Paris Metro

[adamskiodp]

Hi folks

 

[GrimsbyPacer]

I've wondered the same thing, it's called the VAL System I think, I'll just check into it...

Edit, it looks like the rollways for the rubber tyres move aswell as the rails. Still not sure though.

 

[edwin_m]

The rubber tyre Paris Metro routes are different from the VAL system. The Metro still has rails and steel wheels, which drop onto the rails in the event of a tyre burst, and according to Wikipedia these are also used to steer the trains at points. The steel rails are located inside the tyre tracks and outside are two elevated rails which I believe provide lateral guidance and also the power feed.

 

[MarkyT]

The rubber tyre Paris Metro routes are different from the VAL system. The Metro still has rails and steel wheels, which drop onto the rails in the event of a tyre burst, and according to Wikipedia these are also used to steer the trains at points. The steel rails are located inside the tyre tracks and outside are two elevated rails which I believe provide lateral guidance and also the power feed.

The VAL system by contrast has a single moving switch blade between two closely spaced steering rails in the centre of the track. These rails are only provided in the vicinity of junctions:

http://upload.wikimedia.org/wikipedia/commons/e/eb/Orlyval_-_Orly-Ouest_-_Aiguillage.jpg

This must be followed by a centrally flanged steel wheeled guidance bogie below the centre of the vehicle that in turn steers the rubber tyred wheels along the desired path.

 

[Peter Mugridge]

That is correct, the lateral guidance and the power supply are a shared function. It's quite an ingenious system really.

 

[Taunton]

Paris Metro is different to VAL.

There are conventional steel rails at standard gauge (so normal trains can also operate), with the narrow roadways (concrete, asphalt or steel mesh), just of tyre width for the rubber tyres, laid just outside. The trains have normal steel wheels (at standard gauge) just inside their rubber tyres, on the same axle, and these are normally just fractionally clear of the rails. At points, which are reduced to a minimum on these lines, the roadways are ramped down just a bit, and the bogie descends onto the normal steel rails and is steered accordingly. If you are in the train you can just feel the small descent, and rise up afterwards. There is a significant speed limit over points.

There are also steel skids under the bogie that run along the conventional rails at all times to operate the track circuits. This is why the conventional rails always look shiny where there are no points, such as in stations.

Outside the main roadways are further ones, metal, at right-angles, which contain the horizontally-mounted rubber guidewheels, which are what keeps the train on track. These are actually the conductor rails, which is why they are metal, and the collector shoe on the train is sideways. As a result conventional trains operating on these tracks also have to have sideways-pointed collector shoes, in addition to their normal ones, which run just clear of the roadways.

The whole thing was designed to facilitate a gradual transition during the changeover phase on the tracks, when conventional trains continue to run until all is complete, and then afterwards as well (eg works trains). The lines which were converted, as opposed to new lines like the 14, all took some years each to convert, working at night. There is a certain progression to the works; firstly the outer guideways have to be installed and made electrically live, then the old 3rd rail is removed, then the roadways are laid. Given that the Paris Metro was originally built with smaller trains and the tracks deliberately laid close together, to stop the main line railways with full sized trains getting running powers over it, it's surprising there is space for it all.

The original concept was trialled on one of the shuttle lines in eastern Paris in the 1950s, and was (inevitably for France) heavily backed by Michelin, supplier of the tyres. If I am not mistaken the tyres on Line 6, last to be converted, which has much outdoor running, have treads on the tyres like on cars, to disperse any rainwater on the roadways, which was not needed on earlier conversions which were wholly underground. The overall intention was to get trains with a much better acceleration performance than the ponderous old classic "Sprague" trains on the Metro. Since then modern traction has equalled the performance of the rubber-tyred trains, so there is no longer any need for the very expensive conversions.

 

[edwin_m]

Yes I can't help thinking the Paris Metro "solution" is simply adding lots of extra weight and cost for very little benefit.

 

[Taunton]

A further additional cost is that the trains use much more electricity, as they don't benefit from the low rolling resistance of steel wheel on steel rail. They have also always been driven very hard, especially in acceleration, which further increases current consumption. There is some advantage in this on the Paris Metro, which has very closely spaced stations (you can often see at least the next station each way, and sometimes a couple, from the platforms).

It was however never quite so apparent how they managed to sell the system to several overseas operators (Montreal, Mexico City, etc) who were building from scratch.

Memories of student days on Paris Line 4 (pre-automatic driving) having just made once again the last service of the evening, waiting on stations that smelled like a tyre depot, then the "Pneu" driven flat out, accelerate-brake, perfectly accurate stops, and the "Bruiteur" for doors closing sounding about 2 seconds after coming to a stand! Mademoiselle riding alongside me never quite had the same interest.

 

[adamskiodp]

Thanks guys

 

[Busaholic]

Memories of student days on Paris Line 4 (pre-automatic driving) having just made once again the last service of the evening, waiting on stations that smelled like a tyre depot, then the "Pneu" driven flat out, accelerate-brake, perfectly accurate stops, and the "Bruiteur" for doors closing sounding about 2 seconds after coming to a stand! Mademoiselle riding alongside me never quite had the same interest.

Yes, a tyre depot where cloves of garlic and a string of onions had been woven into the tyre tread! And even in well-used and populated stations in central Paris, the rats would come out in droves about ten minutes before the last metro. Happy days!

