Over in Northern Ireland, very quietly, something quite remarkable is happening: for the past 18 months, Northern Ireland Railways have been running an hourly service on a single-track mainline with only a handful of passing places. This makes it the busiest entirely single-track mainline in the United Kingdom. While home in Northern Ireland this Christmas, I decided to investigate how this feat of timetabling actually works in practice.
The mainline in question is that running north out of Belfast, through Antrim, Ballymena and Coleraine and onwards to Northern Ireland's second city, known to one side as Londonderry and the other as Derry. (There's an entire Wikipedia article on the naming dispute, if you really want to know.) For the avoidance of confusion I will call it Londonderry throughout, simply because that's what's printed on the timetable (rather than any assertion of my own political affiliation).
Londonderry, a city of 90,000 people, is out on a limb - some might say a withered arm - of the NI railway network, with journeys from Belfast taking slightly over two hours. One problem is that Londonderry is just 70 miles from Belfast by road, but 95 miles by rail, thanks largely to the railway having to avoid the Sperrin hills of Mid-Ulster by heading first for Ballymena and Coleraine and then hugging the north coast.
Moreover, the rail network in NI suffered severe cuts in the 1950s, and for many years the whole network was run down, with just a basic service provided. While the entire line from Belfast to Ballymena, some 33 miles, was once double-track, now just five miles of double track remain at the Belfast end where the line is shared with trains to and from Larne, with the rest of the line reduced to a single track, with loops for trains to pass each other.
But the 1990s and 2000s saw a revival in fortunes, with reopened lines and stations, and a brand-new bridge over the River Lagan in Belfast, all of which contributed to a significant upsurge in use. This was followed in the late 2000s by a complete replacement of the outdated fleet of 1970s slam-door trains with new, comfortable units built by CAF in Spain. Delivered in two batches in 2005 and 2011, the 43 three-car diesel units have revitalised the network. (The closest comparable trains in England would be the three-car Class 185 Desiro units operated by TransPennine Express.)
This much-needed investment was hard to come by, for a number of reasons. For one, the railways in Northern Ireland are still entirely nationalised. But more importantly, the size and usage of the network is so much smaller even than, say, Scotland that even investment in basic track renewals - which are taken completely for granted in Great Britain - have to be fought for with the government in Northern Ireland.
In other words, the fact that NI Railways secured £64 million for upgrades to the track between Ballymena and Londonderry - even after spending £185 million on new trains - represents a very significant investment in transport in NI. The investment will allow speeds on the line to be upgraded, removing some long-standing speed restrictions. The work between Ballymena and Coleraine was completed in 2013, with the line closing for several months, while the work between Coleraine and Londonderry is due to be completed by 2016.
In particular, the speed improvements have already meant that an hourly service can now run between Belfast and Coleraine, a distance of some 60 miles, with only five miles of double track at the Belfast end and six intermediate passing loops (only four of which are in regular use). Indeed, there are enough passing loops to allow a roughly half-hourly service in rush hours in the peak flow direction, with two extra trains into Belfast in the morning and two out again in the evening.
Most impressively, none of the passing loops on the line between Belfast and Londonderry are longer than half a mile: in other words, they all require one or both trains to come to a stand in order for them to pass. While the line between Salisbury and Exeter, with an hourly service, is largely single-track, there is a 10-mile section of double track at Yeovil, and a three-mile stretch at Axminster, giving some margin for error in running an hourly service. Similarly, the Ipswich-Lowestoft line has some double-track sections to help facilitate its hourly service.
So rather than claiming the line to Londonderry as the busiest single-track mainline, you could well argue that it's the maddest; that it's crazy to try and run even an hourly service on a single-track line with no "dynamic loops" - double-track sections which allow trains to pass on the move, rather than forcing one train to come to a stand - let alone to try and run a half-hourly service in the rush hour.
Indeed, most single-track lines in Great Britain are either short branch lines - such as those in Cornwall - or long lines through rural Wales or Scotland, where there might be only four trains a day. Inter-city services on single-track lines are much rarer, and not that much more frequent: even on, say, Perth-Inverness, the service remains irregular, with a train every 90 minutes or so.
Nonetheless, a single-track line to Londonderry has been sufficient until now - the 62 miles between Ballymena and Londonderry were built as single-track and have remained so ever since. And the fact is that, while some upgrades might be feasible if this were England, the NI railway network is so much smaller that even upgrading any significant length of the line to double track would cost far more money than is available. As a result, NIR have become experts at make-do-and-mend.
