Home Rail News Cornwall’s Capacity Triumph

Cornwall’s Capacity Triumph

Listen to this article

Back in January 2018 (issue 159), Rail Engineer reported on a plan to increase the capacity of rail operations in Cornwall by upgrading and modernising the existing signalling. At that time, the plans were almost finalised but work had yet to start.

A subsequent article in October 2018 (issue 168) described the data communication links associated with the scheme and how these were enabling the signalling to be interconnected.

The project work was completed by October 2018 and thus an enhanced train timetable has existed throughout the recent summer. So how has it worked out in practice, what benefits have been realised, does the new technology fit in with the old and have any downsides been noticed?

Rail Engineer spent a day touring the various sites to see the signalling in action and to talk with the people involved.

Project Background

In later BR days, much of the signalling in Cornwall was rationalised, with many boxes being closed and long block sections created. The line from Burngullow (near St Austell) to Probus (just short of Truro) was even singled, which resulted in operating chaos if trains ran late, that could have knock-on effects right across the rail network.

After living with this nightmare for a few years, the section was redoubled, with some intermediate signal sections incorporated between Par and Truro, which perhaps set the scene for what was to come.

For some time, ways to improve Cornwall’s signalling had been under discussion, even including thinking ‘outside the box’ by outsourcing the upgrade and subsequent operation to one of the signalling suppliers. Quickly dismissed as impractical on a number of counts, a revised proposal was investigated to completely re-signal the route with track circuit block, colour light signals and a single control centre. Whilst perfectly possible, it would have been an expensive project and the business case did not stack up. Could there be a more pragmatic solution?

The answer was yes, by retaining the existing signal boxes, shortening the block sections to create around a six-minute headway, modernising some of the level crossings and utilising the recently provided telecom transmission links to join it all up.

Plans reached an advanced stage by the middle of 2017 and two contracts were let, one for the eastern (Amey) and the other for the western (Atkins) sections. These companies would work with Network Rail to design, install and test the new additions, engaging specialist subcontractors as required to supply the necessary component parts.

The eastern section (Plymouth to Lostwithiel) was commissioned in three stages during the Spring of 2018 and the western section in a single stage by means of a short blockade in Autumn 2018. Using the winter of 2018/9 to bed the systems in, an improved timetable has been in place during the summer and a further timetable enhancement will take place in December 2019.

Signal boxes and the control

Eight signal boxes remain on Cornwall’s main line – Plymouth Power Signal Box, Liskeard, Lostwithiel, Par, Truro, Roskear, St Erth and Penzance. All these have different characteristics and have needed to be modified in different ways.

Plymouth Power Box.

Taking each in turn:

Plymouth Power Box must be one of the oldest power boxes still in existence, having been commissioned in November 1960. Although extended in operation both eastwards and westwards, it remains the same basic equipment with the former Western Region ‘push and turn’ button route setting. By careful manipulation of the panel tiles, the extensions have been accommodated within the same panel framework.

The latest work has been to provide an additional signal section of home and distant signals on both lines at Menheniot between St Germans (the original fringe point) and Liskeard. At the same time, the existing Alcatel 70/30 type axle counters have been replaced with the current Thales K type, these being more reliable and enabling a standard to be set for all of Cornwall.

Henry Williams did the alterations to include the new panel and the changeover was achieved during a night-time period. SPTs (signal post telephones) have been deemed necessary at the new home signals, although the comment was made that these are rarely used – perhaps prompting a general thought as to the continuing necessity of these in general.

Liskeard signal box frame and diagram.

Liskeard is still a mechanical box, with traditional lever frame and lower quadrant signals in the immediate station area. Other than shortening the section towards Plymouth, by moving the last Up signal nearer to the box and thus taking account of the new section at Menheniot, the operation is largely unchanged. Track circuits remain in the station area but axle counters exist for the sections east and west, under the control of Plymouth and Lostwithiel respectively.

A new Train Describer video screen is provided for descriptions from Plymouth, but thereafter it is old-fashioned block bell signals that give details of trains to the west. The headway towards Plymouth has been reduced from 11 to five minutes.

