Engineering Standards for LED Signal Modules Used in Wayside Signal Systems for the Quebec North Shore & Labrador Railway

TC E-16, September 2006

Table of Contents

  1. Purpose
  2. Definitions
  3. Relationship to other Applicable Engineering Standards
  4. Photometric Requirements
  5. Identification Requirements

1. Purpose

1.1 The purpose of this standard is to provide the minimum performance requirements for 200 mm Light Emitting Diode (LED) signal modules used in the railway signal and traffic control systems of the Quebec North Shore & Labrador Railway (QNS&L).

2. Definitions

AREMA: American Railway Engineering and Maintenance of Way Association (AREMA).

AREMA C&S Manual: Communications and Signals Manual of Recommended Practice produced by AREMA.

Candela (cd): SI unit of luminous intensity. The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 nm and that has a radiant intensity in that direction of 1/683 W per steradian (1 cd = 1 lm/sr).

Chromaticity: The colour of the light emitted by an LED signal module, specified as x-y or x and y chromaticity coordinates on the chromaticity diagram according to the 1931 Commission International d'Éclairage (CIE or International Commission on Illumination) Standard Observer and Coordinate System Railroad Signal Colors. The CIE is a professional organization recognized by the International Standards Organization (ISO) as an international standardization body regarding illumination.

LED Signal Module: An array of LEDs and a lens that together are capable of providing a circular signal indication, also referred to by AREMA as “LED Light Unit”.

Long Term Luminous Intensity Degradation: The reduction in luminous intensity that normally occurs when an LED is illuminated over an extended period of time.

Lumen (lm): SI unit of luminous flux. Luminous flux emitted in unit solid angle [steradian (sr)] by a uniform point source having a luminous intensity of 1 candela (1 lm = 1 cd x 1 sr).

Luminous Intensity (of a source in a given direction, Iv): The luminous flux dΦv leaving the source and propagating in the element of solid angle dΩ containing the given direction, divided by the element of solid angle (Iv = dΦv/dΩ candela).

Luminous Flux (Φv): Quantity derived from radiant flux Φe by evaluating the radiation according to its action upon the CIE standard photometric observer (lumen).

Signal: A means of conveying information.

Signal Indication: The information conveyed by a signal.

Wayside Signal System: In the context of these standards, it refers to a railway signal and traffic control system used to control train traffic.

3. Relationship to Other Applicable Engineering Standards

3.1 These engineering standards supplement, rather than replace, all other applicable engineering standards, including the Railway Signal & Traffic Control Systems Standards. However, in cases where these engineering standards conflict with other applicable engineering standards, these engineering standards will take precedence.

4. Photometric Requirements

Luminous Intensity

4.1 When LED signal modules are in use as part of a wayside signal system, they shall at all times and under all normal operational conditions (i.e., a temperature range of –40°C to 70°C) meet the minimum luminous intensity values shown in Table A-1.

Table A-1 Minimum Luminous Intensity (Candela) over its Lifetime (L: left, R: right)

Horizontal Spread (at 0° vertical angle) +3º L/R +6º L/R +8º L/R +10º L/R +11º L/R +12º L/R
Red 600 450 169 94 49 30 15
Yellow 1725 1275 375 131 86 68 49
Green 600 375 169 94 49 30 15

4.2 The signal indication displayed by the LED signal module must also be discernable at vertical angles up to 60° from the 0° horizontal axis.


4.3 A green or yellow LED signal module shall produce a light output that conforms to the chromaticity range defined in the AREMA C & S Manual, Part 7.1.10 (Recommended Design Criteria and Functional/Operational Guidelines for Signal Roundels, Lenses, Discs and Cones).

4.4. A red LED signal module shall produce a light output that conforms to the following chromaticity range:

  1. Maximum: y is not greater than 0.295, and,
  2. Minimum: y is not less than 0.998 - x.


4.5 The ratio of the greatest to the least luminance on the LED signal module shall not exceed 5:1, when measured over an average area of 500 mm2 of the LED signal module's light emitting surface.

5. Identification Requirements

5.1 The LED signal modules used by QNS&L shall meet these standards and be clearly labelled and identified with the following information:

Wayside LED Signal Module

  • Type: (single or multiple colours)
  • Colour(s): (red, green and/or yellow)
  • Beam Deflection Classification: (degrees)
  • Operating Voltage(s): (VDC or Vac)
  • Optimal Current at Operating Voltage(s): (mA)
  • Serial Number:
  • Date of Manufacture:
  • Applicable Transport Canada Engineering Standards:

5.2 If the LED signal module or its components require orientation, they shall be marked prominently and permanently with an indexing arrow.