Worked Example: A Mobile Works Convoy on a Multi-Lane Arterial

Mobile works traffic control on a multi-lane arterial means protecting moving work with vehicles instead of cones: a work vehicle, a shadow vehicle with an arrow board and usually a truck-mounted attenuator, and sometimes an advance warning vehicle, all spaced and signed as the TGS requires. The crew drives the route first, uses fixed radio calls and logs every stop.

This is an example scenario across one day shift. It is not a real job, client or incident. It is written for supervisors, TMA operators and work crews who run mobile convoys. It is not engineering advice: the traffic guidance scheme (TGS) must be prepared by a suitably qualified person, and spacing, signs and TMA requirements come from it. For whether mobile is the right method at all, see mobile vs static traffic management.

The example job

Example scenario: a road maintenance crew is sealing cracks and patching small potholes in the kerbside lane of a divided arterial.

• Road: three lanes each way, divided by a median, posted 70 km/h, signalised intersections roughly every few hundred metres, bus stops in the kerbside lane, several side streets and driveways.
• Length: about 4 kilometres of the northbound kerbside lane in one shift.
• Work: the work vehicle stops at each defect for a few minutes while two workers seal or patch from the kerb side, then moves on.
• Hours: 9:30 am to 3 pm, between peaks, as the permit allows.
• Convoy (per the TGS): the work vehicle at the front, a shadow vehicle with an arrow board and TMA behind it, and an advance warning vehicle with signs further back.
• Crew: the supervisor (driving the advance warning vehicle), the TMA operator, the work vehicle driver and two workers.

The day before: driving the route

The supervisor drives the full length in the kerbside lane at the time of day the work will happen, with the TGS on the passenger seat, and marks the hard spots.

The last row matters. Mobile works suit short stops. A repair that keeps workers out on the road for an extended period needs the static lane closure layout the TGS provides, with its own signs and taper. Knowing that before the day stops the crew from treating a long job as a quick one.

Morning pre-start: vehicles, TMA and radio calls

At 8:30 am the crew meets at the depot. The pre-start covers:

• the route, the hard spots and the static closure location
• convoy order and spacing from the TGS, and the rule that vehicles never close up to stop cars cutting in
• each person's role and who calls stops, starts and lane changes
• where workers get in and out of the work vehicle (kerb side only)
• the radio channel and backup, with a radio check from each vehicle
• the response to a TMA impact: stop, protect, check on workers, call it in, do not move the TMA until assessed
• SWMS sign-on

Vehicle pre-starts. Each driver checks their vehicle. The TMA operator checks the attenuator: deployed and stowed positions, lights, the arrow board, mounting and any signs of damage, against the manufacturer's checklist. A TMA that has been hit must be inspected before it is used again. Our guide to truck-mounted attenuators covers inspection and certification. The TMA operator holds the right heavy-vehicle licence and traffic control training.

Arrow board check. The arrow board is set to the correct display for a kerbside lane closure, pointing traffic to the right. Arrow boards set to the wrong arrow are a common mistake. See arrow boards for road works.

The radio calls

Mobile convoys live and die on short, consistent calls. The briefed set for this job:

The shift: what happens and the fixes

9:35 am. First stop. "Stopping, defect ahead." The work vehicle pulls up at the crack, the TMA stops behind it at the spacing in the TGS, and the advance warning vehicle stops further back. "Workers out." The workers seal from the kerb side. Four minutes later, "Workers in. Convoy moving."

9:50 am. A cut-in. A white van overtakes the advance warning vehicle, swings left between the TMA and the work vehicle while the convoy is stopped, then stops behind the work vehicle to turn into a driveway. The workers are back in the vehicle. The TMA operator calls "Cut-in, white van". Nobody closes up or sounds a horn. The van turns out and the work resumes. The supervisor logs the time and vehicle. If cut-ins keep happening at the same kind of spot, that is a reason to review the spacing or signs with the designer, not to close the gaps.

10:20 am. Intersection 1. The kerbside lane becomes a left-turn lane. "Merging right at intersection." All three vehicles signal and move right in order, the advance warning vehicle first, then the TMA, then the work vehicle, so the convoy shape stays intact. After the intersection, they move back in the same order.

11:05 am. Bus stop A. "Bus behind." A bus wants the stop just ahead. The supervisor calls the convoy past the stop without stopping, the bus pulls in behind, and the crew patches the defect at the stop on the way back later when no bus is due.

12:00 pm. Break. The convoy pulls off the arterial into a side street away from traffic for the lunch break. The TMA operator gets out of the cab and walks around, because sitting in a stationary TMA for long periods is tiring.

1:15 pm. The big pothole. "Going static." The convoy stops before the overpass in the protected position. The supervisor and workers set up the static kerbside lane closure from the TGS, in order, with the TMA positioned as the static layout shows. Once the repair is done, the static layout is removed in reverse and the crew resumes mobile works.

2:10 pm. A near miss. A car brakes heavily and stops just short of the TMA after its driver, apparently on a phone, looks up late. The TMA operator records the time, location and vehicle. That is exactly the situation the TMA is there for.

Leaving the road at the end of the shift

Ending a mobile shift is a manoeuvre in its own right, and crews often treat it as the drive home. In the example, the end point is a wide side street where the convoy can leave the arterial without stopping in a live lane.

1. "Last defect done, workers in." The work vehicle confirms the workers are seated and the doors are shut.
2. The supervisor calls the exit: the convoy signals and turns into the side street in order, work vehicle first, TMA second, advance warning vehicle last, so protection stays behind the work until the end.
3. Once all three are off the arterial and parked clear of traffic, the arrow board is switched off and the TMA stowed.
4. Signs on the advance warning vehicle are covered or folded so drivers on the way back to the depot do not see a work message with no work.
5. The supervisor walks around each vehicle for damage, especially the TMA, and notes anything for the depot.

The finish location and time go in the record, along with materials used, which helps the next crew pick up where this one stopped.

Common convoy mistakes and how to catch them

What gets recorded

For current guidance, check Austroads for the AGTTM and Transport for NSW for NSW requirements under TS 05492. For heavy-vehicle licensing and duties, see the National Heavy Vehicle Regulator. Similar convoys support line-marking traffic management.

Next steps

Before your next mobile works shift, drive the route and mark the hard spots, brief a fixed set of radio calls and agree the trigger for going static. Operators can keep TMA inspections and rego renewals on an equipment register with reminders in TrafWise.