Channel tunnel capacity

[sjoh]

It's oft mentioned that there is capacity in the tunnel for additional services - i.e the aborted DB ICE service to Germany.
But what is the capacity limit, hypothetically?

How many paths are there in an hour (taking into account the obvious restrictions of running the slower shuttle services with the high speed Eurostar services)?
How many are actually used?

 

[jon0844]

I assumed Eurostar slowed to help keep with the other traffic, and thus increase the number of paths?

 

[pdeaves]

I assumed Eurostar slowed to help keep with the other traffic, and thus increase the number of paths?

That's correct, it effectively makes a 'metro' service with everything running at the same speed throughout, giving maximum available paths.

 

[sjoh]

Well, I know it definitely slows from 186mph because there'd need to be a speed restriction in the tunnel to account for air pressure/piston effect etc.
A quick google tells me that it is in fact 100mph* (hadn't realised that Eurostar slowed right down to shuttle speeds), so I guess that makes it easier to figure out. Still not sure where I'd start though.

*well, 99mph cause of km/h rounding.

 

[jon0844]

*well, 99mph cause of km/h rounding.

Damn EU and the metric system slowing down our British trains....

(Don't bother to point all the mistakes in what I've just written!).

 

[daikilo]

Well, I know it definitely slows from 186mph because there'd need to be a speed restriction in the tunnel to account for air pressure/piston effect etc.
A quick google tells me that it is in fact 100mph* (hadn't realised that Eurostar slowed right down to shuttle speeds), so I guess that makes it easier to figure out. Still not sure where I'd start though.

*well, 99mph cause of km/h rounding.

As far as I am aware, 160kph is the maximum allowable speed and is the one used by the Eurostar and maybe the passenger shuttles. Classic freights are limited to their normal linespeed of 120kph; don't know about the freight shuttles.

 

[Chris125]

I was under the impression that Eurostar services operate at a higher speed through the tunnel, so are 'flighted' together to maximise capacity.

 

[MarkyT]

According to Wikipedia, the shuttle locomotives and presumably their trailers, are all capable of 160 kph. The maximum speed in the tunnel is also 160 kph, which clearly Eurostars are restricted to for their passage. Conventional freight is rather slower than that.

Eurotunnel's annual statement document here:
http://www.eurotunnelgroup.com/uplo...usiness/2017-Eurotunnel-Network-Statement.pdf

states:

3.12 Operating Speed
For best use of Channel Fixed Link capacity, the recommended operating speeds are 140km/h to 160km/h for passenger trains, and 120 km/h to 140 km/h for freight trains (wagons capable of 100km/h operation are also accepted, see section 4 below).

The similar new Alptransit tunnels in Switzerland also have a compromise speed capability, both to limit the cost of construction and to maximise capacity for the traffic mix which is intended to be highly freight dominated.

 

[gsnedders]

I was under the impression that Eurostar services operate at a higher speed through the tunnel, so are 'flighted' together to maximise capacity.

This was originally the case; the shuttle originally ran at 140 km/h, but is no longer true. I have no idea why they originally ran at 140 km/h: all the stock was designed for 160 km/h operation—acceleration, perhaps, and then it becoming more common after the Class 9s were upgraded to 7MW?

 

[MarkyT]

This was originally the case; the shuttle originally ran at 140 km/h, but is no longer true. I have no idea why they originally ran at 140 km/h: all the stock was designed for 160 km/h operation—acceleration, perhaps, and then it becoming more common after the Class 9s were upgraded to 7MW?

I imagine a fully loaded freight shuttle starting from rest at the terminal would take a while to get up to full speed, while a Eurostar can enter at full tunnel speed from the high speed connections at either end. It would definitely affect the relative total transit times even if eventually the shuttle got up to full speed. The gradients should help with acceleration and I remember that after the initial batch Eurotunnel ordered some more powerful locomotives for the freights.

Around the time of opening, I remember seeing train graphs in railway press articles illustrating how the different speed paths were interleaved.

 

[gsnedders]

I imagine a fully loaded freight shuttle starting from rest at the terminal would take a while to get up to full speed, while a Eurostar can enter at full tunnel speed from the high speed connections at either end. It would definitely affect the relative total transit times even if eventually the shuttle got up to full speed. The gradients should help with acceleration and I remember that after the initial batch Eurotunnel ordered some more powerful locomotives for the freights.

Around the time of opening, I remember seeing train graphs in railway press articles illustrating how the different speed paths were interleaved.

Many of the original Eurotunnel Class 9s have been upgraded from 5.6MW to 7MW, too: the majority of Class 9s are 7MW ones now.

