DEFINITIONS

• PERMISSIBLE SPEED – The authorized maximum speed over a section of line.

• TEMPORARY SPEED RESTRICTION – A speed, less than the permissible speed, applied for a pre-planned period not normally exceeding 6 months.

• EMERGENCY SPEED RESTRICTION – A speed restriction not shown in the Weekly operating Notice (WON), or which is more restrictive than shown, or which applies at a time other than that shown in the WON.

• WEEKLY OPERATING NOTICE– The official printed notice advising drivers of alterations to permissible speeds.

AUTHORISATION

• The value of all permissible speed and temporary speed restrictions shall be authorized by the Infrastructure Controller.

• On lines which are used in both directions, it is possible to authorize different speeds for each direction of travel.

CLARITY OF SIGNING

Signing of speeds and restrictions should give clear and unambiguous information to  the driver.

All boards and indicators should generally be placed to the left of the track. In cases where it is not possible to do so they should be placed on the right hand side after due verification that they would not cause any confusion to the driver and/or be misread as applying to another line.

Positioning should be considered in relation to all other signs/indicators so that the information conveyed to the driver is clear.

Permissible speed Indicator

* Speed indicators for standard speeds shall comprise a single indicator displaying  the speed.

Differential speeds

Differential (Speed Restriction) : A speed restriction having two varying restrictions, each of which is applicable to different types of train.

Speed indicators for standard differential speeds shall comprise a single indicator displaying  the lower speed above the higher.

Permissible speed Indicator- Converging junction.

* Where permissible speed beyond a junction is the same as that on the higher speed route through the junction and is higher than the speed on the converging route, a speed indicator is not required for trains approaching from the converging route.

* It is permissible to provide a miniature speed indicator as a repeat sign immediately after a converging junction where the permissible speed beyond the junction is higher than that on the converging route.

Permissible speed Indicator- Diverging junction : 

* A speed indicator with an arrow indicating the direction of the diverging route shall be provided immediately before any diverging junction over which there is a reduction in speed.

*  Where a lower permissible speed applies equally to both the routes a single permissible speed indicator shall be provided without directional arrows.

* Where differential speeds commence for each route at a diverging junction, two indicators shall be positioned side by side. Arrows shall be provided to indicate any divergence.

Temporary Speed Restrictions – Procedures

* The infrastructure controller shall devise and apply procedures for the administration, implementation, alteration and withdrawal of temporary speed restrictions. The procedures shall be documented and responsibilities shall be clearly defined.

* Any temporary alterations required are fully documented and approved by the infrastructure controller, and the implementation of the alterations is co-ordinated with the introduction and withdrawal of the temporary speed restriction.

* Equipment is provided and removed at the correct time, is correctly positioned.

*  Implementation of temporary speed restriction shall only commence after notification to the drivers has been given through WON. Where this is not possible ,it shall be treated as a emergency speed restriction.

*  Temporary speed restrictions are generally for less than six months period.

Emergency Speed Restriction

The infrastructure controller shall have a documented procedure for advising emergency speed restrictions to drivers.

PERMANENT SPEED RESTRICTIONS

TPWS will be provided to protect Permanent Speed Restrictions on passenger lines where the approach speed is 60mph or more, and the speed reduction is one third or more.

PSR INITIAL SELECTION

Initial selection for fitment of TPWS on a PSR is done as per flowchart in Appendix C of RT/E/S/10137 Issue 3.

Additionally TSRs that are planned to be in place for greater than six months but not exceeding 12months  shall be considered for fitment subject to risk assessment in accordance with flowcharts in Appendices D & E of RT/E/S/10137 Issue 3.