Liskeard is also the junction for the Looe branch line which still sees occasional freight traffic to Moorswater; the operation of this line remains something of an anachronism, see separate boxed article.

Lostwithiel supplementary panel.

Lostwithiel, although it still has a mechanical box for the station area, with track circuits and lower quadrant signals also has had a separate panel since 1991that uses axle counters to control the eastern section up to the single line over two viaducts. This signalling was originally controlled from Largin box, but that eventually had to be closed because it had no running water and was denounced by the environmental authorities. The opportunity was taken at the time, to control the section with an original Mark 1 SSI (solid state interlocking) which, for convenience, was located at Par.

The section to Largin has been further shortened by an additional home and distant signal section at Bodmin Parkway, which also has a ground frame to control access to the Bodmin and Wenford Heritage line. At that station, ‘off’ indicators are provided for train despatch and a white/green banner signal is provided on the down line to improve signal sighting. The SSI has been upgraded and reprogrammed but remains a Mark 1 version. A new panel has been provided by Henry Williams to accommodate the additional signalling and the axle counters have been changed for the more modern K type.

The station at Lostwithiel has no footbridge so passengers have to use the adjacent level crossing to get to an opposite platform. With the increase in rail traffic, the barriers can be down for an extended period, thus leading to some complaints. A new footbridge would be welcome but, mindful of the disabled access regulations, it would be expensive. Anyone know of a second hand one that might be available?

Lostwithiel is also the junction for the freight-only line to Fowey, so dealing with the considerable freight movements has meant keeping the Up and Down loops on the eastern side of the crossing, again lengthening the crossing closure time. The plea was made for more passenger trains to stop at Lostwithiel and perhaps also to restore the passenger service to Fowey.

Par is basically unaltered, being only a short block section from Lostwithiel, with the box retaining mechanical signals and track circuits in the station area. The line to Newquay diverges at this point. New signal sections were introduced at St Austell, Burngullow and Probus when the line was redoubled in 2005 using two-aspect home and distant signals and axle counters, all controlled by a local panel. No further work has been necessary.

Truro frame, block shelf and diagram.

Truro is the busiest box on the line as it controls the half-hourly service on the Falmouth branch line as well as the main line trains, all of which amount to 1,000 lever movements each day. The station area has mechanical signals and track circuits as elsewhere.

The Truro control area extends westwards to include a user-worked crossing (UWC) at Paradise (lovely name) which has been converted to miniature light operation. This has helped eliminate the constant phone calls from users of the crossing, thus easing the signaller’s workload.

To shorten the very long block section westwards to Roskear, additional signal sections have been introduced at Chacewater and Redruth, with home and distant signals and axle counters controlled by Roskear. Truro has a level crossing at the east of the platforms that controls entry to the station car park and some commercial premises. As at Lostwithiel, the barriers can be down for a considerable time, meaning that passengers have insufficient time to park their cars and may catch the intended train. More thought must be given to solving this problem.

Roskear new panel with duty signaller.

Roskear signal box is just to the east of Camborne station and was originally a junction for some local freight lines. The immediate area abounds in level crossings, so the lever frame was abolished some years ago and replaced by switches mounted on the block shelf for the colour light signals and motorised points. With the advent of the eastward two signal sections and another one westward at Gwinear Road, this arrangement was not practical, so a new panel has been provided with a completely new relay-based interlocking. The design of this was carried out by Atkins signal engineers with Unipart Rail providing the panel. The block shelf was raised up during the installation work to facilitate the provision of the panel. Two level crossings are controlled directly, one immediately outside the box, the other at Camborne station, monitored by CCTV.

LiDAR detector at Dolcoath with shutters open.

A further crossing at Dolcoath, to the east but still in the Camborne urban area, was originally an AHB (automatic half-barrier crossing), but misuse and some near misses led to this being converted to a full barrier crossing with obstacle detection. While this has led to longer down times and some complaints, the safety risk has largely been eliminated. The crossing has the usual radar and LiDAR sensors, with the latter having motorised shutters to prevent the ingress of dirt when not needed for sensing purposes.

A number of user-worked crossings are also in the vicinity, all of which have been converted to miniature light operation, with a consequential safety improvement.

