Chiltern “Gaps”

[O L Leigh]

There are a couple of locations along the Chiltern route where the “6 foot” becomes the “several hundred yards”, and I’ve always wondered why this was.

The first is between Saunderton and Princes Risborough and contains fields and more than one residential property while the second slightly smaller one between Haddenham & Thame Parkway and Bicester North looks like uncultivated scrub.

I can’t imagine that they are there for cost saving purposes, as the need to survey and construct earthworks for two alignments must surely have been more expensive than just building one. So why are they there? Are they the sites of former junctions or does their history have some other explanation?

 

[bramling]

There are a couple of locations along the Chiltern route where the “6 foot” becomes the “several hundred yards”, and I’ve always wondered why this was.

The first is between Saunderton and Princes Risborough and contains fields and more than one residential property while the second slightly smaller one between Haddenham & Thame Parkway and Bicester North looks like uncultivated scrub.

I can’t imagine that they are there for cost saving purposes, as the need to survey and construct earthworks for two alignments must surely have been more expensive than just building one. So why are they there? Are they the sites of former junctions or does their history have some other explanation?

The first is where the up line is a newer alignment including a tunnel, which avoids a summit and what would have been a severe gradient for up trains. The down alignment pre-dates the GW/GC joint line.

The second widening is the site of Ashendon Junction, where the GC route once diverged.

 

[SargeNpton]

At Saunderton, an old OS map suggests that there was another track in between, possibly a junction.

Georeferenced Maps - Map images - National Library of Scotland

maps.nls.uk

 

[swt_passenger]

At Saunderton, an old OS map suggests that there was another track in between, possibly a junction.

Georeferenced Maps - Map images - National Library of Scotland

maps.nls.uk

That central bit between the two tracks on your linked map is the original route, but the down line was also straightened to ease the curve. The NLS 25” map shows it in the as built condition:

Side by side georeferenced maps viewer - Map images - National Library of Scotland

maps.nls.uk

 

[Watershed]

There are a couple of locations along the Chiltern route where the “6 foot” becomes the “several hundred yards”, and I’ve always wondered why this was.

The first is between Saunderton and Princes Risborough and contains fields and more than one residential property while the second slightly smaller one between Haddenham & Thame Parkway and Bicester North looks like uncultivated scrub.

I can’t imagine that they are there for cost saving purposes, as the need to survey and construct earthworks for two alignments must surely have been more expensive than just building one. So why are they there? Are they the sites of former junctions or does their history have some other explanation?

The original line to Princes Risborough was a single track, minor branch line, built by the Wycombe Railway. This had a steep gradient of 1:88 as it descended down the Chiltern escarpment. It was built this way to avoid the expense of a tunnel.

When the line was doubled and upgraded by the Great Western and Great Central Joint Railway, between 1900 and 1905, the gradient was deemed too steep for a mainline route, and so a new alignment was built for the Up line. This included a short tunnel, enabling the gradient to be eased to 1:167.

Between Haddenham and Bicester, the alignment of the Up and Down lines again diverges at the former site of Ashendon Junction. This was a fully grade separated junction, akin to Cogload Junction. When the line was redoubled in 1998, the old formation of the Up and Down lines was reinstated.

 

[The Planner]

The original line to Princes Risborough was a single track, minor branch line, built by the Wycombe Railway. This had a steep gradient of 1:88 as it descended down the Chiltern escarpment. It was built this way to avoid the expense of a tunnel.

When the line was doubled and upgraded by the Great Western and Great Central Joint Railway, between 1900 and 1905, the gradient was deemed too steep for a mainline route, and so a new alignment was built for the Up line. This included a short tunnel, enabling the gradient to be eased to 1:167.

Between Haddenham and Bicester, the alignment of the Up and Down lines again diverges at the former site of Ashendon Junction. This was a fully grade separated junction, akin to Cogload Junction. When the line was redoubled in 1998, the old formation of the Up and Down lines was reinstated.

You sure? I thought the up line went over the GCR on a flyover. The current up line is a new formation.

 

[Watershed]

You sure? I thought the up line went over the GCR on a flyover. The current up line is a new formation.

Well, the same alignment even if not the same formation.

 

[Taunton]

When the line was doubled and upgraded by the Great Western and Great Central Joint Railway, between 1900 and 1905, the gradient was deemed too steep for a mainline route, and so a new alignment was built for the Up line. This included a short tunnel, enabling the gradient to be eased to 1:167.

The GWR had a particular penchant for building replacement main lines that embraced onetime branches which had unsuitable bits. The Severn Tunnel English side climbout to Patchway is the same, the London-bound line, opened in the mid-1880s, is on a continuous climbout from the tunnel, whereas the down line is the old Pilning branch with varying gradients, some quite steep, which makes it separated and both well above and well below the opposite line at different places.

