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Smoke and exhaust-noise rules for vehicles in use

Singapore’s rules for smoke and visible vapour from vehicles on roads, in-use exhaust-noise standards, NEA enforcement and reporting.

vehicle-emissions exhaust-smoke vehicle-noise NEA

Primary source: https://sso.agc.gov.sg/SL/EPMA1999-RG6?ProvIds=pr19-%2Cpr20-%2Cpr23-

Smoke and exhaust-noise rules for vehicles in use

Singapore regulates smoke and exhaust noise from vehicles while they are in use on roads. These operating rules are separate from the registration incentives for cleaner vehicles covered in vehicle-emissions-and-cleaner-vehicle-incentives (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, regs. 6–7 and 19–20).

Smoke and visible vapour

Regulation 19 prohibits using, or causing or permitting the use on a road of, a motor vehicle that emits smoke or visible vapour. The driver commits an offence; if the driver is not the vehicle’s owner, the owner also commits an offence. The Fifth Schedule separately states that a motor vehicle must not emit smoke or visible vapour while in use (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, reg. 19 and Fifth Schedule).

Regulation 6 applies the Fifth Schedule to every licensed motor vehicle in use and every motor vehicle not registered in Singapore that is in use. The petrol-car and two-wheeled motorcycle rows below are expressly based on Singapore registration dates. They do not replace checking the full schedule for a vehicle’s registration and vehicle type (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, reg. 6 and Fifth Schedule).

For petrol-driven cars other than motorcycles and scooters registered in Singapore, the Fifth Schedule sets these idle-speed limits:

Singapore registration period Carbon monoxide (CO) Hydrocarbons (HC)
Before 1 October 1986 6.0% 1,200 ppm
1 October 1986 to before 1 July 1992 4.5% 1,200 ppm
1 July 1992 to before 1 January 2001 3.5% 1,200 ppm
1 January 2001 to before 1 April 2014 1.0% 300 ppm
On or after 1 April 2014 0.5% No limit

For petrol cars registered in Singapore on or after 1 April 2014, the schedule also sets high-idle limits of 0.3% CO and 200 ppm HC, and lambda must be within 3% of 1.00. “High idle speed” means at least 2,000 revolutions per minute for a stationary vehicle. Diesel vehicles in use must not emit smoke with opacity above 40 Hartridge Smoke Units (HSU) or its equivalent (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, Fifth Schedule).

For a Singapore-registered two-wheeled motorcycle or scooter, the Fifth Schedule sets idle limits of 4.5% CO and 7,800 ppm HC for a 2-stroke engine or 2,000 ppm for a 4-stroke engine if registered before 1 October 2014; for one registered on or after that date, the limits are 3.0% CO and 1,000 ppm HC. Separately, regulation 19A makes it an offence to use most two- or three-wheeled motorcycles and scooters (whether or not registered in Singapore) if idle emissions exceed 4.5% CO, 7,800 ppm HC for a 2-stroke engine, or 2,000 ppm HC for a 4-stroke engine. Regulation 19A excludes classic, normal vintage, restricted vintage and revised use vintage vehicles (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, reg. 19A and Fifth Schedule).

NEA says owners of smoky vehicles may be required to send them for smoke-emission inspection at an authorised vehicle inspection centre. If a vehicle fails, the owner is fined and must rectify it and pass a re-inspection before it is allowed back on the road. On conviction, the maximum fine under the Regulations is $2,000 for a first offence and $5,000 for a second or subsequent offence (NEA, Air Pollution Regulations; Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, reg. 23).

The Fifth Schedule sets idle limits for Singapore-registered three-wheeled motorcycles and scooters at 4.5% CO and 7,800 ppm HC for a 2-stroke engine or 2,000 ppm HC for a 4-stroke engine. For petrol cars, motorcycles and scooters registered as classic or vintage vehicles, the separate limits use the vehicle’s original first registration date, rather than its Singapore registration date:

Vehicle type and original first registration date CO at idle HC at idle
Petrol car, before 1 October 1986 6.0% No limit
Petrol car, 1 October 1986 to before 1 July 1992 4.5% No limit
Petrol car, 1 July 1992 to before 1 January 2001 3.5% No limit
Motorcycle or scooter, before 1 October 1986 6.0% No limit
Motorcycle or scooter, 1 October 1986 to before 1 July 2003 4.5% No limit

These separate rows apply to vehicles registered as classic, normal vintage, restricted vintage or revised use vintage vehicles. “Original first registration date” means the earliest first-registration date if the vehicle was first registered in more than one country, or its first-registration date if it was registered in only one country (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, Fifth Schedule).

