VSI 19 - Modifying seats or seating capacity

Published: February 2026.

VSI 19 – Modifying seats or seating capacity (PDF) is the official guideline made under the Road Safety (Vehicles) Regulations 2021.

The content on this page is reproduced from the official guideline. While every effort has been made to ensure consistency, the official guideline must be referenced for approved content.

This information sheet applies to vehicles 4.5 tonne GVM or less and excludes motorcycles. For heavy vehicle requirements please refer to the National Heavy Vehicle Regulator website.

Introduction

Regulation 35 of the Road Safety (Vehicles) Regulations 2021 (the Regulations) requires all modifications to a vehicle to either have specific approval from the Secretary to the Department of Transport and Planning (the Secretary) or to be carried out in accordance with guidelines published by the Secretary.

This information sheet is a published guideline by the Department of Transport and Planning for the purposes of Regulation 9 of the Regulations.

Fitting additional or replacement seats or removing seats is a modification and may require a Vehicle Assessment Signatory Scheme (VASS) approval certificate.

A list of VASS signatories authorised to issue approval certificates is available at the top of the VASS approval certificate page. It's also available from any VicRoads Customer Service Centre.

Seating categories

Seats are divided into three categories to allow them to be designed for occupants of different size and mass.

Category 1

Seats capable of being used by adults. Category 1 seats contribute to the seating description of a vehicle.

Category 2

Seats suitable for children approximately 4 to 12 years of age and capable of accommodating a child restraint.

Category 3

Seats suitable for children approximately 4 to 7 years of age and not capable of accommodating a child restraint.

Category 2 and 3 seats may have shoulder height markers on the seat which identify whether the seat is suitable for an occupant. If a person’s shoulder height is outside of the upper and lower range indicated on the seat, then it must not be used.

Where shoulder height markers are not present, a plate or label made of durable material identifying the seat category must be fitted in a conspicuous place on or near the additional seat.

Requirements for the design, construction, installation and removal of seats

Category 1 seats must comply with the relevant Australian Design Rules that apply to the vehicle the seats are intended to be installed in.

When a category 1 seat is permanently removed from a vehicle, the corresponding seat belt must also be removed.

Vehicle Standards Bulletin (VSB) 5 - Manufacture and Installation of Additional Seats, provides a nationally agreed set of requirements for the design, construction and installation of category 2 and 3 seats. VSB 5 is available on the Commonwealth Department of Infrastructure, Transport, Regional Development, Communication, Sport and the Arts (DITRDCSA) website.

Changing the ADR category of a vehicle

The Australian Design Rule (ADR) category of a vehicle defines the set of requirements that the vehicle must comply to under the ADRs. The ADR category of a vehicle is defined by the vehicle manufacturer using their specified mass ratings and rated occupant carrying capacities for that model of vehicle. A vehicle must comply to the applicable requirements of the ADR category to be considered compliant to the standards for registration.

Vehicle manufacturers may also provide a vehicle model where different specifications of that vehicle within the model range may be complied to different ADR categories (for example, lower specification variants of a vehicle model may be a NB1 ADR category and a higher specification variant of a vehicle model may be a MC ADR category).

The modification of a vehicle through the removal or addition of category 1 (adult) seats may change the vehicle’s listed ADR category. If different or additional ADRs apply to the vehicle’s new ADR category, it must comply with those ADRs. The vehicle must also continue to comply with the ADRs applicable to its original ADR category.

A Light Goods vehicle (category NA or NB1) fitted with additional seats may change to a Passenger vehicle (category MA, MB or MC) which may now require it to be subject to a different level of safety and compliance under the ADRs.

A Light Bus (category MD1-3) which has had seats removed may change to a Passenger vehicle category and be required to comply to a different level of safety and compliance under the ADRs.

For vehicles before first supply to market, modification of seating capacity or ADR category under the Second Stage of Manufacture (SSM) allowance is regulated by the DITRDCSA.

The modification of in-service vehicles is subject to the requirements of the Department of Transport and Planning’s Vehicle Assessment Signatory Scheme (VASS). It is recommended to consult a VASS signatory to understand if modifications to the seating capacity of your vehicle will result in a change of your vehicle’s ADR category.

For vehicles that are used for both the carrying of passengers and goods, the Australian Design Rules define the vehicle as being a passenger carrying vehicle when the total number of seating positions multiplied by 68kg is 50% or more of the vehicle’s load carrying capacity. Likewise, a passenger or omnibus becomes a goods carrying vehicle if the total number of seating positions multiplied by 68kg is less than 50% of the vehicle’s load carrying capacity.

Example

A passenger vehicle has a GVM of 2800 kg, an unladen mass of 2000 kg and has a Category 1 seating reduction from 7 to 3 seats.

Firstly, the ‘payload’, which is the weight a vehicle can carry without exceeding its GVM rating, must be calculated.