 

[NicholasNCE]

Another advantage of the system is that you get less high-pitched noise than you do with conventional rail, comes in useful on the outdoor parts of line 6 which goes through some quite nice parts of Paris and is at times extremely close to buildings (checkout the approach to Passy station for example).

If I am not mistaken the tyres on Line 6, last to be converted, which has much outdoor running, have treads on the tyres like on cars, to disperse any rainwater on the roadways, which was not needed on earlier conversions which were wholly underground.

On line 6 the metal running tracks are also grooved in order to improve performance in wet conditions, but you still hear the tyres spinning pretty badly on rainy days as the train is pulling away from stations (highest tractive effort).
I think this is due to the "pilotage automatique" (basic automatic driving system) not being able to adapt to the conditions.

 

[Taunton]

The aroma of garlic, dead Gauloises, and umpteen Local Cheeses was indeed ingrained into the bodywork of the classic Sprague stock. On the "Pneu" however the tyre smell seemed to trump them all.

 

[MarkyT]

Further research reveals the VAL technology, developed originally by Matra is now owned by Siemens.

http://memim.com/vehicule-automatique-leger.html

Latest products Cityval and Airval are based on the Neoval collaboration with Lohr Industrie, which substitutes a continuous single centre rail for guidance with flanges acting on either side for the steering along plain track and through junctions.

Interesting from various rendered CGI publicity videos that the middle rail is not shown exactly centrally situated between the running surfaces. I wonder if this gives the option for the steering follower mechanism to 'grab' one of a number of alternately routed middle steering rails for self-switching of vehicles at Junctions. The switching is described in some publicity as 'active', and a vehicle could (say) safely disengage the 'straight on' rail whilst stopped at a station and engage the 'turn left at next junction' rail instead before departure. That might also help explain how the spectacularly short headway merge and join manoeuvre shown in the following video could be carried out.

https://youtu.be/MPJzFQ2k86o?t=2m40s

I can't find any online descriptions or images of the actual switching systems proposed for new Cityval or Airval installations. Pictures of the original Translohr switches used on the surface 'pneumatic tramways' are much easier to find although these are centrally positioned between the running wheels.

http://upload.wikimedia.org/wikipedia/commons/5/57/Translohr-point.jpg

 

[jopsuk]

With regards their braking, some of the stock has stickers inside in multiple languages warning of the braking power!

 

[dutchflyer]

The Paris system was added afterwards-some lines were closed for nearly 1 year to put all the necessary wheels and trackworks in place. They also were able to export it to a few other metro-systems, like Montreal and Mexico-city.
VAL was new from the start. Very tiny trains mostly-looks more like a horizontal lift. Can get extremely crowded in towns like Lille-Toulouse-Rennes.

 

[jamesontheroad]

The Paris system was added afterwards-some lines were closed for nearly 1 year to put all the necessary wheels and trackworks in place. They also were able to export it to a few other metro-systems, like Montreal and Mexico-city.

The Montréal métro is worth a look as well. It's entirely subterranean and entirely rubber wheeled. There's an explanation and photograph of the points operation on Wikipedia here.

Switches use conventional points on the standard gauge track to guide trains. Rubber tires, rolling on concrete rollways, keep supporting the full weight of the trains as they go through switches. Guideways are provided in order to ensure there are no gaps in the electrical power supply.

In terms of other matters discussed above, as in Paris there is much debate about the efficiency of rubber tyres over steel wheels. A fundamental design detail of the Montréal métro is that in many instances stations have been built near the surface, with (for steel rails) quite steep tunnels entering and exiting the stations. As a result, a departing train gains some extra speed (and saves energy) by rolling downhill as it moves off. As it approaches a station, it then slows down by rolling uphill, saving energy otherwise lost through braking.

At the time it was built, this fundamental geometry (?) of the tunnels prevented it from ever being converted to steel wheel operation. Today I believe the technology exists, but there's no real motivation to convert the whole system.

A new fleet of rubber-tyred trains called the MPM-10 (or Azur), made by a Bombardier-Alstom consortium, will enter service in the next year or so.

 

[jopsuk]

the Glasgow subway uses a similar "rollercoaster" height profile but using conventional steel wheels

 

[edwin_m]

the Glasgow subway uses a similar "rollercoaster" height profile but using conventional steel wheels

So does, for example, the Central line. And Crossrail will do the same where feasible. Just look at the DLR to see the sorts of gradients a steel wheel system will cope with even under automatic driving.

 

[Julia]

Memories of student days on Paris Line 4 (pre-automatic driving) having just made once again the last service of the evening, waiting on stations that smelled like a tyre depot, then the "Pneu" driven flat out, accelerate-brake, perfectly accurate stops, and the "Bruiteur" for doors closing sounding about 2 seconds after coming to a stand! Mademoiselle riding alongside me never quite had the same interest.

Just back from a trip to Paris myself - with a couple of trips on line 11 where the MP59 are still plying back and forth, it was quite eye-opening to feel just how hard they are driven in comparison to London tubes, and how little grace is given to people who are not ready to board or alight at the right time! UK elf and safety types would also probably be left gibbering at the thought of door locks being routinely released with the train not quite stationary...