Railway signalling systems connect interlocking rooms, relay rooms, lineside cabinets and exposed trackside equipment through long power, control and communication cables. These conductive routes can carry lightning-induced surges, switching transients and earth-potential differences toward sensitive signalling interfaces. [9] [10]
Effective railway signal surge protection is not achieved by selecting the SPD with the highest kA rating. The device must limit transient voltage without changing the normal signal, creating an unacceptable path to earth or introducing a failure mode that conflicts with the railway safety system. [7] [10]
Select a railway signalling SPD by the exact protected interface, not by nominal voltage or surge-current rating alone. Confirm the circuit function, maximum continuous voltage, operating current, waveform or data rate, permitted voltage drop, earthing arrangement, acceptable leakage, protection modes and failure behaviour before choosing a model. [4] [9] [10]
- Review power, signal, control and communication cables separately.
- Place protection at defined cable-entry and equipment boundaries.
- Check both normal operation and foreseeable SPD failure conditions.
- Do not connect a floating or insulation-monitored circuit to earth without approved system review.
- Confirm operator, system-vendor and project approval requirements before ordering.
Índice
Why Railway Signalling Requires Interface-Specific Surge Protection
A railway signalling installation may contain ordinary building power, dedicated signalling power, relay circuits, track circuits, point-machine circuits, axle-counter interfaces, serial data and Ethernet.
These circuits do not share the same voltage, current, frequency, impedance or safety function. A device suitable for a general 230 V AC cabinet input may be unsuitable for a floating signalling supply or a low-energy detection circuit. [9] [10]
IEC 62236-4 specifies electromagnetic emission and immunity requirements for railway signalling and telecommunications apparatus. IEC 62425 addresses the functional-safety lifecycle of safety-related electronic signalling systems. [6] [7]
These standards help define the railway environment and system-safety process. They do not make an unreviewed industrial SPD automatically suitable for a railway signalling interface.
Normal operation
The SPD must not introduce excessive voltage drop, capacitance, insertion loss, leakage or impedance imbalance.
Failure condition
The project must consider whether an aged or failed SPD could short conductors or connect a monitored circuit to earth.
Trackside environment
Temperature, humidity, vibration, pollution and enclosure conditions must match the actual installation location.
Project approval
Product-standard compliance does not replace operator approval, system-vendor acceptance or project validation.
Where Can Surges Enter a Railway Signal System?
Railway signalling equipment is distributed over long distances. Conductive cables can leave a protected building, follow an exposed trackside route and terminate at field equipment with a different local earth potential. [9]
A transient can therefore enter through several routes and from either end of a cable. Every metallic conductor entering or leaving an equipment location should be included in the project surge-risk review.
| Surge entry path | Fuente típica. | What must be reviewed |
|---|---|---|
| Incoming AC power | Lightning coupling, utility switching or an upstream electrical fault | Supply type, earthing arrangement, TOV exposure, short-circuit conditions and equipment withstand |
| Long trackside cable | Inductive or capacitive coupling from nearby lightning | Cable length, route, shield, protected equipment at both ends and local bonding |
| Rail-connected or detection circuit | Rail potential, traction-related disturbance or nearby faults | Standing voltage, signal waveform, insulation, earth reference and approved protection mode |
| Communication copper | External data cable, remote cabinet or mast connection | Data rate, bandwidth, insertion loss, capacitance, shield connection and line power |
| Control and indication line | Long conductors connected to signals, point machines, crossings and detectors | Continuous current, inrush, series resistance, voltage drop and failure state |
| Earth-potential difference | Lightning current or a high-voltage fault to earth | Local EPR conditions, remote earth paths and the approved equipotential bonding design |
Procurement conclusion: an AC power SPD does not protect external signal, control and communication interfaces. Each conductive path requires a separate compatibility review.
How Should Protection Be Layered Across the Railway System?
Railway signal surge protection should follow the physical cable route and the boundaries between the central equipment room, intermediate cabinet and field equipment.
The first protection stage reduces surge energy at the location boundary. Additional protection may be required closer to sensitive equipment when cable length, equipment immunity or the remaining voltage requires another coordinated stage. [4] [9]
Central equipment room or interlocking location
Review incoming facility power, dedicated signalling power, external communication services and every copper signalling circuit leaving the room.
