EN 50556 Road Traffic Signal Systems

The European standard "EN 50556 Road traffic signal systems" describes the requirements for road traffic signal systems, including their development, design, testing, installation and maintenance. This standard is the electrotechnical part of two standards published by the European Committee for Standardization (CEN), in particular:

• EN 12368 Traffic control equipment - Signal heads
• EN 12675 Traffic signal controllers - Functional safety requirements

Each of these standards is used alone or in conjunction with this standard to describe an operational piece of equipment or system. This is achieved using the electrotechnical methods and tests defined in this standard.

Where road traffic signal systems are to be used in conjunction with other systems, for example public lighting or railway signalling and communications, this standard is used in conjunction with other relevant standards for other associated systems to ensure that overall safety is not compromised.

This standard applies to permanent and temporarily installed traffic signal control equipment and portable traffic control equipment, except for portable traffic signal equipment that can only control alternate/shuttle operating lanes.

For the purposes of this standard, the following definitions also apply:

• Road traffic signal systems refer to systems for safely controlling traffic flow at intersections, pedestrian crossings and other places where there is conflicting traffic using light signals. These may consist mainly of the following elements:
  • Controllers
  • Signal heads, signal devices and traffic signs (e.g. signal heads for traffic signals, acoustic signal generators, mechanical signal generators and traffic signs connected to the road traffic signal system)
  • Traffic sensors and detectors (e.g. request push buttons, vehicle detectors or pedestrian detectors)
  • Monitoring equipment (e.g. photographic monitoring devices)
  • Equipment enclosures
  • Electricity supply
  • Kablolar
  • Links
  • supports
• Failure mode analysis is a method of examining all failure modes to ensure that signal states that endanger road users or the risk of electrical hazards cannot occur during the normal operating conditions of a road traffic signal system or, if they occur as a result of or in the presence of a fault, signal states that endanger road users can be detected and prevented from continuing.
• Signal protection facility refers to facilities that aim to prevent signal situations that endanger traffic.
• Monitoring element refers to the device that signals the electrical and mechanical states of the equipment, preferably for signal circuits, and converts the obtained information so that it can be processed in signal protection facilities.
• Equipment refers to the complete road traffic signal system or part thereof.
• Hardware failure refers to component failures and any effect that will cause equipment failure. Systematic hardware failures constitute design failures or systematic manufacturing failures.
• Software refers to all or part of the sequential instructions for a road traffic signal system, including associated documentation. Software is not subject to any wear and tear or failure mechanism. Once implemented, the software itself cannot be tampered with.
• A software error refers to a deviation between the realized and intended functional contents of the software. All errors in the software are systematic errors.
• Controllers (traffic) refer to electrical devices that control signals.
• Signal group refers to the set of conditions applied to a group of signal heads that always receive the same signal light indications.
• Operating system refers to the principle software that enables a computer to operate and determines the fundamentals, protocols, and functions that involve communicating with the computer's internal and external resources.

Among the numerous testing, measurement, analysis and evaluation studies carried out for businesses in various sectors, our organization also provides testing services defined in the "EN 50556 Road traffic signal systems" standard with its trained and expert staff and advanced technological equipment.