ECE Regulation No. 39 sets forth the uniform provisions concerning the approval of vehicles with regard to their speedometer equipment. This regulation is essential for ensuring that vehicles are equipped with accurate and reliable speedometers, which contribute to road safety by providing drivers with precise information about their vehicle's speed.

The regulation specifies the technical standards for the construction, installation, and performance of speedometer equipment. Speedometers must be designed to accurately reflect the vehicle's speed under various operating conditions. The regulation mandates that the speedometer must be visible to the driver and easy to read, ensuring that drivers can monitor their speed effectively at all times.

To ensure compliance, the regulation outlines rigorous testing procedures. These tests include checks for accuracy under different speeds and environmental conditions such as temperature fluctuations and vibrations. Manufacturers must conduct these tests to demonstrate that their speedometer equipment meets the required standards. The regulation also includes provisions for the calibration and maintenance of speedometers to ensure their continued accuracy over the vehicle’s lifetime.

Regular inspection and maintenance of speedometer equipment are required to prevent inaccuracies due to wear and tear or tampering. The regulation provides guidelines for periodic checks and servicing to maintain the reliability and accuracy of the speedometers.

ECE Regulation No. 39 is part of a comprehensive set of safety standards developed by the UNECE (United Nations Economic Commission for Europe) to promote vehicle safety across member countries. By adhering to this regulation, manufacturers contribute to improving road safety by ensuring that drivers have accurate and reliable information about their vehicle's speed, thus promoting safer driving practices.

The TAT Lab in Iran is authorized to perform testing and certification for compliance with ECE Regulation No. 39. This includes conducting all necessary tests to ensure that speedometer equipment meets the specified standards. By performing these tests, TAT Lab helps enhance road safety in Iran by ensuring that vehicles are equipped with accurate and reliable speedometers.