Boundary protection should be installed close to the relevant cable entry. Long conductors between the entry point, SPD and protected equipment can increase the effective voltage during a fast transient. [4]
Relay room or intermediate cabinet
An intermediate cabinet can receive a transient from either side of a long external cable. Protection should be placed at the defined cable-entry boundary rather than deep inside the cabinet after a long unprotected conductor run.
For a two-port SPD, confirm line and equipment orientation, load-current capacity, series resistance, terminal arrangement and the effect of removing the protection module.
Lineside cabinet and trackside equipment
Signals, point machines, axle counters, track circuits and level-crossing equipment can be connected through long, exposed cable routes.
Protection at the equipment-room end may not sufficiently limit a transient appearing near the remote end. Both cable boundaries may require review, but the final arrangement depends on circuit insulation, earthing, equipment design and operator requirements. [4] [9]
Adding line-to-earth protection to a floating or insulation-monitored circuit may create a new leakage or failure path. The permitted protection modes and earth connection must be confirmed from the approved system design.
Power Circuit Protection Starts by Identifying the Supply
The first decision is whether the circuit is ordinary facility power or dedicated railway signalling power. Their voltage, earthing, fault-current and approval requirements can be different.
General low-voltage AC supply
IEC 61643-01:2024 contains common requirements for SPDs, while IEC 61643-11:2025 applies to SPDs connected to AC low-voltage power systems. [1] [2]
Selection still depends on the actual supply voltage, earthing arrangement, temporary overvoltage exposure, prospective short-circuit current, external backup protection and required voltage protection level.
A Type 1, Type 2 or coordinated AC SPD arrangement may be relevant to the building supply or a general cabinet input. It should not automatically be extended to a signalling safety circuit.
Dedicated signalling AC supply
Railway signalling power may use an isolated or IT arrangement. Earth-leakage monitoring may be used to detect the first connection between a live conductor and earth. [9] [10]
In this situation, the supplier needs the maximum voltage between conductors and from each conductor to earth. The SPD’s normal leakage and foreseeable failure behaviour must also be reviewed.
Dedicated signalling DC supply
For a DC signalling power circuit, confirm maximum continuous voltage, fault voltage, continuous current, inrush current, available fault current and the characteristics of the power source.
IEC 61643-41:2025 applies to SPDs connected to DC power circuits up to 1,500 V DC and is used together with IEC 61643-01. The standard notes that careful consideration is required when the source does not have the linear voltage-current characteristic assumed by its tests. It can be relevant to railway applications where no more specific product standard exists, but its applicability must be confirmed for the particular circuit. [1] [5]
IEC 61643-41 applies to DC power circuits. It should not be treated as the general product standard for a coded signalling, detection or communication interface.
When the selected protection technology can conduct follow current, the available DC fault current and the required disconnection method must be reviewed before approval. [1] [5]
An unnecessarily high operating voltage can leave a higher residual voltage at the protected equipment. An operating voltage that is too low can expose the SPD to continuous or temporary overvoltage stress.
Signal, Track and Control Circuits Must Be Reviewed Separately
“Railway signal line” is not one electrical interface. Track circuits, signal-lighting outputs, relay loops, point-machine drives and axle-counter interfaces can operate with different voltages, currents, frequencies and waveforms. [9] [10]
| Circuit type | Important characteristics | SPD compatibility risks |
|---|---|---|
| Track circuit | DC, low-frequency AC, audio-frequency or coded operation | Clamping voltage, capacitance, attenuation and rail-related standing voltage |
| Signal lighting | AC or DC output, electronic driver, long field cable and possible inrush | Load current, residual voltage, common-mode stress and equipment-end bonding |
| Point-machine drive | Motor or actuator current, polarity or phase reversal and long conductors | Current capacity, voltage drop, reversal compatibility and follow current |
| Point detection | Safety-related feedback, relay or coded detection | Earth leakage, short-circuit failure and altered detection thresholds |
| Axle-counter interface | Manufacturer-specific sensor, power and data interface | Bandwidth, impedance, pin arrangement and system-vendor approval |
| Relay input or output | Coil current, contact state, loop resistance and external field wiring | Series resistance, voltage drop and safe revealed failure |
Buyer meaning: one “24 V railway SPD” should not be approved for every 24 V interface. Nominal voltage does not describe the signal, load, earthing or safety function.
