NR SSI8003-65B ISSUE 7 PDF

Introduction

Where the overlap from a signal extends over one or more sets of points, the trailing points in the overlap are locked but the facing points are not locked so long as there is a valid overlap over the points in both directions. This allows the points to be moved to swing the overlap when other routes are set in the area. Providing for this additional flexibility adds to the complexity of the geographic data in a number of areas. This document sets out the basic rules for the preparation of data for swinging overlaps, based on Signalling Principles Standard GK/RT0060 [1] and current practice. It also gives examples of the data for varying complexities of layouts with one or two facing points in the overlap.

In this chapter, Section 2 sets out the principles and Sections 3 & 4 give the data techniques for simpler examples.

In Chapter C, Section 1 & 2 give the data techniques for more complicated examples.

In Chapter D:

• Section 1 provides alternative data techniques, mainly for where data processing times are a problem.

• Section 2 provides for preferred overlaps.

• Section 3 provides for Non-Permitted Overlaps, i.e. where overlaps are not allowed to be set through one direction of facing points.

• Section 4 covers the special checks which are required when using Alternative Execution Clauses in the swinging overlap application.

• Section 5 covers Route-selective Restriction on Overlap Swinging, i.e. where route setting swings an existing overlap onto a further set of facing points, and one position of the overlap through these points may conflict with the route being set.

Chapter E includes various additional data methods for setting and swinging overlaps that expand on that shown in the earlier Chapters:

• Section 1 addresses the setting and swinging of parallel overlaps, whether by points key, forward flank route setting or other overlap setting.

• Section 2 expands on methods of swinging overlaps onto further facing points.

• Section 3 provides methods of dealing with potentially opposing overlaps.

• Section 4 covers the swinging of combinations of full and restricted overlaps.

• Section 5 covers swinging overlaps across boundaries.

• Section 6 covers swinging overlaps through a crossover with split detection.

• Section 7 covers optionally track locking overlap hinge points in the event of a SPAD.