Train Protection & Warning System (TPWS) Basic Concept:- Presentation

TPWS is a system designed to stop train:

* Passing A Signal At Danger Without Authority.
* Approaching A Signal At Danger Too Fast.
* Approaching Speed Restriction Too Fast.
* Approaching Buffer Stop Too Fast.

TPWS consists of two sensors:

* Train Stop Sensor (TSS)
* Over Speed Sensor (OSS)

Both the OSS and TSS have two loops

* Arming loop
* Trigger loop.

TPWS will only be energised if the signal is at red.

 

 

 

TSS / OSS

* A Train Stop Sensor (TSS), which immediately applies the brakes of a train passing :

A SIGNAL AT DANGER

* An Over Speed Sensor (OSS), which immediately applies the brakes of a train going too fast towards :

A SIGNAL AT DANGER; A SPEED RESTRICTION; A BUFFER STOP

TPWS : Equipment

 

 

TPWS : TSS (Train Stop Sensor)

 

 

* TSS positioned at the signal post (Foot of the signal).

* Trigger Loop placed immediately after Arming Loop.

* Brakes applied on any train passing over TSS when signal at danger.

 

TSS – can stop a train at 40MPH within overlap

 

 

 

TPWS : OSS(OverSpeed Sensor)

 

 

TPWS : OSS Over Speed Sensor

OSS loop positions based upon line speed and gradient

Timer:

• Passenger Train – 974 ms
• Freight Train –  1218 ms

 

If the TPWS loop is energized it emits a radio signal. When a train passes over the Arming loop this starts a timer on the train.

If the train passes over the Trigger loop with the timer still running then an emergency brake application is made. 

 

OSS- can stop a train at 75MPH within overlap.

 

• TPWS LOOP

 

AWS & TPWS

TPWS is designed as an add-on to AWS

TPWS – Not giving any indication to the driver

TPWS – NOT Required for all main colour light signal

 

EXEMPTION CODES:

L- Not Protecting Passenger Line

S- Shunting Only / Not Displaying Stop Aspect

TS- Alternative Train Protection System

F- Track Layout Provides Protection

SS- Out Of Use Signal

 

SOD – Safe Overrun Distance

 

 

RELEVANT STANDARDS

Railway Group Standard

         GE/RT8030  – Requirements for a Train Protection and Warning System (TPWS)

Network Rail Company Standards

         RT/E/S/10133 – TPWS Signalling Interface Design Requirements

         RT/E/S/10137 -TPWS Selection of signals

         RT/E/S/10138 -TPWS Transmitter Loop requirements and positioning