The railway sector has a series of requirements that must be taken into account when designing hardware for this environment.
Specifically, the European standard EN 50155 defines the requirements that electronic equipment installed on board railway rolling stock must meet. It is not only a technical requirement, but also a guarantee of reliability, safety, and durability in the harsh conditions that exist in this field. Compliance with this standard involves designing with the robustness, maintainability, and functional safety of the system in mind.
Equipment covered by EN 50155
EN 50155 applies to all electronic equipment on board rolling stock (trains, trams, and subways). The following table shows the different categories with examples of each:
EN 50155 – Equipment summary
| Category | Examples | Comments |
|---|---|---|
|
Control & Monitoring Systems |
Sensors, brake control, traction system, door control, HVAC |
Electronic systems for train control, monitoring, and automated operation |
|
Operator & Comfort Systems |
Electrically adjustable seats, air conditioning, Wi-Fi |
Electronics for driver comfort and passenger amenities |
|
Communication & Signaling Systems |
Signals, intercom systems, audiovisual systems |
Critical electronics for onboard communication and signaling |
|
Power Systems |
Battery chargers, power supplies, distribution panels |
Systems for onboard electrical supply and conditioning |
|
Monitoring & Diagnostics Systems |
Ethernet Train Backbone (ETB), MVB, IoT interfaces |
Equipment for train network communications, monitoring, and diagnostics |
|
Safety & Security Systems |
CCTV, monitoring systems, alarm systems |
Equipment for onboard security, passenger monitoring, and operational safety |
|
Operator Interface / Control Systems |
Driver control panels, driver consoles |
Electronics for train operation and control |
EN 50155 requirements
The standard classifies equipment according to environmental, electrical, and electromagnetic parameters, defining acceptable operating limits.
Designing in compliance with these specifications means ensuring that the equipment functions correctly in real conditions: voltage variations, continuous vibrations, electrical spikes, or sudden temperature changes.
The following tables summarize all these requirements:
EN 50155 – Environmental Requirements
| Test | Basic Standard | Test Specification |
|---|---|---|
|
Altitude |
EN 50155 |
A1: ≤ 1400 m |
|
Operating Temperature |
EN 50155 |
OT1: –25 °C to +55 °C |
|
Mechanical Vibration |
EN 50155 |
Cat. 1: 0.5 – 5.72 m/s² rms (5–150 Hz) |
|
Mechanical Shock |
EN 50155 |
Cat. 1: 30 m/s², 11 ms, half-sine |
|
Humidity |
EN 50155 |
95 % RH @ +25 °C to +55 ºC; 24 h |
|
Dust & Water Ingress |
EN 50155 |
Protected: IP54 |
|
Salt Mist |
EN 50155 |
5 g/l NaCl @ +35 °C; 2h |
|
Flamability |
EN 45545-2 |
HL1: Basic (≈ UL 94 V-2) |
|
Reliability |
EN 50155 |
24 h at 55 °C under full load |
EN 50155 – Electrical Requirements
| Nominal Voltage (Vn) | Permanent Range (0,7 – 1,25 Vn) | Brownout (0,6 Vn @ 100 ms) | Transient (1,4 Vn @ 1 s) | Inrush Current | Power Interrupt | Insulation (50 Hz @ 1 min) | Direct Spikes (Line - Line & - Earth) | Polarity Reversal |
|---|---|---|---|---|---|---|---|---|
|
24 V |
16,6 - 30 V |
14,4 V |
33,6V |
Ip ≤ 1,5 × In |
S1: >0 ms |
500 V AC |
1,8 kV |
1 min (No damage) |
|
37,5 V |
26 - 47 V |
22,5 V |
52,5 V |
500 V AC |
||||
|
48 V |
33,6 - 60 V |
28,8 V |
67,2 V |
500 V AC |
||||
|
72 V |
50,4 - 90 V |
43,2 V |
100,8 V |
1.500 V AC |
||||
|
96 V |
67,2 - 120 V |
57,6 V |
134,4 V |
1.500 V AC |
||||
|
110 V |
77 - 137,5 V |
66 V |
154 V |
1.500 V AC |
EN 50155 – Electromagnetic Requirements (EN 50121-3-2)
| Phenomena | Basic Standard | Test Specification | Criterion |
|---|---|---|---|
|
Emission |
|||
|
Conducted RF Disturbances |
EN 55011 |
QP: 79 dBµV +20 dB (0,15 – 0,5 MHz) |
|
|
Radiated RF Electromagnetic Field |
EN 55011
(CISPR 11 Class A) |
QP: 40 dBµV/m (30 – 80 MHz) |
|
|
Inmunity |
|||
|
Electrostatic Discharge (ESD) |
EN 61000-4-2 |
± 6 kV (Contact) |
B |
|
Radiated RF Electromagnetic Field |
EN 61000-4-3 |
20 V/m @ 80% AM; 1 kHz (80 – 1.000 MHz) |
A |
|
Electrical Fast Transients (EFT/Burst) |
EN 61000-4-4 |
± 2 kV @ 5/50 ns; 5 kHz (Power Lines) |
B |
|
Surge (Slow Transient Overvoltage) |
EN 61000-4-5 |
± 1 kV @ 1,2/50 µs; 42 Ω (Line-Line) |
B |
|
Conducted RF Disturbances |
EN 61000-4-6 |
10 Vrms @ 80% AM; 1 kHz (0,15 – 80 MHz) |
A |
|
Power-Frequency Magnetic Field |
EN 61000-4-8 |
300 A/m @ 50 Hz |
A |
|
Damped Oscillatory Magnetic Field |
EN 61000-4-10 |
100 A/m @ 1 MHz & 10 MHz |
A/B |
|
Voltage Dips & Interruptions |
EN 61000-4-11 |
30% dip (0,1 s) |
B |
|
Oscillatory Wave (Common-Mode Transient) |
EN 61000-4-12 |
2.5 kV @ 1 MHz & 10 MHz (Common Mode) 1 kV @ 1 MHz & 10 MHz (Differential Mode) |
A/B |
Operating criteria:
- Criterion A: The equipment must work properly during and after the disturbance without any degradation or loss of functions or changes to stored data.
