I do not promise an absence of any further puns in this piece.

So last Sunday the big news was: we can’t put a bridge over the top of the Beaufort’s Dyke, so sure we’ll just build a tunnel round it.  It’ll only be 25 miles long.

Except…

The Channel Tunnel is 37.92km (23.57 miles) from the English coast under Shakespeare cliff to the French coast at Sangatte.  It takes a further 9.14km (5.68 miles) to reach the tunnel mouth at Eurotunnel UK in Folkestone due to the cliffs, even though Folkestone appears to be more or less at sea level.  On the French side, it only takes 3.26km (just over two miles) to reach daylight at Beussingues for a total nominal length of 50.38km (31.31 miles).

What is different about the North Channel?

Depth

If you avoid Beaufort’s Dyke, the North Channel is still twice as deep as the English channel (have a look at this map and zoom and move around as much as you like.)  That means that you would have to travel at least four miles inland just to reach sea level.

Larne is at sea level.  Sounds easy – except that Larne is at the bottom of the Inver valley, and the existing single track railway line hugs the coast round to Kilroot.  More than a few readers might have had their photograph taken on the way down the hill from the Antiville roundabout, which is rather close to the 250ft contour.  So double your distance again.

Travelling up the Inver Valley beside the A8, there is little chance of reaching daylight in NI much before Ballynure.

Getting into Belfast

The geographical constraints are considerable.  The M2 cuts up between Cavehill and Carnmoney Hill, and is at too steep a gradient for a railway line.  The other side of Carnmoney Hill is already occupied by the railway line from Antrim to Bleach Green.

There are three options.

1. Add a third rail to the existing railway line from Kingsbog Junction (the old junction for Ballyclare)
2. Regauage the existing NIR and Irish rail networks
3. Of course, the tunnel could keep going – after all, what’s another 12 miles between friends?

Third rail

Add a third rail.  It sounds easy.  You could reinstate the second track between Monkstown and Antrim as well.

But it isn’t that simple.  Every platform on NIR’s network has been aligned for the centre of the carriages’ bogies to be in the middle of the track.  Even if you added the third rail on the side away from the platform, you would have to replace every sleeper with one capable of carrying two rails at one end with contact surfaces 6 inches apart, which, to put it politely, is tight.  BS113a flat bottomed rail, which is the main rail used by NIR, is 139.7mm wide, against a difference in gauge of 165mm – leaving only 26.3mm to fix the inside of the two rails to the sleeper, with doubts about whether that would be enough to secure the rails against the forces of trains travelling at high speed.

So you overcome that somehow or other (a fourth rail isn’t as ridiculous as it sounds to get adequate spacing between rails), and then you have to consider whether that would leave trains passing each other at too close proximity – in other words, whether the horizontally offset train would still fit within NIR’s existing loading gauge.

As built, incidentally, the answer is yes it probably would have done.  The problem then arises that the train would be at an unacceptable distance for the platform it would serve.

But you’ve just reduced the capacity of the NIR network which is already bursting with commuters in normal times, and in a not entirely dissimilar fashion to trains around Dublin, the notion of a high speed train from Stranraer to Belfast becomes that little bit more ridiculous.

Standard gauge conversion

So convert the NIR network to standard gauge. Through trains Stranraer to… milepost 59.5 between Dundalk and Newry.  Would Irish Rail convert their network to standard gauge as has been suggested?  Frankly, both DfI and the Irish Department for Transport have better things to do than replace every piece of track outside Downpatrick, Whitehead Excursion and Cultra with standard gauge, replace every carriage bogie with a standard gauge bogie (incidentally the easy part of the job) and get GM to build new bogies for all the operational diesel locomotives in Ireland.  An incredible waste of public money that is needed to do everything else, including maintaining and extending the present network.

Plus the effect on preservation.  Are RPSI’s steam locomotives capable of being regauged to 4’8.5″ or are their frames too wide?  Do they have better things to spend money on?

Continue the tunnel

Forget about connecting into NIR’s network.  Run a separate line underground into Belfast and bring it out… where?  The tunnel mouth would have to be convenient to a Le Shuttle-style freight terminal, and the passenger terminal would have to be right beside an NIR station with regular services.

Well, let’s suppose for these purposes that two platforms at Lanyon Place were chosen as the Belfast passenger terminal.  How does the train get there from the tunnel mouth with the intense development around the existing railway lines?

Indeed, how does the proposed high speed link reach either Weaver’s Cross or Lanyon Place at all?  Would the ground conditions allow a new line to be built underground?

Under and round

Ok, so a link to NI is, to be generous, difficult.  What happens on the Scottish side?

Once upon a long ago, a very rich lady needed a new chauffeur.  Three applicants came to meet her at the appointed place, and she showed them the mountain track to her house with its sheer drop on one side.  She asked the first one, “How close could you drive to the edge of that road safely up to my estate?”

“I will take you within 5 inches of the edge safely!”

Not to be outdone, the second applicant said “I will take you within one inch of the edge safely!”

The third one said “Madam, I wouldn’t take you anywhere near the edge of that track.  I would drive as close as possible to the other side of the track in order to keep you safe.”

I wonder who got the job?

It’s the same with Beaufort’s Dyke.  The intention is apparently to skirt around the edge of the dyke – never mind that not all of the munitions are in the dyke.  There are sufficient in and around the dyke to require a proper diversion to maintain safety, and bearing in mind local geography, making landfall as far north as Troon is not implausible, nowhere near the old Port Road.  Even with landfall at Stranraer (if even half practical) the closed railway line from Challoch Junction to Dumfries was steeply graded single track, making a double track high speed line… an interesting prospect.

Conclusion

It’s a dead cat.  Any report discussing its feasibility written by a competent engineer will be delayed until Boris has been removed as Prime Minister, and his successor will quietly forget it. Don’t get me wrong, if it didn’t have all the logistical issues, it would be fantastic for Northern Ireland.

However, in the meantime, it’s another distraction which will do nothing to serve Northern Ireland.