PSRS REQUIRING FITMENT

PSRS REQUIRING FITMENT:

A  Plain Line on curve

D  Approach to converging junction

Ei  Approach to vehicular level crossing

G  Approach to Terminal Platforms

I  Provided for Reduced Signal Spacing / Overlap

Jii  Provided for Asset protection safety

Ni  Diverging Junction – Signal not Approach Released

Niii  Diverging Junction with splitting distant (No Approach Control Signalling)

PSRS NOT REQUIRING FITMENT – EXCLUSION CODES

B  Diverging Junction – Approach Released from Red

C  Diverging Junction – Approach Released from Y/YY

Eii  Approach to footpath or bridleway crossing

EXI  No protection provided to passenger trains due to freight   train timer issue

F  No longer used (was PSRs on RETB Lines)

H  Approach to Emergency crossovers

Ji  Provided for Asset Protection (Commercial)

K  Provided for Gauging or Aerodynamic Purposes

Mi  Attainable Speed less than 60MPH

Mii  Attainable speed less than agreed Excessive Speed

Nii  Diverging Junction indicated by Flashing Aspects

Q  Trackworker protection

PERMANENT SPEED RESTRICTIONS

Figure below shows the general positioning layout of the OSS on the approach to a speed restriction.

Following the initial selection, final selection shall be carried out in accordance with Appendix E of RT/E/S/10137 Issue 3, using Excel spread sheet TI-14_6.xls

Due to the complexity of determining loop positions and the iterative process of determining fitment criteria based on issues involving train performance, these calculations shall only be made by using the design tool developed and validated specifically for this purpose by AEA Technology Rail – “TPWS at Speed Restrictions: Loop Positioning Spreadsheet – June 2003 Issue 6.0” (TI-014_6.xls). The input page for general application is shown in the next slide.

Railway Direction Indicator:- Direction Indicator is a display along the trackside at critical locations that inform the train operator of the direction of the path ahead.

1. These indicators display a text sign based on the command of the system management center. The text will indicate the next route as being a mainline move or a depot/shunt move. However, they do not indicate that the approaching train has been authorized to proceed along the indicated route.

2. Direction Indicators will be provided at locations in which a non-passenger move and a passenger move may be made and at branches.

3. Direction Indicator is a display provided at facing points where there is a move for which it is necessary, for operational purpose, to indicate the route to be taken to the train operator.

4. The SMC will provide the route information via the PLC non-vital outputs to the DI in order for it to illuminate.

5. The SMC will remove the output indication to the direction indicator when the train has been reported as having passed the direction indicator.

6. It is visible to the train operator when the train is stationary.

7. The aspect displayed shall be Lunar white.

8. Mixed Mode Area: At locations where a Direction Indicator is required, and there is a shunt signal(or) main signal required for Metropolitan line trains, both will be provided. This is to give consistent operational instructions to TBTC train drivers regardless of location.

9. The applicable DI will be blanked if the next destination on an SMC route assignment passes through an SCS region where the SCS is operating in DMC or LCP mode.

10. All the DIs associated with a VCC will be blanked if the communication between the VCC and SMC is severed.

11. When the RS sign is illuminated, then DIs will not be lit, If the RS and DI are located in the same post.

Railway Direction Indicator 

TYPES:

Two series of DI units are required, they are

1. Open section and

2. Tunnel section.

DI Symbol is shown in SSP:

Types of Signals :- Signal is a medium to convey a particular pre-determined meaning in non-verbal form.

Multiple Aspect Color Light Signal (MACLS): Multiple means more than 2 indications .They may have 3 or 4 different aspects or indications to be given to the driver. These signals have longer range of visibility and Improved reliability.

Classification of CLS:

Manual Stop Signal :

Each aspect of the signal is represented by a circle. A horizontal line inside the circle indicates Red aspect, an inclined line the yellow aspect and vertical line the Green aspect. The normal aspect of the signal is shown by double line.

Permissive Signal (Distant Signal):

Shall be located at an adequate distance in rear of the stop signal, the aspect of which it pre- warns. The normal aspect of permissive signal is „Single Yellow„ where 2 distant signals are provided to pre- warn the stop signal, the outer most signal, to be located at an adequate distance from the first stop signal, shall be called the distant signal and the other called the inner distant signal, with the distant capable of displaying „ attention „ or „ proceed‟ aspect only .

To distinguish between stop signal and permissive signal „ P „marker board (letter in black on white board) is fixed to the permissive signal.

Automatic Stop Signal :

The normal aspect of an automatic signal is green and is indicated by the double vertical line, unlike the manual signal where the normal aspect is red and indicated by double horizontal lines. An automatic signal has an „A‟ marker plate fixed to the signal post to distinguish it as an automatic signal. Letter „A‟ in black on white circular disc.

