Due to the complexity of the interfaces between the systems, many of these changes needed to be conducted concurrently in order to function, e.g. the new PIS would not interoperate with the old DTS.
Each project had its own defined goals, but the complex array of interfaces and the requirement for all systems to be installed at the same time, pulled these projects into a programme with overarching goals of improved reliability, accessibility, and passenger security and safety.
Each project had a project team, and a programme management structure to bring cohesion between the projects. A systems engineer was recruited into the operator’s project office for this programme to deliver the integration of these six systems/projects/contracts. The systems engineering included integration of the six systems with each other, of each system with the existing rolling stock and with ongoing maintenance activities / projects. The systems engineer introduced multiple systems engineering processes to manage the complexities of this programme.
Prior to CLIP, the Central line rolling stock had four configurations of vehicle: motor car with cab (type A), a motor car (C) which is similar to an A car but with shunting controls in lieu of a cab, both of which are permanently coupled to a non-driving motor car (B). Some C cars have equipment for de-icing the conductor rails (D). CLIP introduced a fifth: a B car with wheelchair space. Each configuration required its own design, resulting in additional complexity to the interface management.
On top of this, some of the new systems could not interoperate with their predecessor system. Where systems were limited to communications within a single car, this had minimal impact but where communications required connection into the train-level communications system, this had the result that modified cars could only be coupled into a train of modified cars, and the same for unmodified cars.
By developing an architecture description, the development of the designs and the interfaces was monitored not only on a system-by-system basis, but a configuration-by-configuration basis. In early design stages, suppliers would simplify the architecture by broadly referring to two car types (motor (A car) and non-driving motor (B car)). Monitoring of the configuration developments and interface management performed by the systems engineer encouraged suppliers to develop designs for the five configurations in an earlier stage and mitigate risks that would have otherwise been realised at prototyping (for example, by trying to fit a piece of equipment in a place where de-icing equipment is already mounted).
The architecture description was made up of five sheets (one for each car configuration) and depicted the design development of each, by bringing together submitted design documentation from each of the suppliers. As well as showing how the designs were being developed, and how space was being allocated on the cars, this also highlighted how design maturity differed between the systems, which was critical for understanding the risk associated with design changes.
The development and maintenance of an architecture description allowed for effective configuration management throughout the design and prototyping phases. Effective management of this phase saves cost; failure to do so causes the programme to be extended leading to significant extra cost.
Each replacement train-borne system has interfaces that fall into three categories:
1. Interfaces with existing and unchanged systems
2. Interfaces with replacement systems
3. New interfaces with new functionality
For example, amongst others, the PIS has the following three interfaces:
1. Passenger Emergency Alarms – this interfacing system is unchanged and so can be specified and designed against in order to retain existing functionality
2. DTS – this interfacing system is being replaced, so the PIS and DTS interface specifications and designs are developed in parallel by the respective suppliers, such that existing functionality is retained
3. Saloon CCTV – this interfacing system is new, so the specifications and designs are developed in parallel by the respective suppliers, but new functionality also needs to be specified