Heavy Trailer Class (HVNL s.5)

Dog Trailer

2 Axle Groups | Turntable Steer | Licence: HC (if > 9.0t ATM)

A heavy trailer comprising two axle groups (front and rear), where the front axle group is steered via a drawbar connected to the towing rigid truck's coupling.

Jump To Section: 1. Basic & Technical Info 2. Licensing & Conditions 3. Enforcement Options 4. Images & Diagrams
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1. Basic Information & Advanced Technical Specifications

  • What is a Dog Trailer? (HVNL s.5): A trailer with two axle groups of which the front axle group is steered by connection to the towing vehicle (via a hinged A-frame drawbar attached to a front dolly/ballrace turntable). If the trailer has an axle or axle group in both the front and rear thirds of the load surface, the trailer may be considered a Dog Trailer.
  • Zero Vertical Transfer & Safety Chain Exemption (ADR 62): Supports 100% of its vertical load on its own front and rear axle groups (ATM equals GTM). Exempt from safety chains under ADR 62 provided the 50mm pin coupling has a secondary positive locking mechanism.
  • Axle Group Mass Limits: 3-Axle Dog: 25.5t GML (9.0t front + 16.5t rear) | 4-Axle Dog: 33.0t GML / 34.0t CML | 5-Axle PBS Dog: Up to 39.5t HML under PBS Level 2.

2. Licensing Requirements & The Heavy Rigid Trap

  • If a driver is driving with a Dog Trailer that has an ATM of 9 tonne or more, the driver must have a heavy combination licence. Even if the trailer is unloaded or loaded less than 9 tonne.
  • The #1 Quarry Tipper Trap (s.18(1)(a) RSA): An HR licence strictly caps trailer towing at 9.0 tonnes GVM/ATM. Even if a quarry dog trailer is completely empty, its plated ATM exceeds 9.0t—making an HR driver Unlicensed for Category!

3. Advanced Enforcement Options & Roadside Powers

  • Ringfeder Coupling & Drawbar Eye Inspection (HVNL s.526): Inspect the 50mm pin safety boss, drawbar eye bushing, A-frame hinge bushes, and turntable ballrace ring. Issue a Major Defect Notice [s.526(2)(a)] for excessive play or cracking.
  • PBS Vehicle Approval & OBM Audit (HVNL s.60 / s.96): Demand the NHVR PBS Vehicle Approval on 4-axle/5-axle dogs running at 50.5t–57.5t, check route compliance, and verify On-Board Mass (OBM) scales.

4. Reference Images, Axle Configurations & Inspection Points

4-Axle Quarry Dog Trailer

4-Axle PBS Quarry Dog

Tandem front steerable dolly group + tandem rear group coupled behind a 6x4 rigid tipper (up to 50.5t–57.5t PBS).

50mm Ringfeder Coupling & Drawbar Eye

Ringfeder & Hinged Drawbar

Check secondary locking latch, drawbar eye wear bush, and A-frame hinge pins. No safety chains required on hinged drawbars (ADR 62).

Front Dolly Ballrace Turntable

Ballrace Steering Turntable

Inspect mounting bolts and vertical play between the front axle dolly subframe and trailer chassis.