Communication Line Protection Must Preserve Data Performance
Railway monitoring and control systems may use serial interfaces, Ethernet, copper telecommunications lines, remote I/O or manufacturer-specific transmission systems.
IEC 61643-21:2025 applies to SPDs connected to telecommunications and signalling networks, including networks that carry power and data on the same conductors. IEC 61643-22:2015 provides selection, operation, location and coordination principles for these devices. [3] [4]
Product-standard compliance is useful evidence. It does not prove compatibility with every railway protocol, connector, cable arrangement or safety-related communication system.
Confirm these communication parameters
- Physical interface, connector and terminal arrangement.
- Number of conductors and cable-shield connection.
- Nominal and maximum line voltage.
- Data rate and required bandwidth.
- Permitted insertion loss and impedance imbalance.
- Maximum capacitance and series resistance.
- Power carried on the line, including PoE or another line-powered function.
- Common-mode and differential-mode protection requirements.
- Permitted connection to chassis, bonding network or earth.
Fibre-optic transmission removes a conductive data path, but the associated power supply, converter, cabinet, screen or metallic strength member may still require surge and bonding review.
Which SPD Parameters Must Match the Railway Interface?
The most important column is “Why it matters.” It shows why a datasheet value can change protection performance, normal operation or project approval.
| SPD parameter | Qué confirmar | Por qué es importante |
|---|---|---|
| Uc o tensión máxima de operación continua | Maximum line-to-line and line-to-earth standing voltage | Prevents continuous stress and unwanted conduction |
| Up or measured limiting voltage | Equipment impulse withstand and required coordination margin | A high current rating is not useful if the remaining voltage is too high |
| Surge test category and waveform | Required test method, current level, voltage level and protection mode | Ratings produced with different waveforms cannot be compared by kA alone |
| Continuous and peak load current | Normal current, inrush, reversing current and short-duration operating current | Avoids overheating, excessive voltage drop and interruption of the circuit |
| Resistencia en serie | Maximum permitted loop resistance and conductor loss | Important for long cables, relay loops and low-voltage loads |
| Bandwidth and insertion loss | Actual signal frequency, coded waveform or data rate | Prevents distortion or loss of detection and communication signals |
| Capacitance and impedance balance | Interface limits and cable characteristics | Can affect detection thresholds and high-frequency transmission |
| Leakage and insulation resistance | Permitted current to earth and insulation-monitoring thresholds | Avoids an unintended or hidden path to earth |
| Modos de protección | Line-to-line, line-to-earth or a coordinated combination | The wrong earth reference can change circuit behaviour |
| Failure behaviour | Open circuit, short circuit, earth fault, disconnection and status indication | The failed SPD must not create an unacceptable system state |
| Clasificación ambiental | Temperature, humidity, vibration, pollution, enclosure and mounting position | Trackside and equipment-room conditions can differ substantially |
| Mechanical interface | Terminal size, mounting, footprint, replaceable module and marking | An electrical parameter match does not guarantee installation compatibility |
Procurement conclusion: request the full datasheet, protection circuit, transmission data, failure information, installation instructions and exact test-report scope before approving a railway SPD.
Why SPD Failure Mode Matters in Railway Signalling
Many railway signalling circuits depend on maintaining electrical isolation between conductors, between separate circuits and between a circuit and earth.
An SPD adds components between these points. If a protection component fails with low resistance, it may create a connection that did not exist in the original circuit. [7] [10]
What is an unrevealed earth fault?
An unrevealed earth fault is a connection to earth that exists without producing an immediate visible or detected failure.
A second fault on another conductor can then create an unintended current path through earth. In a safety-related signalling system, this possibility must be included in the system safety assessment rather than assumed to be harmless. [7] [9] [10]
The technical review should determine:
- Whether an internal protection component can fail with low resistance.
- Whether that failure is line-to-line or line-to-earth.
- Whether the failure will be revealed by an alarm, fuse, disconnector or leakage monitor.
- Whether the circuit moves to the project-defined safe state.
- Whether removing the protection module changes or interrupts the signal circuit.
- Whether end-of-life indication is independent from the normal signal state.