Exhaust-noise standards

Regulation 20 makes it an offence to use, cause or permit the use on a road of a motor vehicle that does not meet the exhaust-noise standard for its class. The in-use standards apply to motor vehicles whether registered in Singapore or elsewhere. Most follow the Sixth Schedule; a licensed motor vehicle registered before 1 July 1999 follows the Seventh Schedule (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, regs. 7 and 20, Sixth and Seventh Schedules).

For most in-use vehicles, the Sixth Schedule measures noise 0.5 metre from the open end of the exhaust pipe. It sets these limits:

Vehicle and registration Limit
Two-wheeled motorcycle or scooter registered in Singapore on or after 1 April 2023 5 dB(A) above its reference value
Two-wheeled motorcycle or scooter registered earlier in Singapore, or registered elsewhere The higher of 99 dB(A) or 5 dB(A) above its reference value
Three-wheeled motorcycle or scooter registered in Singapore on or after 1 April 2023 5 dB(A) above its reference value
Three-wheeled motorcycle or scooter registered earlier in Singapore, or registered elsewhere The higher of 99 dB(A) or 5 dB(A) above its reference value
Car, taxi or station wagon registered in Singapore on or after 1 April 2023 5 dB(A) above its reference value
Car, taxi or station wagon registered earlier in Singapore, or registered elsewhere The higher of 103 dB(A) or 5 dB(A) above its reference value
Goods vehicle or bus, gross vehicle weight up to 3.5 tonnes, registered in Singapore before 1 April 2024 or registered elsewhere The higher of 103 dB(A) or 5 dB(A) above its reference value
Goods vehicle or bus, gross vehicle weight above 3.5 tonnes, registered in Singapore before 1 April 2024 or registered elsewhere The higher of 107 dB(A) or 5 dB(A) above its reference value
Goods vehicle or bus registered in Singapore on or after 1 April 2024 5 dB(A) above its reference value

The “reference value” is the stationary noise level accepted for the vehicle’s type approval in Singapore, or the qualifying manufacturer certificate or vehicle plate value for a vehicle registered elsewhere. A licensed vehicle registered before 1 July 1999 follows the Seventh Schedule instead (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, regs. 7 and 20, Sixth and Seventh Schedules).

NEA says an in-use vehicle that fails the prescribed noise standard at a mandatory periodic inspection at an authorised inspection centre will not have its road tax renewed and cannot be used on the road (NEA, Vehicular Noise Control).

Exhaust-system condition and modifications

For petrol-driven motor vehicles in use, the Fifth Schedule also requires a silencer, expansion chamber or other suitable and sufficient device to reduce exhaust noise, and requires all exhaust-system parts to be in good and sufficient condition and comply with the exhaust requirements. Separately, rule 106 of the Road Traffic (Motor Vehicles, Construction and Use) Rules makes it an offence to use on a road an internal-combustion vehicle with an exhaust system that is not approved for use by the Registrar, is not in good and efficient working order, or has been modified in a way likely to prevent it from working properly or efficiently. Rule 106 defines the exhaust system to include a silencer, expansion chamber, exhaust pipe or another device used to expel exhaust gases (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, Fifth Schedule; Singapore Statutes Online, Road Traffic (Motor Vehicles, Construction and Use) Rules, rule 106).

LTA requires approval before an exhaust system is replaced or changed. Its evaluation checklist asks for the product manufacturer’s certification that the aftermarket system suits the vehicle’s make and model, and test reports from an LTA- or NEA-recognised laboratory showing compliance with that model’s noise and exhaust-emission standards. LTA says catalytic converters and mufflers must not be removed; for motorcycles, the exhaust silencer or dB killer must not be removed. LTA describes exhaust-system alteration as a major modification under the vehicle-registration rules (LTA, Vehicle Technologies and Modifications; Singapore Statutes Online, Road Traffic (Motor Vehicles, Registration and Licensing) Rules, rule 12B).

