List of systems| Country | City/Region | System | Technology |
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| Montreal | Montreal Metro | Michelin | | Santiago | Santiago Metro (Lines 1, 2 and 5) | Michelin | | Laon | Poma 2000 | Cable-driven | | Lille | Lille Metro | VAL 206, 208 | | Lyon | Lyon Metro (Lines A, B, and D) | Michelin | | Marseille | Marseille Metro | Michelin | | Paris | Paris Métro (Lines 1, 4, 6, 11, and 14) | Michelin | | Paris | Orlyval | VAL 206 | | Paris | CDGVAL | VAL 208 | | Rennes | Rennes Metro | VAL 208 | | Toulouse | Toulouse Metro | VAL 206, 208 | | Turin | Metrotorino | VAL 208 | | Kobe | Kobe New Transit | | | Port Island Line | Kawasaki | | Hiroshima | Hiroshima Rapid Transit | | | Astram Line | Kawasaki / Mitsubishi / Niigata Transys | | Sapporo | Sapporo Municipal Subway | Kawasaki | | Tokyo | Yurikamome | Mitsubishi / Niigata Transys / Nippon Sharyo / Tokyu | | Nippori-Toneri Liner | | | Mexico City | Mexico City Metro | Michelin | | N/A | Light Rail Transit | Bombardier / Mitsubishi | | Taipei, Taiwan | Taipei Rapid Transit System|Muzha Line]]) | VAL 256
(will be replaced by Bombardier's CITYFLO 650 in 2009) | | Chicago, Illinois | Airport Transit System | VAL 256 |
Under construction
Planned
See also- VAL (Véhicule Automatique Léger)
External links
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