Earthing and Equipotential Bonding Determine Real Protection Performance
An SPD does not make surge current disappear. It diverts the current through a defined path. The SPD, protected equipment, cabinet, cable screen and bonding system must therefore be arranged so that damaging voltage differences are limited during the transient. [4] [9]
Keep surge-current paths short and direct
Fast surge current produces voltage across conductor inductance. Long SPD connections can increase the voltage appearing at the protected equipment even when the SPD datasheet shows a low protection level. [4]
Install the SPD close to the relevant cable entry or protected interface. Avoid unnecessary loops and keep unprotected conductors separated from protected internal wiring.
Use the approved railway bonding concept
The nearest general earth bar is not automatically the correct connection point.
Railway installations may have constraints related to traction return current, high-voltage earth faults, earth-potential rise, stray current, separate earth systems and signalling insulation monitoring. [9] [10]
Transport for NSW TS 05258:2.0, for example, includes operator-specific requirements concerning earth-potential-rise withstand, residual current to earth, signalling IT supplies and SPD failure modes. Those requirements belong to that operator and must not be copied blindly into another railway project. [10]
During a fast transient, the local voltage difference can be dominated by conductor and bonding impedance. Physical layout and equipotential bonding remain critical.
Which Standards Apply, and What Do They Prove?
Railway surge protection may involve SPD product standards, railway EMC standards, environmental standards, functional-safety standards and operator-specific specifications.
These documents perform different jobs. One certificate must not be presented as proof of every project requirement. The applicable edition and adopted national version must be confirmed for each project.
| Standard or requirement | What it supports | What it does not prove alone |
|---|---|---|
| IEC 61643-01:2024 | Common requirements, tests and ratings for low-voltage SPDs | Compatibility with a specific railway signalling interface |
| IEC 61643-11:2025 | Requirements and tests for SPDs connected to AC low-voltage power systems | Suitability for a safety-related railway signal circuit |
| IEC 61643-21:2025 | Requirements and tests for telecommunications and signalling network SPDs | Compatibility with a specific railway protocol or signalling platform |
| IEC 61643-22:2015 | Selection, operation, location and coordination principles for signalling-network SPDs | Operator approval or system-vendor acceptance |
| IEC 61643-41:2025 | Requirements and tests for SPDs connected to relevant DC power circuits | Suitability for a coded signal, detector or communication circuit |
| IEC 62236-4:2018 | EMC emission and immunity requirements for railway signalling and telecommunications apparatus | SPD surge capability or interface-safe failure behaviour |
| IEC 62425:2025 | Functional-safety lifecycle for safety-related electronic signalling systems | Electrical performance of a particular SPD model |
| IEC 62498-3:2010 | Environmental conditions for signalling and telecommunications equipment | Suitability for the exact cabinet, enclosure or location |
| AS 7708:2017 | Australian railway signalling earthing and surge protection requirements across the asset lifecycle | Acceptance by a railway authority outside its applicable scope |
| Operator or project specification | Approved configurations, additional tests, installation and maintenance requirements | Approval for another railway authority or signalling platform |
| System-vendor acceptance | Compatibility with a defined signalling interface and equipment version | Universal compatibility with all products and wiring arrangements |
Buyer meaning: verify the exact model number, circuit configuration, report edition and approval scope. A certificate for one product family may not cover every voltage, terminal arrangement or railway application.
Why AS 7708 matters
AS 7708:2017 is specifically titled Signalling Earthing and Surge Protection and remains listed as current by the Australian Rail Industry Standards Organisation. Its scope covers design, construction, testing, commissioning, monitoring, maintenance, modification and decommissioning of railway signalling earthing and surge protection. [9]
This makes AS 7708 more directly relevant to railway signalling earthing and surge protection than a general SPD product standard. However, it remains an Australian railway standard and does not replace the requirements of another country, operator or signalling system.
A current operator-specific example
Transport for NSW TS 05258:2.0 was issued and became effective on 23 June 2025. It identifies AS/RISSB 7708, IEC 61643-11 and IEC 61643-21 among the applicable standards for surge protection equipment. [10]
The specification distinguishes general 230 V AC power SPDs, communication-interface SPDs and SPDs used on signalling power or equipment input and output ports. It also states that any SPD used as part of the signalling safety system requires type approval under the applicable TfNSW process. [10]
This is useful evidence of how detailed a railway operator’s requirements can be. It is not a universal specification for every country or railway system.