Semi-automatic Stop Signal :

An illuminated „A‟ marker distinguishes a semi – automatic signal from a fully automatic signal. Letter „A‟ against black back ground is illuminated when working as an automatic stop signal and letter „A‟ extinguished when working as a manual stop signal.

Location of Railway Signals

Home Signal: On single line, shall be placed at not less than 300 Mts. in rear of the first facing point. On double line may be located at a distance of not less than 180 Mts. in rear of the facing points or BSLB.

Distant Signal: On single line or double line shall be placed at an adequate distance of normal braking distance which shall not be less than 1 KM from the stop signal. If the second distant is used, the inner distant is to be 1 KM in the rear of home signal (first stop signal) and outer distant is to be 1 KM in rear of inner distant.

Routing Signal: Shall be placed just in the rear of the facing points to protect.

Starter Signal: Placed in the rear of the facing point or fouling mark of the converging lines such that they should protect the adjacent running line.

Advanced Starter: Shall be placed outside all the connections on the line to which it applies, and shall not be less than 120 Mts. from the outer most point on single line. On double line this distance is from the starter signal and in special case upto a distance of full train length beyond outer most point where frequent shunting is involved the main line.

Railway Signals Location | Home Signal | Distant Signal | Routing Signal | Starter Signal | Advanced Starter

Markers & boards

Warning Board: Provided to warn the driver that he is approaching a stop signal. To
draw attention of the driver in the night, self-reflecting sheets are fixed. It is located not
less than 1.5 Kms. in rear of FSS. Where double distant is provided, warning board is
dispensed with.

Shunting Limit Board

Provided on single line sections where shunting in the face of
approaching train is permitted. Placed at a distance not less than 180 Mts. from the
opposing First stop signal.

Block Section Limit Board

Provided on double section where there are no facing points or the outer most points at the approaching end are trailing. It shall be placed at a distance not less than 180 Mts. from the first stop signal.

Outlying Siding

Where an intermediate siding taking „OFF‟ in the facing direction in passenger running line outside station limits is provided with „S‟ marker board to indicate  that a siding is taking „OFF‟ from main line.

Markers & boards | Shunting Limit Board |  Block Section Limit Board | Outlying Siding

All over the world Railway transportation is increasingly used, as this mode of transport is more energy efficient and environmentally friendly than road transportation. Trains move on steel rail tracks and wheels of the railway vehicle are also flanged Steel wheels. Hence least friction occurs at the point of contact between the track & wheels.

Therefore trains carry more loads resulting in higher traffic capacity since trains move on specific tracks called rails, their path is to be fully guided and there is no arrangement of steering. Clear of obstruction as available with road transportation, so there is a need to provide control on the movement of trains in the form of Railway signals which indicate to the drivers to stop or move and also the speed at which they can pass a signal.

Since the load carried by the trains and the speed which the trains can attain are high, they need more braking distance before coming to the stop from full speed. Without signal to be available on the route to constantly guide the driver accidents will take place due to collisions.

There are basically two purposes achieved by railway signalling.

1. To safety receive and despatch trains at a station.
2. To control the movements of trains from one station to another after ensuring that the track on which this train will move to reach the next station is free from movement of another train either in the same or opposite direction. This Control is called block working. Preventing the movement from opposite direction is necessary in single line track as movements in both directions will be on the same track.

Apart from meeting the basic requirement of necessary safety in train operation, modern railway signalling plays an important role in determining the capacity of a section .The capacity decides the number of trains that can run on a single day. By proper signalling the capacity can be increased to a considerable extent without resorting to costlier alternatives.

The essential components of railway signalling:

The fixed signals provided by the side of the railway track with indication in the form of colour lights are the actual authority to a driver to get in to the portion of the track beyond the signal. At stations the trains may be received on any one of the platform lines. To take the train to any specific track, points are provided.

The purpose of the point on the track is to divert the train from one track to adjacent one. Hence the signal has to be connected to the points in an arrangement called interlocking. This Interlocking arrangement only ensures that a point is correctly set for the particular route or a track and the signal conveys this information to the driver.