Dawlish diversions

In February, part of the railway line at Dawlish was destroyed by the sea. Some heroic work by Network Rail and its contractors saw the line reopen in April at a cost (to the railway) of £40 to 45 million. However that work left longer-term questions about the viability of the coastal route, especially if sea levels rise as expected.

Campaigners favoured various options:

• Reopening the Teign Valley branch. This was a heavily-graded, single-track line, most of which was closed in the 1960s after fluvial flooding.
• Reopening Tavistock to Okehampton. This LSWR line skirted around the north of Dartmoor. A large branch was until recently open to Okehampton to serve a quarry at Meldon. Reopening this line would open up large areas of North Devon to rail services, but would not be ideal operationally due to time-consuming reversals at Exeter and Plymouth.
• Tunnel under Dawlish and Teignmouth to avoid the sea wall. I have previously written about the GWR's pre-war proposals to tunnel under the hills inland, avoiding the tidal and estuarine sections. There are several options for the route.

Network Rail have now released an initial study into these alternatives, and it does not make pleasant reading for people supporting any of these proposals. The government compare planned infrastructure improvements by something called the Benefit-Cost Ratio (BCR). This is a calculation of the return on every pound invested over a period - in this case, sixty years. A BCR of two or above is seen as very good, and represents two pounds back for every pound invested.

It should be said that calculating BCR is an imprecise art: working out the benefits of a scheme and allocating monetary values to them is difficult at best. But as long as the BCR is calculated in the same way, then it provides a reasonable means of comparing projects.

The Network Rail study shows that the BCR for the alternatives range from 0.08 to 0.29. Unless flaws can be found in the BCR calculations, these schemes are absolute non-starters. These flaws might be factors such as wider social and economic benefits, which are not currently included in the calculations. If the BCR figures are unchanged, then investment in such schemes would have to be made on an emotional, rather than financial, footing.

Therefore it looks likely that the existing route will be hardened against the sea. This too is costly, but is very much a known quantity and has the best BCR. Personally I view this as a shame as I favoured the tunnelling option, but if it is not economic, fair enough.

If the government and Network Rail are sensible, they may throw some extra money at improving the rest of the rail routes into Devon and Cornwall. For instance, a significant cause of loss of time is not at the place the line got breached, but on the South Devon banks, which include the third, fourth and seventh steepest inclines on Britain's main line railways. Whilst the gradients can not be improved, there are many things that can be done to improve journey times.

Cornwall is amongst the poorest regions in the UK, and perhaps improving the rail line into the southwest would be a step towards changing that.