Principles

Question 1

When are subsidiary signals used?

Answer 1

• Direct Entry to a siding or yard from running line
• Entry into an occupied platform
• Shunting purposes

Question 2

How do you signal a junction indicator when no one route is easily distinguishable as the ‘straight through’ route?

Answer 2

An indicator must then be provided for every route.

Question 3

Why must junction indicators be proven lit before a signal can be cleared over a route?

Answer 3

There are no indicators for an obvious straight through route, so we must prove the driver is getting the indication for the route or they may go through the route at a higher speed assuming they had the straight through route.

Question 4

How many lamps must be proved in a route indicator?

Answer 4

3 of 5 (incandescent)

Question 5

What is approach releasing for?

Answer 5

It is a method of speed signalling, ensuring drivers have slowed enough for the route.

Question 6

If the signal at the end of a block section can be sighted from service braking distance, what can be installed in lieu of an approach signal?

Answer 6

Approach beacon

Question 7

What are the margins of placement for an approach signal or beacon if sighting doesn’t permit placement at braking distance?

Answer 7

-0%, +20%

Question 8

What aspects should an approach signal have at a minimum?

Answer 8

Two aspect Green over Yellow

Question 9

What is the difference between an approach signal and a repeat signal?

Answer 9

• Approach signal physically has a small beacon sign on its signal pole, whereas a repeat signal has a reflectorised “P” plate.
• Approach signal is for the signals at the end of a block section, placed at braking distance for the signal in rear of it.
• Repeat signal is used when visibility of a main signal does not conform to the Signal Positioning Principles and is not placed at braking distance for the signal it is repeating.

Question 10

When is an X indicator used?

Answer 10

When a route is not wired for electric traction and one or more of the approaches is wired.

Question 11

What speed should a DSI show if the next signal is a flashing yellow?

Answer 11

40km/hr

Question 12

What speed should a DSI show if the next signal is an offset yellow?

Answer 12

25km/hr

Question 13

What aspect is used to prevent near-end or far-end conflicts?

Answer 13

Flashing Yellow

Question 14

When is an offset yellow used?

Answer 14

Main routes into passing loops or refuge/track circuited sidings.

Question 15

What does a repeat signal show when the signal in rear of it is to be a flashing yellow?

Answer 15

Flashing Yellow

Question 16

Once a signal displaying a flashing yellow is approach cleared to a steady aspect, what aspect will the signal show if one of the conditions of the step up is removed?

Answer 16

Red

Question 17

Is a flashing yellow or approach cleared signal required for a near-end conflict if the route speed is restricted to 25km/hr or less?

Answer 17

No

Question 18

Why do offset yellows not lock or prove a conventional overlap?

Answer 18

Offset yellows end in either a buffer stop or another main signal with facing crossover or catch points to protect the main line.

Question 19

When are flashing green signal aspects used?

Answer 19

When a main route enters territory that requires a separate authority to enter in addition to the authority governed by the flashing green main signal.

Question 20

What is the difference between approach locking clear and comprehensive approach locking?

Answer 20

Approach locked once cleared sets up approach locking the moment a signal is cleared, such that even when a train is not on the approach, and a signal call is removed, approach locking must time out.
Comprehensive locking will only trigger the approach locking timer if a train is occupying approach tracks at sighting distance when the signal call is removed.

Question 21

Which type of approach locking should be applied if the approach to a signal is short or non-track circuited?

Answer 21

Approach locked once clear

Question 22

How is approach locking cleared once effective

Answer 22

For both types:
- Until released by elapse of the approach locking time
For comprehensive locking:
- Passage of a train past signal
- Vacation of the approach tracks

Question 23

What is sighting distance for the purposes of approach locking?

Answer 23

400m or 15s at line speed, whichever is greater.

Question 24

What is the minimum approach track required if sighting is limited on the approach to a signal?

Answer 24

200m

Question 25

How is approach locking time calculated?

Answer 25

The approach locking times table in the signalling principles document

Question 26

How do you decide what the approach locking release time for a approach lock once clear would be?

Answer 26

It is calculated assuming the length of the approach tracks would be the same as if it were comprehensive approach locked.

Question 27

What is the minimum overlap allowable?

Answer 27

100m

Question 28

Can overlaps be shared?

Answer 28

Yes, dependent on track layout

Question 29

What is required to be proven in the overlap to clear a signal?

Answer 29

All trailing points in overlap shall be detected and all tracks shall be proved clear.

Question 30

Are facing points in the overlap detected?

Answer 30

Not generally.