The majority of running rails are used to form track circuits to provide a means of proving the absence of trains. The General arrangement is that a low power signal is transmitted from ans end of the track circuits, along one rail, to a receiving device. The other rail forms the return path. When the track is clear, the receiver is energised. When a train is between the transmitter and receiver, its axles provide a low impedance circuit between the two running rails, shunting the signal and causing the receiver to de-energise. The state is the occupied condition.

Bonding plans, in accordance with NR/L2/SIG 11201, shall be provided for all  track circuited areas.

The procedures for inter-disciplinary checking are given in section 5 of NR/SP/SIG/11752.

Symbols for Bonding Plans

Symbols depicting track circuits on bonding plans are to be in accordance with NR/L2/SIG 11201-Mod A17

Non-electrified Areas

In non-electrified areas, the Bonding Plan is generally the responsibility of the signalling contractor, who designs the bonding of all rails. Normal procedures for design details shall be followed. However, the position of IRJs shall be agreed with the permanent way organisation in complex areas by marking up the permanent way scale plan.

Electrified Areas
(except Electrified Area of the Former Southern Region)

In electrified areas, the following procedures, or equivalent, shall be followed, involving both the signalling and electrification organisations. In addition, the positioning of insulated rail joints (and the provision of conductor rail protection boarding, where applicable) shall be agreed with the permanent way organisation, as in section 5.1 of NR/SP/SIG/11752

The signalling organisation shall obtain the base plan for a new electrification scheme at an early stage from the electrification organisation, preferably drawn on a CAD system. To the base plan for new schemes, or to the existing Bonding Plan, the following new or altered requirements shall be added:

1. the position of insulated rail joints,

2. identification of the insulated rail and traction (or common) rail, in single rail track circuit areas,

3. all track circuit bonding, identifying any yellow bonds necessary track circuit feed and relay connections and other details traction bonding essential for track circuit operation all other yellow bonding, including traction cross bonding,

4. all impedance bonds, correctly spaced, in double rail track circuit areas,

5. conductor rail gapping requirements, where applicable signals requiring structure bonding (a.c. and dual electrified areas).

6. When checked, a certification block shall be added and a minimum of two prints issued to the electrification organisation. One of these shall be returned to the signalling organisation amended in blue to show the full traction bonding for approval. This copy shall be signed by both the signalling and electrification organisations.

7. The source record shall be amended and two additional copies issued to the electrification organisation for installation. If modification is required during installation, one copy shall be modified in blue and returned to the signalling organisation for the source record to be updated.

Electrified Area of the Former Southern Region

Normal procedures for design details shall be followed for Track Plan production and agreement shall be obtained with the permanent way organisation as described in section 5.1 of NR/SP/SIG/11752 Here, the signalling organisation produces a separate Track Plan derived from the permanent way Track Layout Drawing. This is issued to the electrification organisation at the earliest practicable opportunity, which produces separate traction return Negative Bonding Plans and Conductor Rail Plans. The signalling organisation shall provide the following details on the Track Plan:

1. the position of insulated rail joints,

2. identification of the insulated rail and traction (or common) rail by liaison with electrification organisation, in single rail track circuit ares areas.

3. all track circuit bonding, identifying any yellow bonds (if applicable) track circuit feed and relay connections and other details,

4. all impedance bonds, correctly spaced, in double rail track circuit areas and the position of AWS inductors,

5. signals requiring structure bonding (a.c. and dual electrified areas only).

6. The electrification organisation provides the following details on the conductor rail plan:

7. Position of conductor rail by liaison with the signalling organisation, in single rail track circuit areas, traction isolation hook switches, conductor rail gaps and the position of AWS inductors (derived from the Track Plan).

8. The signalling organisation shall check that the signal rail is designed on the side remote from the conductor rail, that the conductor rail is adequately gapped so as not to foul signalling equipment and that there are no positive traction cables in the vicinity of AWS inductors. The electrification organisation provides the following details on the Negative Bonding Plan:

9. position of insulated rail joints (derived from the Track Plan),

10. identification of the insulated rail and traction (or common) rail (derived from the Track Plan),

11. all traction bonding,

12. all impedance bonds (derived from the Track Plan), together with traction leads,

13. conductor rail protection boarding,

14. the position of AWS inductors (derived from the Track Plan).

The signalling organisation shall check that the Negative Bonding Plan agrees with the Track Plan. The traction bonding essential for track circuit operation shall be checked, identifying all yellow bonds and marking any additional yellow bonding (if applicable), checking that protection boarding has been provided where necessary and that there are no negative traction cables in the vicinity of AWS inductors.

15. A certification block shall be applied to these drawings for signing.

16. Any deficiencies shall be marked on the Negative Bonding Plan before returning it for certification, as in section 5.2 of NR/SP/SIG/11752. The electrification organisation then issues the Negative Bonding Plan for installation.

Railway Bonding Details in D.C. Electrified Areas:- Separate Track Plans and Negative Bonding Plans are only used in the former Southern Region.

The impedance bond rail connections and the bond to bond connections must be shown on bonding plans. Traction return cross bonding between lines is the responsibility of the electrification organization and need not be shown on track plans for the former Southern Region, but are required on bonding plans for d.c. traction systems elsewhere.

Traction return bonding essential to the operation of track circuits must be shown on all bonding plans (see Figure H3).

