ISO 16508:1999 PDF

Overview

ISO 16508:1999 – Road traffic lights - Photometric properties of 200 mm roundel signals – is an international standard developed by ISO and CIE (International Commission on Illumination). This standard specifies essential photometric requirements for 200 mm diameter roundel road traffic signals, focusing on their visibility to ensure safe and effective traffic control. The primary aspects covered include the colour, luminous intensity, and luminous intensity distribution of traffic signal lights. Additionally, ISO 16508:1999 addresses the "sun phantom" effect, which can negatively influence the correct recognition of signal operation due to sunlight reflection.

Key Topics

• Luminous Intensity and Distribution: Specifies minimum and recommended intensity values for daytime and nighttime operation, ensuring signals are visible under diverse lighting and environmental conditions.
• Colour Specification: References CIE standards for the colours red, yellow, and green, crucial for universal recognition and compliance.
• Uniformity of Luminance: Requires uniform brightness across the roundel’s whole surface, eliminating abrupt changes that may hinder visibility or correct driver interpretation.
• Sun Phantom Prevention: Addresses the problem of false signal appearance caused by sunlight reflections (“sun phantom”). Defines minimum ratios between real and phantom signal intensity to prevent confusion.
• Background Screens and Visors: Recommends the use of background screens and visors to enhance signal contrast and reduce the influence of ambient light such as direct sunlight.
• Testing and Measurement Methods: Outlines procedures for verifying compliance, including specific measurements for intensity, distribution, and phantom light luminance ratio.

Applications

ISO 16508:1999 is essential for:

• Traffic Signal Manufacturers: Guiding the design and testing of compliant 200 mm roundel signals for both new installations and replacements.
• Road Authorities and Urban Planners: Ensuring the installed signals meet international safety and visibility requirements, particularly at intersections, pedestrian crossings, and on road networks where traffic safety is paramount.
• Testing Laboratories: Standardizing photometric assessment methods for road signal light performance, allowing consistent certification and quality assurance.
• Regulatory Compliance: Assisting municipalities and transportation agencies in meeting global safety norms and integrating with other international standards related to road signalization.
• Lighting Engineers: Informing the design and adjustment of illumination systems in urban and suburban roadway environments to avoid signal misinterpretation-especially important for high-speed or poorly lit locations.

Related Standards

For comprehensive implementation and understanding of signal light properties, ISO 16508:1999 references and complements several key standards:

• CIE 17.4: International Lighting Vocabulary – Standardized definitions for photometric terms.
• CIE 18.2: The Basis of Physical Photometry – Fundamentals of measuring light.
• CIE 38: Radiometric and Photometric Characteristics of Materials and Their Measurement
• CIE 48: Light Signals for Road Traffic Control – Broader guidance for light signals.
• CIE 79: A Guide for the Design of Road Traffic Lights – Previous recommendations replaced in part by ISO 16508.
• CIE 107: Review of the Official Recommendations for the Colours of Signal Lights
• CIE DS004.4: Colours of Light Signals – Chromaticity requirements for signal lights.

Practical Value

ISO 16508:1999 is a cornerstone for ensuring road traffic light visibility, standardization of photometric performance, and driver and pedestrian safety worldwide. Its practical application reduces the risk of accidents caused by misinterpretation of signals, mitigates sun phantom issues, and supports harmonization of traffic light systems in urban design and road safety projects.

Keywords: ISO 16508:1999, road traffic lights, photometric properties, luminous intensity, roundel signals, sun phantom, signal colour standards, traffic safety, CIE, traffic signal visibility.