 

[Bald Rick]

When the tunnel opened capacity was based on the number of standard shuttle train paths used.

The (then) quicker Eurostars used three shuttle paths, whilst conventional freight used two shuttle paths IIRC. This is why the Eurostars are flighted, as 2 consecutive Eurostars use only 4 shuttle paths (in theory).

The main constraint on tunnel capacity is the time it takes for a full length shuttle to clear the Cheriton terminal so that the next one can be routed to follow.

 

[Ianno87]

The 'Standard' Eurostar paths correspond to St Pancras departure times of 01, 04, 31 and 34 minutes past the hour (not all used each hour, of course), based on running non-stop to the tunnel. The 01/31 paths head to Paris, whilst the 04/34 paths head to Brussels. Mirror image in opposite direction. These paths also fit into the LGV Nord standard timetable pattern.

This is partly why on Brussels trains call at Calais and Lille - they can do so, whereas the Paris paths cannot without impeding the Brussels path that follows all the way to Bifurcation de Fretin.

For Eurostars that call at Ebbsfleet or Ashford, they just depart St Pancras slightly earlier than the times above, then pick up the standard timings thereafter. E.g. A Paris train calling at Ebbsfleet becomes xx24 instead of xx31 - 7 extra minutes to allow for the call. It is slightly higher for a call at Ashford due to the slow junctions. This aspect doesn't matter, as there is sufficient gap in Southeastern HS services so that an Ashford caller to Paris can depart St Pancras (say) 5 minutes ahead of an Ebbsfleet caller to Brussels. Having both made their stops (the Ashford call in front taking slightly longer), the Ebbsfleet caller will 'catch up' to be the required 3 minutes behind through the tunnel.

This is why Eurostar departures seem randomly scattered throughout the hour - but there is an underlying standard pattern!

 

[Jordeh]

The 'Standard' Eurostar paths correspond to St Pancras departure times of 01, 04, 31 and 34 minutes past the hour (not all used each hour, of course), based on running non-stop to the tunnel. The 01/31 paths head to Paris, whilst the 04/34 paths head to Brussels. Mirror image in opposite direction. These paths also fit into the LGV Nord standard timetable pattern.

This is partly why on Brussels trains call at Calais and Lille - they can do so, whereas the Paris paths cannot without impeding the Brussels path that follows all the way to Bifurcation de Fretin.

For Eurostars that call at Ebbsfleet or Ashford, they just depart St Pancras slightly earlier than the times above, then pick up the standard timings thereafter. E.g. A Paris train calling at Ebbsfleet becomes xx24 instead of xx31 - 7 extra minutes to allow for the call. It is slightly higher for a call at Ashford due to the slow junctions. This aspect doesn't matter, as there is sufficient gap in Southeastern HS services so that an Ashford caller to Paris can depart St Pancras (say) 5 minutes ahead of an Ebbsfleet caller to Brussels. Having both made their stops (the Ashford call in front taking slightly longer), the Ebbsfleet caller will 'catch up' to be the required 3 minutes behind through the tunnel.

This is why Eurostar departures seem randomly scattered throughout the hour - but there is an underlying standard pattern!

Very interesting post, thank-you.

 

[fergusjbend]

Very interesting post, thank-you.

Agreed! Nice to have information, as opposed to opinion, from time to time.

 

[QueensCurve]

It's oft mentioned that there is capacity in the tunnel for additional services - i.e the aborted DB ICE service to Germany.
But what is the capacity limit, hypothetically?

How many paths are there in an hour (taking into account the obvious restrictions of running the slower shuttle services with the high speed Eurostar services)?
How many are actually used?

I read a lot about this during the construction of the Tunnel starting 30y ago but may get it wrong without digging out the documents. Things may also have changed since.

As I recall the speed limit in the tunnel is 160km/h (100mph for Leave voters ) with 150km/h as the intended speed for the shuttles. The freight shuttles may have been slower but I don't recall.

The signalling headways originally envisaged were 2min but downgraded to 3min during development of the scheme. Again this may be false memory.

The tunnel needs a cooling system to remove heat roughly equivalent to the power consumed by the trains underground. The original headway would have required an ice/water slurry system, but a chilled water system was installed because that was adequate given the reduced signalling headway.

Through freight trains were going to consume multiple paths but there has been little demand for them.

I am happy to be corrected if any of the above is wrong or out of date.

 

[misterredmist]

Agreed! Nice to have information, as opposed to opinion, from time to time.

Quite, gives a very good perspective on the planning & operation

good stuff
--- old post above --- --- new post below ---
Thanks to I87 & QC for their very informative posts.