Vietnam Register Department organizes a seminar, exchange, and answer-and-answer program on car emission inspection.
Speaking at the conference, Mr. Nguyen To An, Deputy Director of the Vietnam Register, said that previously the inspection was carried out according to the 90% rotation method.
However, this method does not fully evaluate. Therefore, the current method is applied to ensure more accurate car emission testing. This approach is being applied in many countries around the world.
Regarding this content, recently, on March 19, 2026, the Vietnam Automobile Transport Association issued a document proposing the process and method of measuring diesel engine emissions for motor vehicles in circulation.
Accordingly, the association proposes to change the method of fully accelerating to check car emissions.
Regarding the above proposal, the Vietnam Register said that it has responded, clearly stating the legal, practical and scientific basis of the free acceleration method (pulling the entire accelerator pedal journey).
According to the Vietnam Register, in Vietnam, emission inspection of road vehicles has been carried out since 1999 under Decision No. 1397/1999/QD-BGTVT dated June 11, 1999 on announcing the subjects and mandatory levels of applying 02 Vietnamese Standards on the environment for road vehicles.
The emission measurement method using the free acceleration cycle is specified in TCVN 5418:1991 Diesel engine car emissions - level and measurement method; TCVN 6438:1998 air quality - road traffic vehicle emissions - maximum permissible limit.
Before March 1, 2026, the method of measuring diesel engine smoke is specified in section 39, Part 2 of QCVN 122:2024/BGTVT, specifically: "Measuring smoke according to the free acceleration cycle specified in TCVN 7663".
From March 1, 2026, according to the provisions of QCVN 85:2025/BNNMT, the method of measuring the smoke level of exhaust fumes of cars with compressed engines is carried out by measuring exhaust samples according to the engine measuring cycle in free acceleration mode.
The engine measuring cycle in free acceleration mode is specified in section 9.4.2 of TCVN 7663:2007 (ISO 11614:1999) - progressive piston compression combustion internal combustion engine - smoke measuring device and determining the light absorption coefficient of exhaust gas.
Thus, the method of testing diesel engine emissions using the free acceleration cycle has been standardized by Vietnam into a standard since 1991.
Applied in the inspection of road motor vehicles for nearly 30 years.
This is the standard method in the world to assess the smoke absorption of diesel vehicles in circulation.
This method has been specified in: UNECE R24 Regulation of the United Nations; Directive 2014/45/EU of the European Union; Standard GB 3847-2018 of China. The International Automobile Inspection Organization (CITA) also has Recommendation No. 1 on vehicle inspection for grades M, N and O, which includes the method of measuring engine exhaust from compression by free acceleration cycle; ASEAN countries, Southeast Asia such as Malaysia, Indonesia... all implement the method of measuring engine exhaust from compression by free acceleration cycle.
Regarding engine manufacturing principles: The view that older generation diesel engines do not have speed limiting systems is inaccurate.
The characteristic of every diesel engine is speed control through the amount of fuel injected. Therefore, 100% of diesel engines (including using PE, VE mechanical high-pressure pumps manufactured from previous decades) must be equipped by the manufacturer with a Governor.
This accelerator has the task of automatically cutting fuel when the engine reaches the maximum design speed to protect the engine block. This maximum speed is completely within the safe tolerance of the material designed by the manufacturer.
The Vietnam Register expressed its desire for the association to propagate so that transport businesses can correctly understand the scientific and humane meaning of the new process.
We affirm that this process is not intended to cause difficulties but is the highest safety solution for vehicles and public health" - a representative of the Vietnam Register emphasized.
