In 2023, Network Rail embarked on signalling works in the Cambridge area at an estimated cost of £200 million. The current Cambridge signalbox was commissioned in 1982. At that time the northern limit was in the vicinity of Waterbeach, and the southern boundary interfaced with Bishop Stortford signalbox. The area also reached a boundary near Royston on the line to Kings Cross. The southern boundary moved north to Elsenham when Stansted airport was provided with a rail link in 1991 and the adjacent signalbox became London Liverpool Street. Much of the remaining equipment is thus over 40 years old, although some interlockings on this stretch have been replaced by interfaced SSI due to poor condition of the original interlocking wiring.
North of Cambridge, the signalbox control area was extended to include Ely and the route from Ely through Soham in the early 1990s when SSI was installed and the area rationalised. That equipment is now 30 years old. Finally, control of the line from Ely toward Norwich was transferred in the early 2010’s as part of a modular signalling project. The project thus has a number of strands with parts resignalled, others relocked and finally some elements recontrolled. Hence the project title C3R meaning Cambridge Resignalling, Relock and Recontrol.
The need for resignalling is driven by the age and approaching obsolescence of parts of the system and will thus improve reliability and release selected critical spares for other places.
The final control area is illustrated in Figure 1 together with an indication of the original signalling.
The scheme
The main parts of the scheme are as follows:
- The resignalling of the Cambridge station area and south to between Shelford and Whittlesford with recontrol south from there.
- Resignalling of the route from Cambridge via Newmarket and Bury St. Edmunds resulting in the closure of three mechanical signalboxes.
- Relocking by provision of new computer based interlockings and the provision of a new VDU based control system within the current Cambridge signalbox structure.
- The route from Ely north junction to Wymondham will be recontrolled on to new workstations compatible with those used for the rest of the control area.
Overall, the new centre will cover approximately 132 track miles. Associated works will be carried out at a number of level crossings, with seven upgraded due to safety concerns. There are also enhancements to the telecommunications network and power supply systems that support the signalling. In excess of 600 Signalling Equivalent Units (SEU) will be updated as part of the project.
The area around Cambridge is also subject to four other extant or potential projects that require alteration to the signalling, including:
- The building of Cambridge South station which is substantially complete and expected to open during 2026.
- Plans to relocate and expand Waterbeach station between Cambridge and Ely as part of a wider expansion of the town.
- The Ely Area Capacity Enhancement scheme, currently awaiting decision.
- The longer-term effect of East West Rail on capability requirements around Cambridge.
The resignalling includes alterations for Cambridge South and ensures there is capacity to add or amend the signalling to cope with the other schemes when or if they are developed.
Alstom was awarded the contract for the work in February 2022. The firm has designed and built the new interlockings around the Smartlock 400 system using its new object controller Smart I/O. All replacement interlockings will be located in Cambridge signalbox. Communication between the new interlockings and the object controllers is via internet protocol communications links over fibre using Network Rail FTNx services.
The signallers will use a new VDU based Modular Control System (MCS Infinity) supported by Modular Automatic Route Setting (MARS). Train detection will use Frauscher axle counters. Within the resignalled area some of the level crossing control systems are being updated using ElectrologIXS controllers. Signals are being converted to LED aspects, where suitable, using the Dorman light weight LED signal. Where the condition of the signal support is not considered serviceable the signals are being renewed.
Level crossings
An additional part of the scheme is a change to the operation of seven level crossings seen as having significant safety risk, or as a result of the abolition of the adjacent controlling signalbox. Six of the level crossings are being converted to Full Barrier Obstacle Detector level crossings and one to CCTV. The crossing at Dullingham is converted from manually controlled gates (MCG) to an obstacle detector crossing due to the closure of the current adjacent signalbox. Those at Croxton, Six Mile Bottom, Dimmocks Cote, Waterbeach, and Milton Fen are similarly converted from Automatic Half Barrier (AHB) to Obstacle Detector, while one at Meldreth Road will be converted to CCTV.
While not being changed from an operational perspective, the crossing at Hauxton Road, Little Shelford will have the new control equipment housed in a new Relocatable Equipment Building (REB).
In addition to the crossings being upgraded are several others in the control area, in particular five CCTV monitored crossings on the line toward Liverpool Street as well as a significant number of AHB and other crossings. The location of the seven upgraded level crossings is shown in Figure 2.
On the topic of level crossings, that at Foxton remains as a gate box but the control equipment is being renewed. Foxton is a particularly busy crossing with up to six passenger trains in each direction per hour going across the A10 trunk road from London to Cambridge and on to Kings Lynn.
Additional works
Associated works were required to provide suitable cable routes, power supplies, and access to the fibre optic telecommunications network for communications services linking the interlockings and external object controllers. Some of this work has been carried out by subcontractors with Telent charged with providing the necessary access points to the FTNx network. Unipart is assembling the equipment housings and testing them at Waterbeach prior to trackside installation in the majority of cases. AtkinsRéalis is preparing the interlocking data while Baldwin Frances is responsible for creating seven new power supply points for the remote signalling installations.
The Smartlock 400 interlockings will drive the external equipment via 49 equipment housings distributed along the route. Each housing comprises a Smart IO system driving the signals and points in the local area and house the Frauscher axle counter evaluation units. The interlockings located in Cambridge signalbox will communicate with the Smart IO using internet protocols over the Network Rail FTNx network with diverse routing facilities. Except where possession constraints dictate, these housings are being fully equipped by Unipart at the Waterbeach site office, tested and then subject to a soak trial to eliminate as many early failures as possible prior to installation.
The final installation will be operated from six workstations. The first workstations (Workstations 3 and 4) were commissioned during the Christmas period of 2024. These control the area north from Waterbeach up to and including Ely. This area was relocked rather than resignalled meaning a new interlocking was provided but much of the outside equipment has been reused. This work decommissioned part of the old Cambridge signalbox NX control panel which has subsequently been removed.
During a blockade over the Christmas 2025 period, the main resignalling south from and including the Cambridge station area was completed and Workstations 1 and 2 were brought in to use. During this period the remainder of the control panel was decommissioned and subsequently removed. This coincided with the final major construction stages for Cambridge South station, thus minimising temporary stage works. The station is currently expected to open during 2026.
In summary
The Cambridge area resignalling work affected over 100 signals, 76 point machines, and over 300 axle counter sections, and provided 323 signalled routes controlled from two new interlockings. In addition, there were nine level crossing recontrols and the recontrol of the SSI and RRI interlockings south of Whittlesford.
The new Workstation 1 supervises the area from Cambridge South station to the southern boundaries of the signalbox at Elsenham and approaching Royston. Workstation 2 supervises from the northern end of Cambridge South through to just beyond Coldham Junction and the line to Newmarket that is the area of Cambridge station. The work over Christmas was completed successfully and is now in daily service.
Stage 3 includes most of the level crossing works and recontrol of the Ely to Norwich route on to workstation 6 during 2026, while Stage 4 brings control of the Newmarket and Bury St. Edmunds resignalling in to use on Workstation 5 in 2027.
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