Chassis and body modifications

Always consult with Vehicle Standards before attempting any modifications to a vehicle's body or chassis.

The chassis provides strength to support other vehicle components. It must absorb engine and driveline torque and endure shock from twisting on uneven road surfaces.

Chassis and body length

Lengthening or shortening a vehicle body is acceptable provided an engineer's report prepared by a Chartered Professional Engineer (438.4 KB PDF) is presented, certifying that the modified vehicle:

An MR620 Application to Modify a Motor Vehicle (891.8 KB PDF) is required for any chassis modification and a statement of requirements will be issued prior to the roadworthy inspection.

Wheel tubs

Fitting wheel tubs ie alterations to the inboard structure of the rear wheel housing, is acceptable provided that:

  • the modification does not weaken the vehicle's structure
  • there are no modifications to body structural members, chassis members or suspension mounting points and that there are no body modifications undertaken within 200 mm of any seat anchorage or seat belt anchorage.
    Alterations may be permitted provided that an engineering report prepared by a Chartered Professional Engineer is submitted demonstrating that the original strength has not been decreased.
  • wheels or tyres do not foul any part of the vehicle's suspension, brake lines or bodywork for the full range of suspension movement.


The upper body structure or roof of a passenger car contributes significantly to the total strength of the body of a monocoque construction vehicle and its removal can seriously affect the structural integrity of the original design of the vehicle.

There are no specific regulations under the Road Traffic Act 1961 that makes it an offence to remove the roof or upper body structure of a motor vehicle.  However, in the case of passenger cars and passenger car derivatives manufactured on or after 1 January 1969, the removal of a vehicle roof may interfere with the Australian Design Rule 5a,  ADR 5b or ADR 5/00, relating to the upper seat belt anchorages.

Consequently, modifications to passenger cars and derivatives manufactured on or after 1 January 1969 will only be accepted if an engineering report prepared by a Chartered Professional Engineer is supplied.

The report must demonstrate that the modified vehicle continues to comply with all applicable Australian Design Rules, and that the vehicle meets with Fact Sheet MR810 - Torsional Stability Requirements (861.1 KB PDF).

In the case of passenger cars and derivatives manufactured prior to 1 January 1969, no approval or inspection of the modified vehicle is required. However, it is recommended that a Chartered Professional Engineer is engaged to ensure that the integrity of the vehicle has not been compromised.

Windscreens and windows

Any replacement glass fitted to a motor vehicle, including an interior partition, must be of appropriate automotive safety glass or other approved material and must comply with the Standards.

Some manufacturers incorporate the windscreen and rear window into the structural design of the vehicle and if improperly secured may reduce the crash worthiness of the vehicle.

Vehicle glazing must comply with the same characteristics as material mentioned in any of the following standards:

  • AS208, ECE R43/00, BS AU178, JIS R 3211, AN Z26.1 or NZS 5443.
  • The windscreen glass must carry the indelible mark or marks of the relevant standards. These must be visible when the windscreen is fitted in the vehicle, and the marking must identify the type of glass and the relevant standard to which the glass conforms.
  • All replacement transparent material must be of a type that will not shatter.
  • The windscreen must be free from scratches, cracks or chips.

Window tinting

Surface films reduce light transmission through windscreens and windows. This can significantly reduce a driver's vision, particularly at night and during periods of low visibility.

The windscreen of a motor vehicle must have a luminous transmittance of at least:

  • 75% for a motor vehicle built after 1971
  • 70% for any other motor vehicle.

The windscreen of a vehicle cannot be fitted with a film that reduces visible light transmittance except for the area above the highest point swept by the windscreen wipers or the upper 10% of the windscreen.

If the windows of a motor vehicle are coated to reduce light transmittance, the following requirements apply:

  • visible light transmittance must not be less than 35% when measured through glass and the film together
  • reflectance in the visible light range must not exceed 10%.

For more information please read the Fact Sheet MR430 - Window Tinting on Vehicles (72.4 KB PDF).

Bonnet pins and mascots

The use of bonnet pins that protrude through the bonnet is not acceptable.

Bonnet pins that were original equipment from the manufacturer may be acceptable. Bonnet securing devices that are flush with the contours of the bonnet may be used.

Mascots are acceptable if they were provided as original equipment by the manufacturer for a particular make and model of vehicle.

Bonnet scoops

Fitting a bonnet scoop (forward or rearward facing) to a motor vehicle is only acceptable provided that it is designed, built and fitted in a way that minimises the likelihood of injury to a person accidentally making contact with the vehicle.

For more information please read the Fact Sheet MR804 - Bonnet Scoops (268.4 KB PDF).

Hazardous projections

An object fitted to a vehicle must be designed, built and fitted to the vehicle in a way that minimises the likelihood of injury to a person making contact with the vehicle.

However, if the vehicle was designed before 1965 and such object was part of the design of the vehicle this may be permissible.

