‘Shrinking embankment’ services restored

Services on the West of England line between Salisbury and Exeter are being restored from November 15, following months of disruption.

Clay embankments had shrunk during the driest summer since 1936, causing tracks to become uneven (RAIL 965).

Network Rail imposed a speed restriction of 40mph between Tisbury and Gillingham in August. A further speed restriction was in place near Axminster.

NR said that repairs were futile until the shrinking stopped in late October, until rainfall returned to normal levels and the embankment stabilised sufficiently for the track to be realigned.

It meant that South Western Railway’s Class 159 diesels could only run at half the normal speed along much of the route.

And because this is a busy single-track line with limited passing places, each slow train also forced every service in the opposite direction to run late as well.

SWR’s solution was to reduce Exeter to just a two-hourly service, with one train an hour to Yeovil.

The Salisbury to Exeter Rail Users Group (SERUG) said it reduced the average speed on the long-distance route to only 32mph.

SERUG said the route has been starved of infrastructure improvements for over ten years, with just minimum maintenance. It said service reliability is now the worst in living memory and that over the summer, services hit the on-time performance measure on just three days out of 60.

NR’s Wessex Route Director Mark Killick said: “We’re still suffering the after-effects of a record-breaking summer on our railway. We’ve invested tens of millions of pounds on the West of England line in the last two years by strengthening railway cuttings and renewing track and switches and crossings.”

Shrinkage in dry weather does not happen uniformly. Trees and shrubs draw different amounts of water from the ground, and areas exposed to unbroken sunlight perform differently to soil in the shade. Researchers have found shrinkage of more than 100mm beneath the track.

There are 6,000 clay embankments in the Southern region of Network Rail, extending to around 600 miles. The four-mile section near Tisbury is among the longest.

In August, NR told RAIL that a permanent fix to make the region resilient to climate change would cost £15 billion-£20bn and take decades. It said the number was so large, it could never happen.

The return to full service from November 15 will be brief. A further week-long engineering blockade of the line is due on December 10-18, when services between Salisbury and Exeter will be diverted via Westbury.