Common Railway SPD Selection Mistakes
| Incorrect assumption | Why it is risky | Better confirmation |
|---|---|---|
| The highest kA rating is the best SPD. | Residual voltage, leakage and signal performance may still be unsuitable. | Compare Uc, Up, waveform, protection modes and interface limits. |
| All circuits with the same nominal voltage use the same SPD. | Current, frequency, impedance, earthing and safety function may differ. | Identify the exact circuit function and operating waveform. |
| Connecting every conductor to earth gives stronger protection. | It may create leakage or an unsafe failure path on a floating circuit. | Use only the approved line-to-line and line-to-earth protection modes. |
| Protection at the control room protects the remote field device. | A long external cable can receive a transient close to the field end. | Review both cable boundaries and the local bonding arrangement. |
| An IEC certificate equals railway approval. | System compatibility, functional safety and operator requirements remain unverified. | Check type approval, project documents and system-vendor acceptance. |
| A mechanically similar SPD is a direct replacement. | Internal circuits, failure modes, protection levels and reports may differ. | Complete a parameter comparison, sample validation and formal change review. |
Railway Signal SPD Project Review Workflow
A railway SPD enquiry should begin with the protected interface and approval requirements, not with a catalogue model number.
-
Identify the protected function.
State whether the circuit is general power, signalling power, track circuit, signal lighting, point control, point detection, axle counter, relay I/O, serial communication or Ethernet. -
Define the safety and approval boundary.
Confirm whether the circuit performs or supports a safety-related function. Identify the railway operator, signalling manufacturer, system integrator and authorised reviewer. -
Collect complete electrical data.
Provide nominal and maximum voltage, AC or DC, frequency or waveform, continuous current, inrush current, available fault current and acceptable voltage drop. -
Collect transmission data.
For signal and communication interfaces, provide bandwidth, data rate, impedance, capacitance limits and permitted insertion loss. -
Review earthing and failure behaviour.
Confirm floating circuits, earth-leakage monitoring, approved protection modes and the required circuit state following SPD failure. -
Review the physical installation.
Provide cable length, cable route, shield arrangement, cabinet environment, terminal requirements, mounting method and bonding drawing. -
Verify standards and document scope.
Compare product reports, railway specifications, model scope, environmental evidence, installation instructions and maintenance requirements. -
Complete sample and system validation.
Carry out the laboratory, factory acceptance, interface or controlled site testing required by the project before final model approval.
What Must Be Confirmed Before Ordering?
Railway Signal SPD Enquiry Checklist
- Country and railway authority
- Project and signalling platform
- Protected equipment
- Exact interface function
- Safety-related classification
- Voltaje nominal
- Voltaje máximo continuo
- Maximum line-to-earth voltage
- AC, DC and frequency
- Signal waveform or data rate
- Continuous load current
- Inrush or short-duration current
- Available fault current
- Permitted voltage drop
- Permitted capacitance
- Permitted insertion loss
- Floating or earthed circuit
- Earth-leakage monitoring
- Required protection modes
- Required surge tests
- Longitud y ruta del cable
- Shield and bonding arrangement
- Indoor or trackside environment
- Temperature and vibration limits
- Applicable standards
- Type-approval requirements
- Required reports and certificates
- Terminal and mounting requirements
- Status or remote alarm requirement
- Quantity and spare modules
- OEM marking and documentation
Share the Interface Data Before Requesting a Railway SPD Model
LEEYEE can support a preliminary parameter review based on the interface information and project documents you provide. The review can help identify whether an available surge protection product family may be relevant, whether additional adaptation or testing is required, or whether the application is outside the current product scope.
This preliminary review is not railway approval. Final suitability and acceptance must remain with the railway operator, signalling system manufacturer, system integrator and authorised project reviewer.
LEEYEE is a specialized surge protection and low-voltage protection supplier. CNSPD is LEEYEE’s surge protection-focused platform for global technical buyers. Built to Protect. Trusted to Last.
Preguntas frecuentes
Can a standard industrial signal SPD be used for railway signalling?
Not without interface and project review. A device may comply with a general SPD standard but still be incompatible with the railway circuit’s voltage, waveform, leakage limit, failure state, environment or approval requirements.
Is railway signal surge protection selected mainly by kA rating?
No. Surge-current capability is only one parameter. Uc, Up, protection mode, load current, series resistance, capacitance, insertion loss, earth leakage and failure behaviour may be more important for a particular interface.
