scope:

All planned changes, whether temporary or permanent, shall be carried out in accordance with this standard. Urgent unplanned temporary changes (to provide service in the event of failure conditions) will normally be carried out in accordance with E7502, Irregular adjustments to the signalling system, but may be carried out in accordance with E7501 if all its requirements can be met.

The requirements of this standard generally do not apply to exact like-for-like substitution of components, but may apply (in whole or in part) if extensive and simultaneous like-for-like replacement or reinstatement is planned, even where this does not depart from the existing design drawings. The Professional Head of Signalling should be consulted for guidance in such cases.

This standard shall not apply to any train carried elements, but shall apply to:

a) any interfaces (such as power supplies, arrestors or point heaters) whose alteration might directly affect the safe operation of the signalling;

b) any integrity monitoring or enhancing features of the vital system.

This standard does not address the safety assurance or design approval process required for new types of equipment, or the detailed planning and documentation of testing.

The key requirements of this standard are:

a) confirmation of the existing „as built‟ records before making any physical change;

b) formal definition of the change by means of authorised drawings or documents;

c) the controlled release (or „issue‟) of these documents by the Application Design Authority;

d) planning the execution of the work;

e) authorisation and certification of the physical task;

f) physical „proving‟ of the changes as they are made;

g) independent principles test of any change;

h) updating of records;

i) personal competence (licensing).

While this standard is written primarily around the requirements for hard-wired systems, the spirit of the standard shall also be applied to data driven and other software based systems where this is appropriate. The requirements should also be used as a checklist when planning the alteration of control systems.

The expected users of this standard are all persons responsible for the procurement, planning, design, installation or commissioning of alterations to the Signalling System.

Purpose

This standard defines the requirements that must be followed when making any planned physical change to the vital signalling system for which LU is the Infrastructure Manager where that change involves either:

a) a departure from the existing design, or

b) a change of component type or version.

In this document the terms „alteration‟ and „change‟ are equivalent, and mean any departure from the existing design, either in respect of component types or versions, or in their electrical or mechanical arrangement (as detailed in section 3.5).