From Roskear westwards, after the Gwinear Road signal section, the line reverts to absolute block operation with non-continuous detection of trains. To ensure safe operation, a tail light viewing camera is provided at Camborne so that the signaller can see that the train is complete before giving a line clear bell code back to St Erth. As stated before, no train describer system exists west of Liskeard but TRUST (a nationwide computerised train reporting system) screens are provided here and elsewhere to give signallers an overview of train movements.

St Erth has seen no significant change to the signalling, with mechanical lower-quadrant signals and track circuits retained in the station area, but recent work to upgrade the St Ives branch ‘park and ride’ operation has been introduced for the summer of 2019, see boxed article.

Penzance has also not been changed, so it retains an annoying single-line section into the station throat, which will become a greater nuisance now that the train service is enhanced. A depot maintains the new IEP trains that now operate the London service.


Other than the SSI controlling Largin and Bodmin Parkway, the signalling is all relay-based free wiring, modifications to existing interlockings and the new interlocking at Roskear being designed and implemented by Amey or Atkins under the supervision of Network Rail engineers. The new signal-section signals have been provided by Collis Engineering, using a lightweight structure, with axle counters being the Thales AzLM-K type.

At the new signal sections, the REBs were provided by MGB Signalling and wired off-site before being brought to site by lorry. Power is provided from the domestic mains but with a USB battery providing a 12-hour backup supply. Any power failure is reported back to Swindon control which then takes steps to remedy the problem. If need be, petrol generators can be brought to site should the outage be for an extended time.

Network Rail Telecom’s FTNx data network is the ‘digital pipe’ that links it all together with Siemens Westplex TDM (time-division multiplex) systems borne upon it to control the signalling commands. The IP (internet protocol) networking is carried on Westermo Lynx switches that configure the linkage in a ring formation to give maximum resilience.

Since commissioning, all equipment has performed remarkably well and is maintained by a Network Rail team based in Plymouth.

Level crossings

This article has commented on the numerous level crossings that exist on the Cornwall main line and the longer barrier downtime that occurs with the improved train service. The signaller-controlled crossings adjacent to Lostwithiel, Truro and Roskear boxes, the latter including Camborne by CCTV surveillance, all have to have barriers proved in the lowered position before the protecting signals can be cleared. Signallers commented that, with the shortened sections, they need to get the barriers down in good time to avoid delaying trains.

The OD crossing at Dolcoath similarly requires the barriers to be down and no obstacle detected before the signals can be cleared.

The UWCs, of which there are six in total (three for footpaths, three for access roads), previously required a phone call to the signaller before permission to cross safely could be granted. This could add a significant workload to the signaller, so the provision of red and green crossing lights negates this need. The chosen system is the Schweizer VAMOS product, activated when approaching trains pass over a rail mounted treadle, in this case a Frauscher axle counter suitably adapted.

The UWCs retain unlocked gates, so are still something of a risk where stopping trains at a previous station can cause the red light to show for a much longer time. Ways of overcoming this using a form of approach control are being investigated, but the overall safety is much improved.

As has been mentioned, barrier down times have been lengthened and will increase further as more trains are put into the timetable. This will result in an increase in the number of complaints; one partial solution could be to have a call-on signal where a train is booked to stop at a station platform immediately followed by the crossing. The signaller could then keep the barriers up until the train is ready to re-start.

Finance, benefits and future potential

The project has cost around £30 million. Cornwall Council has contributed £15.1 million (of which £11.9 million was from the European Regional Development Fund) with the remainder funded by the Department for Transport. In monetary terms, this is moderate expenditure and represents good value. The extreme rationalisation of BR days has been reversed by a pragmatic approach. Perhaps more importantly, the impact of almost making this a local scheme, where changes to requirements can be discussed and agreed between the Network Rail project engineering staff and the contractor, has yielded considerable benefits to both time and cost.

OK, the technology is not the latest (some of it remains from the Victorian era) and it is a million miles away from an ETCS-controlled railway, but does it really matter? If the train service provision can be delivered to meet customer requirements and the equipment can be maintained in a reliable condition, then so what?

Thanks to Paul Mundy, the project engineer for the scheme, and to the many signallers for sharing their experiences and opinions.