The Castle Cary line likewise included various bits of minor branches where the issue was more curves which had to be sorted out later - both Westbury and Frome got bypass lines in the 1930s.

If the replacement alignment between Newton Abbot and Totnes had gone ahead around 1900 it would have been interesting if they would have done one new track, or two.

 

[Pigeon]

I always have a bit of a feeling that it was a shame they never did it at Malvern. Indeed, when I first noticed the old tunnel with its slightly steeper gradient was still there, I thought they actually had done it originally (being already aware of the practice) and it had been BR who then singled it (along with much of the rest of the route). It wasn't until it became possible to look up random guff on this internet thing that I discovered the GWR had considered it but then decided not to.

If the replacement alignment between Newton Abbot and Totnes had gone ahead around 1900 it would have been interesting if they would have done one new track, or two.

Now that's a new one on me which this internet thing doesn't seem to include in its random guff. I've heard of the ideas for building a Dawlish avoider by going round the back, and of course I've heard of the GWR's flurry of cutoff building around the turn of the century, but I'd not heard of any plans for a Dainton avoider just between NA and Totnes.

Thing about Dainton which differs from the other quoted examples is that it's pretty well symmetrical and like the roof of a house on both sides. So you can't get away with building just one new track and saying the state of the old one doesn't matter because we only need it for going downhill now. Unless what they were actually thinking of was of a strange enough nature to counteract this point, I think something resembling Sharnbrook is much more likely.

 

[Taunton]

I've never seen any drawings for the proposed new line west of Newton Abbot, but understood it was an extension of the Dawlish avoiding line project. It was the centrepiece of the long running feud between Grierson, the GWR chief civil engineer, and Churchward. Grierson, on a roll for new lines, put his Dainton proposal to the GWR Board, saying the locomotives could not handle the gradients, the expense of double heading, line congestion, etc. Churchward then said he would design a locomotive that could handle expresses over the hills much cheaper than a big civils project, the board sided with Churchward, who went off and designed the Star. Grierson's project was lost, he was insulted, and the two hardly talked thereafter. Grierson was the son of the GWR General Manager in Victorian times, and probably thought he was set for full support. He did oversee a huge new construction programme, not just the major new lines but a series of shorter jobs avoiding problem points, such as through Cornwall. Some of his projects have given trouble over time - the Badminton line has had several major issues and closures, flooding in Sodbury Tunnel never to this day having been fully overcome.

Dainton is more than a house roof, it's more a lightning bolt, because it's hugely up from Newton Abbot to the summit, equally down to Totnes, then sharply up again to Rattery, onto Dartmoor. My hunch is the proposal overcame all three, which dated from the original Atmospheric Railway alignment, and just in the dip where speed should be maximum both ways there's the sharp curve through Totnes down at River Dart level.

 

[Pigeon]

Thank you for that - most interesting. It has to be said that Churchward's approach was rather more realistic... you could flatten Dainton to any arbitrary degree depending on how long a tunnel you felt like digging, up to about 3 miles (still not exactly a minor project, but not incomparable with Chipping Sodbury tunnel), but this idea doesn't work for Rattery and the route the line takes up there already is not far enough off the optimum to be worth trying to find a better route. That remains the case even if Totnes is approached via a combined Dawlish/Dainton avoider, and as far as I can make out to address all three of those points thoroughly enough to be worthwhile, you'd have to bypass the entire district with a whole new route all the way between roughly Exeter and Ivybridge that would still involve a huge amount of burdensome civil engineering works however you did it, over much more awkward topography than the other whole new routes.

There really aren't any good routes available between Exeter and Plymouth, and although Brunel's route has always been something of a pain it would be hard to come up with much of a better idea for the operating conditions and practices at the time he picked it. It keeps the line as good as possible for as long as possible and then minimises the length of the awkward section, which can't be done any other way, and the need to go "now everybody shuddup, OK, 'cause now comes the verse bit" at Newton Abbot was not anything like the encumbrance it would become later on. The atmospheric system was not first proposed until some months after the route had already been decided, so it can't be blamed on that; the best justification does seem to be that with the land going up and down the way it does round there, any other route would have had a much longer hard-to-operate section and still been no less hard to build.

It's interesting to wonder, if vulcanised rubber had been developed a few years earlier and the atmospheric installation continued rather than discarded, whether they would have considered such a bypass worthwhile somewhere around 30 years earlier. The need to split everything up into very small train loads with a hard limit on total train weight would have become an intolerable bottleneck sooner or later, and with less capable locomotives and depending on how fed up they were with it by then anyway, maybe a complete new route would have looked more attractive.

 

[Mikey C]

That section between the tracks around Saunderton is interesting to walk around!

The Ridgeway National Trail crosses both tracks, the down line via a well used foot crossing, the up line where it's in the tunnel. Indeed if you walk northbound between the tracks, there's another less used foot crossing further north