Chain of Responsibility for Traffic Control Companies Running Heavy Vehicles

If your traffic control company runs truck-mounted attenuators, sign trucks or other vehicles over 4.5 tonnes GVM, it is a party in the chain of responsibility under the Heavy Vehicle National Law. Chain of responsibility for traffic control means a primary duty to ensure, so far as reasonably practicable, the safety of your transport activities, plus a due diligence duty for executives.

Many TC operators think of chain of responsibility (CoR) as a freight industry issue. But a company that schedules a TMA operator for a night shift, loads a truck with barriers and signs, and sends it to a job across town is performing several CoR functions every day. This guide explains what that means in practice.

This is general information, not legal advice. Check current requirements with the National Heavy Vehicle Regulator and get advice for your business.

Does CoR apply to your fleet?

The HVNL applies in participating jurisdictions, which is every state and territory except Western Australia and the Northern Territory. WA has chain of responsibility provisions in its own road traffic legislation, covering matters such as mass, dimension and loading, and the NT has its own heavy vehicle laws. Vehicles from those places must comply with the HVNL when they cross into participating states.

Under the HVNL, a heavy vehicle is generally a vehicle with a GVM or ATM over 4.5 tonnes, or a combination that includes one.

Check the actual plates on your vehicles rather than relying on assumptions. The same ute can be under the threshold empty and different when hitched to a heavier trailer.

The functions you perform

The HVNL identifies ten functions in the supply chain: employer of a driver, prime contractor of a driver, operator of the vehicle, scheduler of goods or passengers, consignor, consignee, packer, loading manager, loader and unloader. Duties attach to the function performed, not the job title.

A typical TC company performs several of these:

• Employer of TMA operators and truck drivers.
• Operator of the TMA and equipment trucks.
• Scheduler, when rostering and dispatch decide when and where drivers go.
• Loader and loading manager, when the depot loads signs, stands, cones and barriers.
• Consignor, when you send equipment to a client's site on someone else's truck.

Your clients may also be CoR parties, for example a principal contractor that sets impossible start times or asks your TMA to arrive at a site across the city straight after a long shift elsewhere.

The primary duty and executive due diligence

Each party must ensure, so far as reasonably practicable, the safety of its transport activities. That covers eliminating or minimising risks to drivers, other road users and the public, and making sure your conduct does not cause or encourage breaches such as speeding, fatigue or overloading.

Executives of the business have a personal due diligence duty. NHVR guidance describes it as taking reasonable steps to:

• keep up-to-date knowledge of safe transport activities;
• understand the business's transport activities and their hazards and risks;
• make sure the business has and uses suitable resources and processes to manage those risks;
• make sure the business has processes to receive and respond to information about hazards and incidents;
• make sure the business has processes to comply with its duties; and
• verify that those resources and processes are being provided and used.

The last point is where many businesses fall short. A policy in the manual is not verification. A monthly review of actual hours, defect reports, load checks and incidents is.

Rosters, speed and fatigue

Rostering is a transport activity. A schedule that sends a TMA operator to a 10 pm start 90 minutes from the depot, after a day of other work, creates risk before the vehicle moves.

Key points for TC rosters:

• Total work, not just shift time. Count travel, depot time, pre-starts and the drive home.
• Realistic start times. If the only way to make a start time is to speed, the schedule causes speeding.
• Fatigue-regulated vehicles. Work and rest hours and work diaries apply to fatigue-regulated heavy vehicles. The HVNL amendments that commenced on 1 August 2026 changed parts of the fatigue and record-keeping framework, so check with the NHVR how the current rules apply to your fleet.
• Unfit to drive. From 1 August 2026, the amended HVNL includes an unfit-to-drive duty that NHVR says applies to all drivers of heavy vehicles over 4.5 tonnes. It covers illness, injury, stress and mental illness as well as fatigue. CoR parties must make sure their business practices do not cause or encourage unfit driving and take reasonable steps to confirm drivers are fit before they drive.

Traffic control companies set their own fatigue limits from a risk assessment. TrafWise's defaults, for example, are 12 hours per day, 50 hours per week and 10 hours' rest between shifts, which are company settings rather than law. Test rosters with the roster fatigue checker, and see our guides to fatigue management for traffic controllers and traffic controller rostering.

Loading, load restraint and mass

TC loads are awkward: sign stands, signs, cones, sandbags, barriers, lighting and arrow boards, often loaded quickly at the start of a shift and unloaded at the end.

Common risks:

• Unrestrained cones and signs that can fall from the tray onto the road.
• Stands and frames stacked loosely, shifting under braking.
• Water-filled barriers that are far heavier when filled; make sure they are emptied before transport unless the vehicle and restraint are designed for them.
• Sandbags and weights that add up to more mass than expected.
• Equipment above cab height or extending beyond the vehicle.

The NHVR publishes a Load Restraint Guide covering performance standards and restraint methods. Use cages, racks and restraint points designed for the load, and include load checks in the vehicle pre-start. Our traffic control ute set-up guide covers loading for lighter vehicles.

Vehicle standards, modifications and maintenance

TMA trucks and equipment trucks are often modified: attenuator mounts, arrow boards, cranes, racks and lighting. Modifications to heavy vehicles may need approval or certification under the heavy vehicle standards, so check with the NHVR or a certifier before fitting new equipment. Attenuators must be inspected and certified as the manufacturer and the relevant guideline require, and after any impact; see our truck-mounted attenuator guide.

Maintenance systems should include:

• daily pre-start checks by the driver;
• a defect reporting process that leads to repair before use;
• scheduled servicing records; and
• checks after any incident, however minor.

Hired-in TMAs, subcontractors and client pressure

Many TC companies hire TMAs and operators from specialist providers or subcontract whole crews. That does not remove your CoR duties if you are scheduling the work or directing start times. Each party in the arrangement has its own duty, and duties can overlap.

Practical steps:

• Ask the provider about their system. How do they manage fatigue, maintenance, attenuator certification and driver fitness? Keep the answer on file.
• Share the real schedule. Tell the provider about travel distance, start times and expected finish, including likely overruns.
• Do not push a provider's driver past their limits. If a job extends, agree relief rather than asking the operator to "just finish the night".
• Push back on unreasonable client demands. A client who insists the TMA arrive at a second site immediately after a long shift elsewhere is creating risk. Record the conversation and the outcome.

Contract clauses can allocate responsibilities and require information, but they cannot transfer the duty itself. A clause saying the subcontractor is responsible for fatigue does not help if your dispatch decisions caused the fatigue.

After a TMA impact

If a TMA is struck, help people and make the site safe first. A notifiable incident must be reported to the WHS regulator and the site preserved except to help people or make it safe. Then check the driver's fitness before they drive again, and keep the vehicle and attenuator out of service until inspected and certified.

CoR controls and the evidence that proves them

Keep records that reflect what actually happened, not just the plan. A roster that says ten hours and a docket that says fourteen tells its own story.

Next steps

Map your fleet against the 4.5 tonne threshold, identify the CoR functions you perform and check the current requirements with the NHVR, along with the WHS duties explained by Safe Work Australia. TrafWise can help by keeping rosters, actual hours, fatigue checks and pre-starts in one place, so the evidence of your controls is there when you need it.