- Criterion B: The equipment may temporarily degrade during the disturbance, but it must continue to work properly after the disturbance without losing data.
- Criterion C: Temporary loss of function is permitted, but the equipment must restart automatically or manually as agreed, without loss of data.
RAMS: Reliability, Availability, Manteinability and Safety
The RAMS approach, defined by standard EN 50126, is essential to ensuring the overall performance of the railway system. It is not just a matter of complying with a standard, but of designing with reliability as a tangible objective.
EN 50155 – RAMS (EN 50126)
| RAMS Element | Definition |
|---|---|
|
Reliability (R) |
Probability that a system performs its intended function without failure over a specified period under specified conditions. |
|
Availability (A) |
Proportion of time a system is operational and capable of performing its function. |
|
Maintainability (M) |
Ease, accuracy, and speed with which maintenance can be performed. |
|
Safety (S) |
Ability of a system to operate without causing unacceptable risk to people, environment, or equipment. |
Designing with a RAMS approach from the outset reduces costs throughout the entire life cycle (LCC) and increases operator and end-user satisfaction, minimizing failures and making the device easier to maintain and safer.
SIL: Functional Safety
Safety Integrity Levels (SIL), defined by EN 50129 and IEC 61508, determine the degree of risk reduction required for a safety function.
EN 50155 – SIL (EN 50129, IEC 61508)
| SIL Level | PFD Low-Demand Mode | PFH High-Demand / Continuous Mode | Typical Description / Risk Reduction |
|---|---|---|---|
|
SIL 1 |
≥ 10⁻² to < 10⁻¹ |
≥ 10⁻⁶ to < 10⁻⁵ per hour |
Basic safety; low risk reduction.
Suitable for non-critical safety functions like illumination. |
|
SIL 2 |
≥ 10⁻³ to < 10⁻² |
≥ 10⁻⁷ to < 10⁻⁶ per hour |
Moderate safety; medium risk reduction.
Often used for moderately critical railway systems like door control. |
|
SIL 3 |
≥ 10⁻⁴ to < 10⁻³ |
≥ 10⁻⁸ to < 10⁻⁷ per hour |
High safety; high risk reduction.
Required for life-critical systems like signalling interlocks or automatic train protection. |
|
SIL 4 |
≥ 10⁻⁵ to < 10⁻⁴ |
≥ 10⁻⁹ to < 10⁻⁸ per hour |
Very high safety; very high risk reduction.
Extremely rare in railway applications, usually only theoretical in rail context. |
Correctly defining the SIL level avoids cost overruns and ensures that each function is developed with the appropriate rigor in design, verification, and validation.
Design in accordance with EN 50155: from theory to practice
Designing equipment in accordance with EN 50155 involves integrating concepts of robustness, safety, and reliability from the outset. Some real-world examples show how this standard has a positive impact on performance:
- CCTV systems designed for OT2 class with EMC filtering and surge suppression reduce field failures by up to 30%.
- Control gateways redesigned to comply with EN 50155 improve operational availability and reduce electrical incidents.
- Certified DC/DC converters increase their service life by optimizing heat dissipation and vibration resistance.
The value of a technical partner with experience in EN 50155
Selecting a supplier with expertise in EN 50155, RAMS, and SIL ensures technical compliance, reduces the risk of failure, speeds up certification, and improves project profitability. An experienced partner provides:
- Lower technical and regulatory risk
- Design optimized for the onboard railway environment
- Complete documentation and traceability
- After-sales support with remote diagnostics and modular spare parts
- Faster integration into the value chain
Conclusion
Compliance with EN 50155 is not an end goal, but rather the starting point for robust and competitive design. The combination of a solid regulatory approach, RAMS-oriented design, and SIL functional safety allows for the development of electronic equipment that offers reliability, sustainability, and long-term value. Companies that adopt this approach demonstrate technical expertise and foresight: reliability becomes a tangible competitive advantage.
At TEKHNE, we have more than 15 years of experience designing railway electronic hardware, and we accompany our clients throughout the entire process: from ideation and design to pre-certification, industrialization, and market launch, avoiding the risk of non-compliance in this sector where the requirements are significantly higher than in others.
