LCQ21: Artificial Intelligence on Modified Exhaust Recognition system
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Question:
I have consistently expressed concern about the problem of noise nuisance caused by illegally modified vehicles while in operation. It is learnt that the Environmental Protection Department's self-developed Artificial Intelligence on Modified Exhaust Recognition (AIMER) system has been able to successfully identify illegally modified vehicles. In this connection, will the Government inform this Council:
(1) whether, over the past three years, the authorities have grasped (i) the number of complaints relating to vehicle noise; (ii) the number of cases involving illegally modified vehicles; and (iii) among such cases, the number of those in respect of which prosecutions were instituted; if so, of the breakdown of the figures; if not, the reasons for that;
(2) whether the authorities have investigated and analysed the correlation between illegally modified vehicles and excessive noise emitted by vehicles, as well as the relevant testing methods, so as to facilitate the detection and identification of modified vehicles emitting excessive noise on the roads; if so, of the details; if not, the reasons for that;
(3) whether, since the development of the AIMER system, the authorities have deployed the AIMER system on expressways or trunk roads to detect illegally modified vehicles; if so, of the details and the specific arrangements; if not, the reasons for that; and
(4) given that illegal motor racing activities also cause serious noise nuisance, whether the authorities have deployed the AIMER system at illegal motor racing blackspots to assist with combating and enforcement operations; if so, of the respective details (including the number of operations carried out, their locations, and the number of successful prosecutions); if not, the reasons for that?
Reply:
President,
Having consulted the Hong Kong Police Force (Police) and the Transport Department (TD), my consolidated response to the question raised by the Dr Hon Chan Han-pan is as follows:
In accordance with the Road Traffic Ordinance (Cap. 374) (RTO), motor vehicles are required, at first registration, to comply with the noise emission standards stipulated in the Noise Control (Motor Vehicles) Regulation (Cap. 400I). In addition, the Road Traffic (Construction and Maintenance of Vehicles) Regulation (Cap. 374A) stipulates that vehicles propelled by internal combustion engine are required to be fitted with silencers maintained in good and efficient working order, and that a silencer shall not be altered or replaced in such a way that the noise caused by the escape of the exhaust gases is made greater. If a police officer reasonably suspects that a vehicle has been illegally modified, he may direct the vehicle to a vehicle examination centre for inspection by a vehicle examiner. To safeguard the safety of road users, the TD would receive reports or referral of suspected defective vehicles (including suspected illegally modified vehicles) from the public and other Government departments, and would take follow-up actions to the suspected defective vehicles.
With regard to noise control considerations, the Environmental Protection Department (EPD) has been closely monitoring the technological developments in identifying excessive noise emitted from modified vehicles. The Artificial Intelligence on Modified Exhaust Recognition (AIMER) was developed in-house by the EPD, aiming to assess and verify the feasibility of utilising AI to identify noise emitted by illegally modified vehicles. At present, AIMER remains at a technical development stage. The EPD will maintain close liaison with the TD and the Police to continuously enhance AIMER and its applications. In addition, the Police, the TD, and the EPD have been exchanging information from time to time on suspected illegally modified vehicles and relevant hotspots, and strengthening the existing reporting mechanism to combat activities involving illegally modified vehicles.
(1) The breakdown of complaints about vehicle noise received by the TD and the EPD over the past three years is set out below. Of these complaints, the table also shows those reported to involve illegally modified vehicles and among the latter, those resulting in the issuance of Vehicle Examination Orders.
| Year | 2023 | 2024 | 2025 |
| Total complaints about vehicle noise received by the TD and the EPD | 2 282 | 1 917 | 2 534 |
| Of which, complaints reported to involve illegally modified vehicles | 1 701 | 1 170 | 1 428 |
| Of the above, complaints resulting in the issuance of Vehicle Examination Orders | 592 | 412 | 459 |
If the owner of a vehicle fails to comply with a Vehicle Examination Order or if the vehicle fails an examination, the TD may cancel the vehicle licence of the concerned vehicle. In addition, the Police does not maintain statistics on the relevant complaints and prosecutions.
(2) to (4) The EPD collects acoustic data from various types of vehicles, including suspected illegally modified vehicles, at different locations frequented by such vehicles, including illegal motor racing blackspots, and analyses their acoustic characteristics. AIMER uses hardware such as microphones, infrared cameras, and laptop computers to convert the sounds of passing vehicles into acoustic fingerprints. These fingerprints are compared with information in a database using an AI model to identify vehicles suspected of having illegally modified exhaust pipes. AIMER is currently undergoing model training, functional adjustments, and field trials, with its performance still requiring further enhancement, particularly in identifying less conspicuous suspected illegally modified exhaust pipes during night time. The EPD has referred suspected cases identified during field trials to the relevant law enforcement departments for follow-up. Moving forward, the EPD will continue to enhance AIMER and maintain close liaison with the TD and the Police to strengthen collaboration to combat noise nuisance caused by illegally modified vehicles.
Ends/Wednesday, November 4, 2026
Issued at HKT 11:50
Issued at HKT 11:50
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