TGV signalling - how is the driver informed of their actual route?

[30907]

My daughter is currently on the afternoon AVE Madrid-Avignon(-Marseille) which was misrouted at the Avignon triangle and is currently sat North of Orange (there are loops and crossovers there, first after the junction!) waiting for the train to reverse and head back South (minimum +60 so delay repay kicks in). Edit - which it now is!

Described by the crew as a hardware failure.

So - how does the TVM cab signalling inform the driver of the route that is set, as opposed to the speed? Obviously at TGV speeds you can't check the points are set! A quick glance at a well-known, never inaccurate, online source doesn't say. Any SNCF experts here?

Thanks in advance.

 

[MarcVD]

As far as I know, there isn't any. TGV SNCF is entirely a speed-signalling affair. And I don't believe there is anything foreseen for that in ETCS either.

 

[hexagon789]

TVM-430 doesn't inform the driver of the route, only the maximum permissible speed.

Classic French signalling does however give a route indication like British practice, in contrast to the usual pure speed signalling used in most of Europe.

 

[duesselmartin]

is route indication a necessity?

 

[Adlington]

is route indication a necessity?

Well, most of Europe somehow manages without it....

 

[martin2345uk]

I guess without route indication 100% of the "blame" goes to the signaller, as opposed to being shared with the driver as here.

 

[Beebman]

I've often wondered what happens at a junction with two diverging routes each with the same speed - does the driver simply have to trust the signaller?

 

[Austriantrain]

Classic French signalling does however give a route indication like British practice, in contrast to the usual pure speed signalling used in most of Europe.

How so? (Really interested).

I've often wondered what happens at a junction with two diverging routes each with the same speed - does the driver simply have to trust the signaller?

Sure. There is no real issue with it - the driver is responsible for adhering to the signaled speed, which will be right for both routes.

 

[edwin_m]

With pure speed signalling there's a risk of a train being incorrectly sent onto a route it isn't allowed to use, for reasons such as bridges with axle load limits or lack of electrification. Not an issue for LGVs and I suspect such restrictions are rarer on the Continent than in the UK, but probably exist somewhere. There's also an extra risk that if a train is misrouted the driver doesn't know until the junction itself, so continues further down the wrong route before it stops and takes longer to recover from the incident.

 

[hexagon789]

is route indication a necessity?

With route-based signalling as in British, Irish and some other places practice, it is a necessity!

With speed-based signalling, no it isnt.

How so? (Really interested).

With route indicators or un indicateur de direction

The older style is essentially a post with a display that lights up a horizontal row of 2 to 6 two white dots.

The route indication is based on the way the route travels not the lay of the junction. So if the train diverges right but the route actually turns left, the indicator will display left.

At higher speed junctions an advance indicator is used which displays an arrow indication showing the set route.

At all times however, the diverging speed is also shown to the driver through signal indications as well.

Classic French railway signalling is therefore generally described as a hybrid of speed and route signalling.

 

[Austriantrain]

With pure speed signalling there's a risk of a train being incorrectly sent onto a route it isn't allowed to use, for reasons such as bridges with axle load limits or lack of electrification. Not an issue for LGVs and I suspect such restrictions are rarer on the Continent than in the UK, but probably exist somewhere. There's also an extra risk that if a train is misrouted the driver doesn't know until the junction itself, so continues further down the wrong route before it stops and takes longer to recover from the incident.

One instance of this happening was on the first regular Zürich- Munich electric train, which at Hergatz was routed on a catenary-less track. The driver was partly blamed, since he should have known that the signaled speed would mean a wrong route setting.

With route indicators or un indicateur de direction

The older style is essentially a post with a display that lights up a horizontal row of 2 to 6 two white dots.

The route indication is based on the way the route travels not the lay of the junction. So if the train diverges right but the route actually turns left, the indicator will display left.

At higher speed junctions an advance indicator is used which displays an arrow indication showing the set route.

At all times however, the diverging speed is also shown to the driver through signal indications as well.

Classic French is therefore generally described as a hybrid of speed and route signalling.

Thanks a lot!

 

[SHD]

On TVM-signalled high-speed lines, drivers may often infer the route direction from the speed indication (the points are typically designed for 230 km/h or 170 km/h at the diverging position). But indeed, there is no in-cab route indicator.

 

[MarcVD]

The Belgian signaling system also had route indication foreseen when it was created, just after WW2. But it did not last very long, some 10 years, and disappeared shortly thereafter, as it was deemed unnecessarily complex. It was done with an additional board on the top of the main signal board, displaying arrows at different angles to indicate which route was set. This board has since then diminished in size to indicate only right/wrong main track choice. I could not find a picture of that, but I have the schéma that was included in the signaling book of rules at that time :



For those interested, here is a French signaling with direction indicator on top of it :

 

[30907]

Thanks everyone. Very interesting.

I suspect the driver may have had a clue in the speed profile, but that could have had another reason.

For info, the train was only +45 or so when it got back to Avignon-TGV.