All equipment inside the vehicle such as fire extinguishers, GPS navigation or additional gauges should be securely fastened.

It is recommended that cargo anchorage systems should be capable of withstanding a force equal to twenty times the mass of the equipment.

Cargo barrier protection screens are available for many station wagon and light commercial vehicles and are highly recommended.

No vehicle may be equipped with:

  • any object or fitting not technically essential to the vehicle eg fishing rod holders.
  • any object or fitting technically essential to such vehicle unless its design, construction and conditions and the manner in which it is affixed to the vehicle reduces to a minimum the risk of bodily injury to any person
  • any object or fitting which, because it is pointed or has a sharp edge, is likely to increase the risk of bodily injury to any person
  • any bumper bar, the end of which is not turned towards the body of the vehicle to a sufficient extent to avoid any risk of hooking or grazing.

For more information please read the Fact Sheet MR800 - Hazardous Projections (1.3 MB PDF).

Roll cages

Due to the increased risk of occupant injury in vehicle accidents, fitting full roll cages is not permitted. However, fitting a half roll cage rearward of the driver may be acceptable providing that:

  • no part of the roll cage can be contacted by vehicle occupants when positioned in their normal seating position
  • the roll cage is at least 150 millimetres behind the front seat occupants when the front seats are located in the most rearward adjusted position
  • all rear seats and seat belt assemblies fitted in the rear compartment are removed
  • the operation and effectiveness of the front seat belt assemblies is not affected in any way by the roll cage
  • no person travels in the rear of the vehicle at any time
  • the vehicle has a seating inspection carried out by the Department for Infrastructure and Transport.

Bull bars

Bull bars must be designed and fitted so that the safety of the vehicle is not affected and not be of danger to other road users including pedestrians.

Bull bars must be fitted correctly and be free of sharp protrusions. They must not obscure the driver's view or any vehicle lights including indicators.

Fitting fishing rod holders to the front of a bull bar is not acceptable.

Vehicles fitted with an airbag or manufactured to comply with Australian Design Rule 69 - Offset Frontal Impact Occupant Protection or both ADR 69 and ADR 73 - Offset Frontal Impact Protection, may only be fitted with a bull bar that has been certified by the vehicle manufacturer as suitable for the vehicle, or has been demonstrated by the bull bar manufacturer to comply with ADRs 69 and 73.

Tilt fronts

'Tilt front' is a term used to describe a type of forward pivoting integral engine bonnet, grille and front mudguard assembly for front engine vehicles.

Examples of production vehicles fitted with this type of engine access are the Jaguar 'E' type and the Chevrolet Corvette.

The fitting of a tilt front is only acceptable if:

  • The new body sections are designed and constructed with no dangerous or sharp projections so that in the event of an accident the risk of injury to pedestrians and cyclists is minimised.
  • The new body sections do not obstruct the visibility of lamps fitted to the front of the vehicle, particularly the direction turn signal lamps (indicators) or headlamps.
  • The new body sections do not obstruct the field of view of the driver.
  • The field of view requirements are determined as follows:
    • with the driver's seat in the rearmost position, it is possible to see, unobstructed for the full width of the vehicle, a line drawn on the roadway 11 metres ahead of the driver's eye position when looking over the bonnet
    • for the purpose of this requirement the driver's eye position shall lie at the bottom of the 95th percentile eye ellipse (reference Australian Design Rule (ADR) 15/01 clause
    • alternatively, the driver's eye position can be taken as a point 750 millimetres above and 270 millimetres forward of the junction of the seat cushion and seat squab with the seat in the lowest and rearmost position
    • all lights fitted to meet the requirements of Road Traffic (Light Vehicle Standards) Rules 2018 and where applicable Australian Design Rule 6/00 the anchoring, hinge and latching mechanisms are durable and have sufficient strength to secure the hinged section.

The Department for Infrastructure and Transport may request a submission from a Chartered Professional Engineer if doubt exists concerning the strength of components.

In the case of passenger cars and derivatives manufactured on or after 1 January 1969, in addition to the above, an engineering report presented by a Chartered Professional Engineer demonstrating that the vehicle continues to comply with Australian Design Rule requirements, may be required.

Mudguards and mudflaps

Mudguards must be fitted to all road wheels and must cover the full width of the tyre when viewed from directly above.

They must prevent direct contact with the upper half of the wheel in forward collisions and be designed to reduce the dangers to road users from contact with moving wheels.

They must deflect downwards any stones, mud, water or other material thrown upwards by the rotation of the wheels.

For vehicles manufactured on or after 1 July 1988, specific requirements relating to the design and construction are contained in Australian Design Rule 42.

The wheel guard including the mudflap (if fitted) must be no higher than 230 mm from the ground and for off-road vehicles no higher than 300 mm from the ground. For more information on this requirement see the Road Traffic (Light Vehicle Standards) Rules 2018.

Contact DIT Vehicle Standards

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Page last updated 17 December 2021

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