Railway Bonding Details in D.C. Electrified Areas

Minimum length of track section (Railway Bonding Details in DC Electrified Areas)

The minimum length of a track section shall be greater than the harmonized maximum spacing between adjacent axles of vehicles, as set out in section 3.1.2.1 of ERA/ERTMS/033281 unless alternative safeguards are provided to prevent the track section from showing clear when a vehicle is standing over it.

ERA/ERTMS/033281 sets out the harmonized maximum spacing between adjacent axles of vehicles of 20 m.

Where the work involves track replacement only, the minimum length of a track section of 18.3 m could be retained for work that does not include a change to the train detection system’s capability.

Where the minimum length cannot be achieved, alternative safeguards (for example, sequential proving of the adjacent track section) are provided to prevent the track section from being falsely detected as clear.

Examples of a minimum length of track section are shown in Fig below

Dimensions Value

D = Distance between inner joints of staggered pairs   Not less than 11 m if both pairs staggered < 1.6 m. Otherwise, not less than 20 m  

E = The shortest distance between a staggering pair of IRJs and the boundary of a track section ………..  20 m minimum  

L = Effective length of track circuit   20 m minimum  

S = Physical stagger…. 2.1 m max: Signal rail overlap on electrified lines and 2.6 m max: Other cases  

Railway Insulated Rail Joints:- Insulated Rail Joints (IRJs) are required to join together mechanically but no electrically. they are required for the following purposes:

1. to define the limits of jointed track circuits,
2. to provide insulation between rails at S&C, necessitating track circuit transpositions,
3. where transpositions are required for other purposes,
4. to provide traction return isolation.

The following shall be considered relative to IRJ Provision in S&C as constrained by permanent way engineering considerations:

1. IRJs adjacent to cast crossings shall be avoided wherever practicable.
2. IRJs, run over in the high-speed route shall be avoided as far as practicable.
3. There shall be a minimum distance of 200m between the chair of rail fastenings of opposite polarity/phase to reduce the probability of failures due to metallic litter, etc.

Railway Insulated Rail Joints

Insulated Rail Joints – Buffer Stops

Buffer Stop 

Rail-mounted buffer stops in track circuits areas must be fully isolated, by one of the following means:

1. Provision of an insulated design of buffer stop.
2. Provision of ITJs in both rails, for a double rail track circuit, or
3. Provision of an IRJ in the insulated rail, for a single rail track circuit.

in order to ensure detection of the shortest vehicle, the IRJs shall be located at 4m + 0.5m from the face of the buffer stop. the position of the IRJs for friction buffer stops shall be determined from figure F8. The type of IRJ must be of a design that offers similar tensile strength to conventional steel fish plates.

Insulated rail joint specification

Glued joint in railway track in Hindi

Rail joints in railway

Insulated Block joint railway

Insulated rail joint wiki

Insulated Block joint maintenance

Glued joint definition

Insulated rail joints are obtained by placing which

Railway Use of Axle Counters Fouling Point Clearance point:- The Design requirements for train detection systems includes the following:

1. Interface with authorized rail vehicles (positioning of IRJs, minimum track circuit lengths, which may be dependent on permissible speed, and interlocking measures to mitigate against any deficiencies)
2. Interface with the permanent way (IRJs, standard rail bonding with pre-drilling requirements, and S&C bonding configuration)
3. Interface with electric traction infrastructure (single or double rail configuration and impedance bond position)
4. Interface with the interlocking system (operating times and measures to mitigate against the false release of interlocking when there is a significant risk)
5. The requirement for secure power supplies and/or battery back up

Design Consideration for choice of train detection

1. The need to detect vehicles on poor rail surfaces.
2. The need or otherwise to avoid insulated rail joints.
3. The need for immunity to AC and/or DC traction interference.
4. The need to achieve maximum reliability at an economic cost.
5. The need to track circuits through complex S&C.
6. The type of sleepers, where ballast resistance is critical.
7. The length of a train may need to be measured.

Different types of train detection systems Axle Counters Fouling Point Clearance point

1. Track circuits
2. Axle counters
3. Other types of wheel detector, e.g, treadle, electromagnetic proximity device(used for HABD)
4. Supplementary systems, e.g, track circuit assistor interference detector(TCAID), track circuit interrupter.

Key Attributes & Limitation of Track circuits

Use of Axle Counters – Axle Counters Fouling Point Clearance point

Fouling Point

1. This is a position a short distance away from the point of running line divergence (crossing nose). Should any part of a vehicle on one track be between the crossing nose and the fouling point, it will make physical contact with any vehicles passing on the other route.

2. The fouling point occurs where the distance between the running edges of the two rails is 1970mm, measured at right angles from the diverging line.

3. In the case where tracks become parallel with a running edge separation of less than 1970mm, the fouling point occurs where the tracks first become parallel.

Clearance point

Determination of clearance point:- Figure shows the relationship between the clearance point and the fouling point. In particular, it depicts that the clearance point is determined by adding the maximum vehicle end overhang* allowed for a line and the allowance of 1600 mm. The allowance includes the rollback allowance of 1300 mm, which is provided to accommodate potential rollback after the train has come to a stand.

maximum vehicle end overhang :

1. a) 5000 mm for new high-speed lines.
2. b) 4200 mm for other lines.

Determination of clearance point