GVM of 2800 kg minus unladen mass of 2000 kg = 800 kg

This is the vehicle’s available ‘payload’ or total amount of weight the vehicle can transport without exceeding its GVM rating.

50% of this available payload = 400kg

Next, the total weight the vehicle must be able to carry for the seated occupants is calculated by multiplying each seating position by 68kg:

68 kg x 3 seats = 204 kg

When considering that 50% of the calculated payload is 400kg and the vehicle only requires an allocation of 204kg for passengers, this modified vehicle will now become a goods carrying vehicle, as it can carry more weight in goods than it can passengers.

This change in ADR category means the modified vehicle will require a VASS approval certificate.

Definitions related to vehicle ADR categories is available in the ADRs.

Prohibited modifications

Seats provided by the vehicle manufacturer that are fitted with integrated safety features such as seat belts, airbags, seat position sensors, or active head restraints play a key role in the vehicle’s compliance to the requirements of safety ADRs and must not be removed or replaced.

If seats fitted with integrated safety features need to be removed or replaced so that the vehicle can perform a specific function and/or accommodate a vehicle user – a VASS Signatory must be consulted, and conditional registration of the vehicle may be required.

Seats must not be installed in a rearward or side facing configuration unless it is required to support a specific function and/or accommodate a vehicle user – a VASS Signatory must be consulted, and conditional registration of the vehicle may be required.

A seating modification must not result in the safety of the vehicle being reduced from the level of safety provided by the vehicle manufacturer.

Seat modifications that require a VASS certificate

The following modifications for category 1 seats require approval and certification from a VASS signatory:

• installing additional seats;
• replacement of original seats with non-original seats;
• installing seats and seat belts in positions in the vehicle not provided by the vehicle manufacturer for that purpose;
• removing seats that result in the vehicle changing ADR categories (including the removal of seats as part of converting a vehicle to a motorhome - refer to VSI 5 – Conversion of vehicles to motor homes);
• reupholstering seats that incorporate an airbag; or
• modifying the original structure of a seat.

It's recommended that a VASS signatory be consulted prior to undertaking modifications to a vehicle to ensure they are carried out in an appropriate manner, and the vehicle will be able to be certified upon completion.

Seat modifications that don't require a VASS certificate

The replacement of category 1 seats doesn't require approval and certification from a VASS Signatory if all the following conditions are met:

• the category 1 seats were offered as an option for that vehicle by the vehicle manufacturer; and
• the category 1 seats are matched to corresponding seat belts, and both are installed to mounting positions provided by the vehicle manufacturer for that purpose; and
• the level of safety afforded to the occupants of the vehicle is not reduced.

The removal of category 1 seats does not require approval and certification from a VASS Signatory provided the vehicle’s ADR category does not change as a result of a reduction in seating capacity.

Temporary removal of seats

The temporary removal of category 1 seats, including quick release seats, does not require approval and certification from a VASS Signatory.

The removal of a category 1 seat will be considered temporary if the corresponding seat belt assembly for the affected seating positions remain in the vehicle (unless the seats have integrated seat belts).

The temporary removal of seats must not interfere with the vehicle’s supplementary restraint system (SRS), particularly for seats with integrated pretensioner seat belts. SRS circuits must continue to function without error warnings being displayed to the driver.

A passenger must not occupy a position in a vehicle where a seat has been temporarily removed and the vehicle is being used on the road network.

Note

Vehicle owners must be aware that, vehicles presenting for roadworthy, or VASS inspections must have temporarily removed seats refitted.

The removal of seats in conjunction with modifications or additions made to the vehicle that interfere with or prevent the seat from ever being reinstalled to its original condition is not considered a temporary removal of seats. For example, this could include the addition of a cargo barrier or redrilling the seat mounting holes.

Vehicles manufactured prior to 1969

Modifications to seats in vehicles manufactured prior to 1969 don't require VASS approval provided that the seat’s structure and mounting is at least that of the original seat. If there is any doubt about the seat mounting or structure, a VASS signatory should be consulted.

Although the vehicle does not require a VASS approval, the vehicle must continue to meet the requirements in the Road Safety (Vehicles) Regulations 2021.

Installation and removal of Category 2 and 3 seats

Seats in these categories must be fitted in accordance with the manufacturer’s instructions by a suitably qualified person. The seat must comply with the requirements of VSB 5 (alternatively, 5A and 5B) and once installed, be permanently affixed with manufacturer and installer plates in accordance with the corresponding VSB 5.

A VASS signatory should be consulted if instructions are not available, or if there is any doubt about the compliance of the installation, particularly if the seat being installed has been removed from another vehicle.

Notifying VicRoads when seats are added or removed

VicRoads must be notified when a category 1 (adult seat) is added or permanently removed from a vehicle.

Category 2 and 3 seats do not alter the seating description of the vehicle. Therefore, there is no need for the vehicle to be presented at a VicRoads Customer Service Centre to have the seating description upgraded.