UN ECE R138 tests cover a series of tests carried out in accordance with the relevant regulation for the evaluation of Silent Road Transport Vehicles in the categories specified in the regulation.
ECE regulations define cross-border technical regulations for establishing approval or uniform approval procedures for motor vehicles and motor vehicle parts. Automated commercial vehicles are already fully eligible for approval only through appropriate individual measures in the country in which they will be used. What is missing is a set of rules at the international ECE level.
Regulation 138 of the United Nations Economic Commission for Europe (UN/ECE) — Covers the uniform provisions for the approval of Silent Road Transport Vehicles with regard to their reduced audibility and the tests applied accordingly.
This Regulation applies to electric vehicles of categories M and N, which can move audibly in normal mode, in reverse or at least one forward gear, without starting the combustion engine. Electric vehicle means a vehicle with a drivetrain comprising at least one electric motor or electric motor generator.
The acoustic characteristics, the sound emitted by the type of vehicle submitted for approval, will be measured by the methods described in the regulation. The speed range for starting is greater than 0 km/h and up to 20 km/h.
If the vehicle not equipped with an AVAS meets the general levels specified with a margin of +3 dB(A), the specification and frequency shift for one-third octave bands do not apply. The test speeds for the constant speed tests approval are 10 km/h and 20 km/h.
A vehicle is exempt from this particular test if, after testing, it is tested 10 times in a row on a series of measurements without recording a valid measurement because the vehicle's internal combustion engine (ICE) remains active or restarts and interferes with the measurements.
Frequency shift is tested to indicate acceleration and deceleration. The purpose of frequency shift is to inform road users acoustically about the change in vehicle speed.
When tested under the conditions specified in the regulation, at least one tone in the specified frequency range emitted by the vehicle will vary on average by at least 0,8% in proportion to the speed in each gear ratio.
Within the scope of the regulation, many mechanical, dynamic and environmental tests are carried out as well as measurements for the approval of the relevant equipment. For tests to be considered successful, test results must meet regulatory requirements.
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