 

[Towers]

Interesting; what's the associated route knowledge level? Taking the OP's wrong routed TGV, the driver has no indication of the route being offered but would stil be expected to identify that something is 'off' with the speed?

 

[hexagon789]

Interesting; what's the associated route knowledge level? Taking the OP's wrong routed TGV, the driver has no indication of the route being offered but would stil be expected to identify that something is 'off' with the speed?

That wouldn't always work though, there are some junctions on the LGVs with equal diverging speeds.

 

[Austriantrain]

That wouldn't always work though, there are some junctions on the LGVs with equal diverging speeds.

Is that even the case here? Coming from Nimes, the route to Avignon is the divergent one, so with lower speed. But running on towards Lyon, where the tracks from Avignon and Nimes join, the Nimes route will - I suppose - have the slower speed. So it might very well be that the train would have had to slow to the same speed on both routes.

 

[hexagon789]

Is that even the case here? Coming from Nimes, the route to Avignon is the divergent one, so with lower speed. But running on towards Lyon, where the tracks from Avignon and Nimes join, the Nimes route will - I suppose - have the slower speed. So it might very well be that the train would have had to slow to the same speed on both routes.

I meant that such an assumption couldn't be relied upon generally, as it wouldn't always be so.

 

[Wychwood93]

'Open Railway Map' shows the route to Avignon to be 170 kph and the route towards Lyon 220

OpenRailwayMap

OpenRailwayMap - An OpenStreetMap-based project for creating a map of the world's railway infrastructure.

www.openrailwaymap.org

 

[Re 4/4]

I suspect such restrictions are rarer on the Continent than in the UK, but probably exist somewhere.

They also exist in Switzerland for trains with "Simplon Inter Modal" loading gauge, that is trains carrying lorries. The route over the Lötschberg has (or had) special route signalling aspects installed in addition to the usual speed signalling.

 

[class ep-09]

deleted

 

[Austriantrain]

They also exist in Switzerland for trains with "Simplon Inter Modal" loading gauge, that is trains carrying lorries. The route over the Lötschberg has (or had) special route signalling aspects installed in addition to the usual speed signalling.

In addition, there are routes in many countries where double-deck stock is not allowed. In Austria, the Semmering e.g. On some others subject to restrictions (e.g. one track only on a double-track line).

 

[DanielB]

The Netherlands also has lines with restrictions for certain locomotives, for example class 1700 which is not allowed between Woerden and Alphen a/d Rijn due to the peaty soil. But that's not enforced by special signals.

There are however special signals only applicable for cargo trains on top of the usual speed signalling. These are mostly used around steep slopes at bridge entrances (giving heavy trains a stop order before the slope instead of on the slope) and around steep descents in tunnels (reducing the entrance speed to avoid overspeed at the bottom of the tunnel due to the train weight).

 

[MarcVD]

Finally found a picture of a belgian signal with direction indicator on it.

 

[Bemined]

The Netherlands also has lines with restrictions for certain locomotives, for example class 1700 which is not allowed between Woerden and Alphen a/d Rijn due to the peaty soil. But that's not enforced by special signals.

Actually there are route signals in the Netherlands, but they aren't being used anymore. They are still included in the regulations though (signal RS 252) but the internal design rules state 'not used anymore in new situations, existing signals must be removed during the next project'.

 

[jamieP]

As far as I know, there isn't any. TGV SNCF is entirely a speed-signalling affair. And I don't believe there is anything foreseen for that in ETCS either.

Im 95% sure the display in the cab does show what the route ahead is set for. Having seen some of the training videos on 700s.

 

[rheingold103]

Im 95% sure the display in the cab does show what the route ahead is set for. Having seen some of the training videos on 700s.

ETCS shows the driver the speed profile of the route ahead that is set. The driver can infer route set where there is a clear difference in speed of straight and diverging routes. The tricky part comes where forward routes are equal speed or where there is a temporary speed restriction that masks the normal profile.

 

[jamieP]

ETCS shows the driver the speed profile of the route ahead that is set. The driver can infer route set where there is a clear difference in speed of straight and diverging routes. The tricky part comes where forward routes are equal speed or where there is a temporary speed restriction that masks the normal profile.

I will rewatch when back at work as im sure it showed junction indicatons.

 

[MarcVD]

Im 95% sure the display in the cab does show what the route ahead is set for. Having seen some of the training videos on 700s.

The TVM 300 and TVM 430 protocols do not have any provision for that. It can just transmit applicable and expected speed limits, plus some punctual indications like lowering pantographs. And the very limited (1970s technology, remember) display capabilities on the driver's desk don't allow anything like that either.

 

[hexagon789]

The TVM 300 and TVM 430 protocols do not have any provision for that. It can just transmit applicable and expected speed limits, plus some punctual indications like lowering pantographs. And the very limited (1970s technology, remember) display capabilities on the driver's desk don't allow anything like that either.

I think jamieP is referring to ETCS though.