For the Singapore-registered classes listed below, the Sixth Schedule sets a separate standard for the replacement silencing system when a major modification alters the exhaust system. The listed alternatives are technical approval standards; they are separate from the general in-use noise limits measured at the exhaust outlet above (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, Sixth Schedule):

Vehicle class and Singapore registration date Alternative replacement-silencer standards listed in the Sixth Schedule
Two- or three-wheeled motorcycle or scooter, before 1 April 2023 UN Regulation No. 92 (Revision 1, Amendment 2, incorporating the 01 series); Directive 97/24/EC; Regulation (EU) No. 168/2013; or Japan’s Automobile Type Approval Handbook, Blue Book 11-3-112, Attachment 112
Two-wheeled motorcycle or scooter, on or after 1 April 2023 UN Regulation No. 92 (Revision 1, Amendment 2, incorporating the 01 series); Regulation (EU) No. 168/2013 read with Commission Delegated Regulation (EU) No. 134/2014; or Japan’s Blue Book 11-3-112, Attachment 112, Section II
Three-wheeled motorcycle or scooter, on or after 1 April 2023 UN Regulation No. 92 (Revision 1, Amendment 2, incorporating the 01 series); Directive 97/24/EC; Regulation (EU) No. 168/2013 read with Commission Delegated Regulation (EU) No. 134/2014; or Japan’s Blue Book 11-3-112, Attachment 112
Car, taxi or station wagon, before 1 April 2023 UN Regulation No. 59 (Revision 1, 01 series, or Revision 2, 02 series); Directive 70/157/EEC as last amended by Directive 96/20/EC; Regulation (EU) No. 540/2014; or Japan’s Blue Book 11-3-112, Attachment 112
Car, taxi or station wagon, on or after 1 April 2023 UN Regulation No. 59 (Revision 2, 02 series); Regulation (EU) No. 540/2014; or Japan’s Blue Book 11-3-112, Attachment 112, Section II
Goods vehicle or bus, before 1 April 2024 UN Regulation No. 59 (Revision 1, 01 series, or Revision 2, 02 series); Directive 70/157/EEC as last amended by Directive 96/20/EC; Regulation (EU) No. 540/2014; or Japan’s Blue Book 11-3-112, Attachment 112
Goods vehicle or bus, on or after 1 April 2024 UN Regulation No. 59 (Revision 2, 02 series); Regulation (EU) No. 540/2014; or Japan’s Blue Book 11-3-112, Attachment 112, Section II

For a licensed vehicle registered before 1 July 1999, the Seventh Schedule measures noise 0.5 metre from the open end of the exhaust pipe and sets these limits:

Vehicle class Limit
Motorcycle, scooter or trivan The higher of 106 dB(A) or 5 dB(A) above the vehicle’s reference value
Motor car, taxi or station wagon The higher of 105 dB(A) or 5 dB(A) above the vehicle’s reference value
Light goods vehicle The higher of 109 dB(A) or 5 dB(A) above the vehicle’s reference value

For this Schedule, a light goods vehicle is generally a goods vehicle with maximum laden weight not exceeding 3 metric tons and a certificate of entitlement issued before 1 July 1999, or not exceeding 3.5 metric tons and a certificate issued on or after that date. The definition excludes listed specialist vehicles, including construction equipment, engineering plant, recovery vehicles, mobile canteens or banks, and vehicles for specific purposes such as horse floats. The Schedule defines the reference value by reference to the stationary noise level in the type-approval documents accepted by the Registrar of Vehicles (Singapore Statutes Online, Environmental Protection and Management (Vehicular Emissions) Regulations, Seventh Schedule).

Maintenance and reporting

NEA advises owners to maintain vehicles in good condition, use the correct gear and avoid overloading to help prevent smoke emission. For two-stroke motorcycles, it advises following the manufacturer’s recommended fuel-to-lubricant mix or using a higher-grade smoke-free lubricant (NEA, Air Pollution Regulations).

People who spot a smoky vehicle or an idling engine can report it to NEA through the online feedback form or MyENV app. NEA asks for details such as the vehicle registration number, location, date and time. The separate idling rule and its exceptions are covered in eco-driving-in-singapore (NEA, Air Pollution Regulations).

Coverage debt

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