Does every long trackside cable require an SPD at both ends?
Long external cables often require both boundaries to be reviewed because a transient can enter near either location. The final arrangement depends on circuit insulation, earthing, protected equipment and railway operator requirements.
Can an SPD affect a track circuit or axle-counter interface?
Yes. Series resistance, capacitance, insertion loss, leakage and clamping behaviour can affect detection or communication. Compatibility must be checked at the real operating frequency, voltage and current.
Which standard applies to a railway communication-line SPD?
IEC 61643-21:2025 is a relevant product standard for SPDs connected to telecommunications and signalling networks. The project may also require IEC 61643-22, railway EMC standards, operator specifications, type approval and system-vendor acceptance.
Can IEC 61643-41 be used for every railway DC circuit?
No. IEC 61643-41:2025 applies to relevant DC power circuits. It does not automatically apply to coded signalling, detection or communication interfaces. The actual circuit function and any railway-specific product requirements must be confirmed.
Is IEC 61643-21 compliance enough for railway approval?
No. It provides product-standard evidence. It does not by itself confirm compatibility with a particular signalling circuit, safety function, operator requirement or installation configuration.
Why is earth leakage important in railway signalling?
Some signalling circuits are floating or insulation monitored. An SPD connected to earth can add leakage during normal operation or after failure. The permitted value and monitoring method must be confirmed for the project.
Can a railway-approved SPD be replaced by a similar model?
Not automatically. The alternative may differ in electrical circuit, failure behaviour, terminals, dimensions, protection level and test-report scope. Formal comparison, sample validation and approval may be required.
What information is most important when requesting a railway SPD quotation?
Send the exact interface, maximum operating voltage, current, waveform or data rate, earthing arrangement, permitted leakage, cable route, required tests and approving railway authority.
Can one SPD be described as suitable for all railway systems?
No responsible supplier should make that claim. Suitability normally applies to a defined model, protected interface, signalling platform, installation configuration and approval scope.
Related Technical Reading
These pages explain general surge protection principles. Railway-specific operator requirements, interface compatibility and safety approval must still be confirmed separately.
Referencias
- International Electrotechnical Commission, IEC 61643-01:2024, Low-Voltage Surge Protective Devices – Part 01: General Requirements and Test Methods. Página de publicación oficial de la IEC.
- International Electrotechnical Commission, IEC 61643-11:2025, Low-Voltage Surge Protective Devices – Part 11: Surge Protective Devices Connected to AC Low-Voltage Power Systems – Requirements and Test Methods. Página de publicación oficial de la IEC.
- International Electrotechnical Commission, IEC 61643-21:2025, Low-Voltage Surge Protective Devices – Part 21: Surge Protective Devices Connected to Telecommunications and Signalling Networks – Requirements and Test Methods. Página de publicación oficial de la IEC.
- International Electrotechnical Commission, IEC 61643-22:2015, Low-Voltage Surge Protective Devices – Part 22: Surge Protective Devices Connected to Telecommunications and Signalling Networks – Selection and Application Principles. Página de publicación oficial de la IEC.
- International Electrotechnical Commission, IEC 61643-41:2025, Low-Voltage Surge Protective Devices – Part 41: Surge Protective Devices Connected to DC Low-Voltage Power Systems – Requirements and Test Methods. Página de publicación oficial de la IEC.
- International Electrotechnical Commission, IEC 62236-4:2018, Railway Applications – Electromagnetic Compatibility – Part 4: Emission and Immunity of the Signalling and Telecommunications Apparatus. Página de publicación oficial de la IEC.
- International Electrotechnical Commission, IEC 62425:2025, Railway Applications – Communication, Signalling and Processing Systems – Safety-Related Electronic Systems for Signalling. Página de publicación oficial de la IEC.
- International Electrotechnical Commission, IEC 62498-3:2010, Railway Applications – Environmental Conditions for Equipment – Part 3: Equipment for Signalling and Telecommunications. Página de publicación oficial de la IEC.
- Australian Rail Industry Standards Organisation, AS 7708:2017, Signalling Earthing and Surge Protection. ARISO lists this standard as current. Official ARISO standard page.
- Transport for NSW, TS 05258:2.0, Common Signals and Control Systems Equipment Requirements, issue and effective date 23 June 2025. Official Transport for NSW PDF.
