What Changed
- The Environmental Protection Department developed the AIMER system using AI acoustic fingerprints to detect illegally modified vehicle exhausts, currently undergoing field trials.
- Vehicle noise complaints to the Transport Department and Environmental Protection Department reached 2,282 in 2023, 1,917 in 2024, and 2,534 in 2025.
- Failure to comply with a Vehicle Examination Order or failing vehicle inspection empowers the Transport Department to cancel the vehicle licence.
Vehicle owners, transport operators, legal professionals, and regulatory authorities in Hong Kong SAR are closely following developments regarding enforcement against excessive vehicle noise and illegal vehicle modifications. On November 4, 2026, the Secretary for Environment and Ecology, Mr Tse Chin-wan, provided a detailed written response to a Legislative Council question (LCQ21) asked by Dr Hon Chan Han-pan concerning the application of artificial intelligence to identify illegally modified exhausts causing noise nuisance. The response outlines Hong Kong SAR's statutory framework governing vehicle noise emissions, the operational status of the self-developed Artificial Intelligence on Modified Exhaust Recognition (AIMER) system, and statistical data regarding vehicle noise complaints and enforcement actions taken from 2023 through 2025.
### Legal and Statutory Framework Governing Vehicle Noise
In Hong Kong SAR, regulatory control over vehicle noise emissions and structural modifications relies on several statutory instruments under the laws of Hong Kong:
1. **Noise Control (Motor Vehicles) Regulation (Cap. 400I):** Under the Road Traffic Ordinance (Cap. 374) (RTO), motor vehicles are required at first registration to strictly comply with the noise emission standards stipulated in Cap. 400I.
2. **Road Traffic (Construction and Maintenance of Vehicles) Regulation (Cap. 374A):** This regulation mandates that vehicles propelled by internal combustion engines must be fitted with silencers maintained in good and efficient working order. Crucially, Cap. 374A prohibits the alteration or replacement of a silencer in any manner that increases the noise caused by the escape of exhaust gases.
3. **Enforcement and Inspection Powers:** Under the statutory framework, if a police officer reasonably suspects that a vehicle has been illegally modified, the officer is empowered to direct the vehicle to a vehicle examination centre for inspection by an authorized vehicle examiner. Concurrently, the Transport Department (TD) receives reports and referrals of suspected defective or illegally modified vehicles from the public and other government departments to take necessary follow-up actions.
### The Technical Development and Operation of the AIMER System
To enhance detection capabilities, the Environmental Protection Department (EPD) has developed the Artificial Intelligence on Modified Exhaust Recognition (AIMER) system in-house. AIMER aims to evaluate and verify the technical feasibility of utilizing artificial intelligence to automatically identify noise generated by illegally modified vehicles.
The AIMER system relies on specialized hardware equipment and data collection methodologies:
- **Hardware Integration:** The system deploys hardware components including acoustic microphones, infrared cameras, and laptop computers.
- **Acoustic Fingerprinting:** As vehicles pass by, AIMER captures acoustic data and converts the sounds into unique acoustic fingerprints.
- **AI Matching Model:** These acoustic fingerprints are compared against information stored in a central database using an AI model to detect vehicles suspected of having illegally modified exhaust pipes.
- **Field Data Collection:** The EPD collects sound data from various vehicle types at diverse locations, including illegal motor racing blackspots and areas frequently used by suspected modified vehicles, to analyze acoustic characteristics.
Currently, AIMER remains at a technical development and field trial stage. It undergoes ongoing model training, functional adjustments, and real-world testing. The government noted that performance requires further refinement, particularly in detecting less conspicuous suspected illegally modified exhaust pipes during nighttime hours. Suspected cases detected during field trials are referred by the EPD to relevant law enforcement agencies for appropriate follow-up.
### Enforcement Statistics and Complaint Trends (2023–2025)
The Secretary for Environment and Ecology presented data compiled from the Transport Department (TD) and the Environmental Protection Department (EPD) covering the three-year period from 2023 to 2025:
- **Total Vehicle Noise Complaints Received:**
- **2023:** 2,282 complaints
- **2024:** 1,917 complaints
- **2025:** 2,534 complaints
- **Complaints Involving Suspected Illegally Modified Vehicles:**
- **2023:** 1,701 cases
- **2024:** 1,170 cases
- **2025:** 1,428 cases
- **Vehicle Examination Orders Issued Resulting from Complaints:**
- **2023:** 592 orders issued
- **2024:** 412 orders issued
- **2025:** 459 orders issued
The official response noted that the Hong Kong Police Force does not maintain specific statistics on these relevant complaints and prosecutions.
### Practical Implications for Vehicle Owners and Licensing
The statutory framework carries direct consequences for vehicle owners:
- **Licence Cancellation Risk:** If a vehicle owner fails to comply with an issued Vehicle Examination Order, or if the vehicle fails the required examination at a centre, the Transport Department holds the statutory authority to cancel the vehicle licence.
- **Inter-Agency Coordination:** The Police, Transport Department, and Environmental Protection Department continuously exchange information regarding suspected modified vehicles and hotspots, strengthening reporting mechanisms to combat noise nuisances and illegal racing activities.
### Frequently Asked Questions
**Q1: What specific statutory regulations govern vehicle exhaust noise and silencers in Hong Kong SAR?**
A1: Motor vehicles must comply with noise emission standards in the Noise Control (Motor Vehicles) Regulation (Cap. 400I) upon first registration under Cap. 374. Additionally, the Road Traffic (Construction and Maintenance of Vehicles) Regulation (Cap. 374A) mandates that internal combustion engine vehicles have efficient silencers that must not be altered or replaced to increase exhaust noise.
**Q2: How does the AIMER system work to identify suspected illegally modified vehicles?**
A2: AIMER uses microphones, infrared cameras, and laptop computers to convert passing vehicle sounds into acoustic fingerprints. An AI model compares these fingerprints against a database to identify vehicles suspected of possessing illegally modified exhaust systems.
**Q3: Is the AIMER system fully operational for legal enforcement across Hong Kong SAR roads?**
A3: No. AIMER remains at a technical development stage, undergoing model training, functional adjustments, and field trials. The EPD is working to enhance its performance, especially for identifying less conspicuous modified exhausts at night, while referring detected cases to law enforcement.
**Q4: What consequences apply if a vehicle owner fails to comply with a Vehicle Examination Order?**
A4: If a vehicle owner fails to comply with a Vehicle Examination Order issued following a referral or inspection, or if the vehicle fails the examination, the Transport Department may cancel the vehicle licence.
Who May Be Affected
Vehicle owners, motor transport operators, legal practitioners, and law enforcement authorities in Hong Kong SAR.
Cross-Border Context
Not applicable; concerns local statutory traffic regulation and environmental noise enforcement within Hong Kong SAR.
What to check next
- Future official announcements from the Environmental Protection Department regarding statutory deployment of the AIMER system.
- Subsequent Legislative Council discussions on statutory enforcement mechanisms for motor vehicle noise controls.
This article provides general information and does not constitute legal advice. Consult the official text and obtain advice appropriate to your circumstances where needed.