However, having achieved an hourly service between Belfast and Coleraine with only some track renewals, they now want to extend the hourly service all the way to Londonderry. To do that, they need an extra passing loop. Beyond Coleraine, there is just one passing loop at Castlerock on the 34-mile line run to Londonderry, and that loop is only six miles from Coleraine. Unfortunately, to get a train from Castlerock to Londonderry and back takes about 75 minutes - making it impossible to run an hourly service.
So part of the £64 million will be spent building an extra passing loop at Bellarena, some seven miles closer to Londonderry, which will permit an hourly service to run, at least in theory: it will certainly be tight to keep everything running to time. Part of the justification for the spending is that it entails the removal of the loop at Castlerock, along with the antequated signalling there - this will mean a reduction in running costs for years to come.
For the time being, until the passing loop at Bellarena is completed, the hourly service from Belfast to Coleraine continues every two hours to Londonderry, and in the other hours the train along a short 6-mile branch from Coleraine to the popular seaside resort of Portrush.
To see how it all runs, I took myself on a day trip to Londonderry and Portrush on the Sunday after Christmas. NI Railways do an excellent "Sunday Day Tracker" ticket, where you can go anywhere on the NI Railways network for just £7 - a fantastic value ticket even by comparison to some of the excellent Day Rangers in England, and even if it were twice the price it would be a bargain. A shame it's only available on Sundays!
I caught the 11:20 service from Belfast Central to Londonderry. About five miles north of Belfast, we diverged from the line to Larne at Bleach Green Junction; just as we did, we passed a train coming the other way, just before we entered the single line towards Antrim. Half an hour after crossing that train, we arrived in Ballymena, where the next hourly service was waiting to pass us. We proceeded to Ballymoney and waited for five minutes for the next train to pass us.
It was clear at this point where the timetable had been fudged ever so slightly: Ballymena and Ballymoney are only about 24 minutes apart, even with a call at the intermediate station of Cullybackey. By adding a few minutes at either end, the timetablers created a repeating hourly pattern, where the line was occupied one way for each half of the hour. This also, helpfully, provides a little bit of slack to minimise the knock-on effect of delays. It certainly seemed to function very smoothly for my journeys north and south: the train north was on time all the way, and the train south was all of a minute late back into Belfast.
The Cambrian line, connecting Shrewsbury in England to Aberystwyth on the west coast of Wales, has long had an aspiration for an hourly service, having suffered for years with a two-hourly service to one of the most important tourist regions in Wales. The infrastructure is now in place for trains to run every hour, with an extra passing loop at Dovey Junction and a dynamic 2-mile double-track section at Welshpool.
Once the rolling stock becomes available it is hoped to have an hourly service at least for the morning and evening rush hour from May 2015. But they could do well to learn from NI Railways in how to run and manage a long single-track line: even the Belfast-Coleraine section proves it's possible to run a reliable hourly service.
What's more, though, is that the line between Coleraine and Londonderry is easily one of the most stunning railway lines in the whole of the British Isles. Upon departing Coleraine, you hug the west bank of the River Bann, which on Sunday was like a millpond, beautifully calm. After gradually edging away from the Bann, we arrive in Castlerock, and then head into a 600-metre long tunnel.
At the other end, you emerge for all of 100 metres into daylight, greeted on the north side by the most stunning rough seas and rocky shores of the north Atlantic coast. And after another 300-metre-long tunnel, you come to Downhill Strand, one of the longest and most stunning beaches in Northern Ireland. With the rough waves still lapping onto the shore, the view is easily a rival to Dawlish (if somewhat shorter) and certainly one of the best in the UK.
Further west, as the north shore becomes less exposed and turns into Lough Foyle, there are thousands of wading birds to be seen. In the background, you can see across the estuary to Malin Head in County Donegal, which, in spite of being the northernmost part of the island of Ireland, is in the Republic of Ireland - and indeed, such is mobile phone coverage in that area that my phone briefly picked up a signal from across the border!
It's easily been a decade since I was on the line to Londonderry, and I'd honestly forgotten quite how stunningly beautiful the line is. Michael Palin went as far to describe the Coleraine-Londonderry line as "one of the most beautiful rail journeys in the world". I look forward to the improved service making it possible for even more people to see the wonderful scenery on this busiest (and maddest) single-track railway line.