Worked Example: Short-Duration Shoulder Works on a 100 km/h Highway

Highway shoulder works at 100 km/h need a deliberate, approved arrangement even when the job takes an hour: advance signs, a protected work area, usually a vehicle or truck-mounted attenuator (TMA) behind the crew, and a fixed set-up and pack-down order. Whether the adjacent lane closes too depends on how close the work gets to traffic.

This article walks through one example job step by step. It is a teaching scenario, not a real project. Distances, devices and vehicle positions come from the approved traffic guidance scheme (TGS), which must be prepared by a suitably qualified person using AS 1742.3, the Austroads Guide to Temporary Traffic Management (AGTTM) and the state supplement. This is general information, not legal or engineering advice. For the layout options, see our guide to shoulder closures and short-term works.

The example job

Example scenario: a maintenance contractor has to replace a damaged roadside sign and two guide posts on the left shoulder of a divided highway with two lanes in each direction, signed at 100 km/h. The shoulder is sealed and reasonably wide; beyond it is a grassed verge and a drainage swale. Traffic is heavy with a high share of trucks. The work involves digging out the old sign footing, installing a new post and sign, and replacing the guide posts. On foot, it should take about two hours.

The crew is a traffic supervisor and a TMA operator from the traffic control company, and two maintenance workers with a crew truck. The road authority has approved a short-duration shoulder closure for a weekday off-peak window, with the TGS supplied by the contractor's designer.

The decisions behind the TGS

The designer works through a series of questions before choosing the arrangement. The answers come from site information, traffic data and the standards, not from a rule of thumb.

In this example, the designer's TGS closes the shoulder only, with the left lane kept open, but with a condition that if workers or plant need to enter the area close to the lane, the supervisor stops that activity until a lane closure under a second TGS is in place. That condition is the important part. Our article on short-term low-impact traffic management explains why the actual limits matter more than the label.

Why 100 km/h is unforgiving: an example calculation

The figures below are an illustrative physics calculation, not design values. Assume a 2-second perception and reaction time and steady braking at 4.4 m/s², a moderate value chosen for illustration.

• At 100 km/h (27.8 m/s): reaction distance is 27.8 × 2 = about 56 metres; braking distance is 27.8² ÷ (2 × 4.4) = about 88 metres; total about 144 metres.
• At 80 km/h (22.2 m/s): about 44 metres plus 56 metres, total about 100 metres.

A vehicle drifting onto the shoulder at highway speed reaches the work area in seconds. That is why the TGS uses a TMA, a buffer and early warning, and why the crew does not rely on drivers seeing them. Try the numbers with our free stopping distance calculator. For more on what protects crews from errant vehicles, read what is a truck-mounted attenuator.

Set-up order: the most exposed part of the job

Set-up is done in a fixed order, working with the traffic, always from the protection of a vehicle where the TGS and the procedure provide it.

1. Pre-start and SWMS sign-on at a safe location off the highway. Work on or next to a road used by traffic is high-risk construction work, so a SWMS is required. The TMA operator checks the TMA and its inspection status.
2. Briefing: the TGS, the condition about the lane edge, the escape direction, the lookout, the entry and exit procedure and radio calls.
3. Advance signs placed in order from the furthest upstream, by the crew working from the vehicle and on the shoulder, facing traffic where they can.
4. Speed signs and covers on conflicting permanent signs, as approved.
5. Shoulder closure with delineation per the TGS.
6. TMA positioned behind the work area at the location the TGS shows, with its arrow or warning display on.
7. Crew truck enters the work area behind the TMA.
8. Supervisor checks the set-up against the TGS and records it with photos taken from a safe position.

Radio call when set-up is complete: "Set-up complete, TMA in position, work area clear to start." No digging starts until that call.

Running the job: exposure, lookouts and what goes wrong

During the work, the supervisor acts as lookout, facing traffic, with an agreed warning signal (an air horn, for example) and the escape direction briefed. Workers keep tools and materials inside the closed area and away from the lane edge, and nobody steps towards the lane to retrieve anything that blows out.

What goes wrong in this example, and the fix:

• The old footing is bigger than expected and needs the excavator closer to the edge line. Under the TGS condition, the supervisor stops that activity. The contractor decides whether to install the lane closure under the second TGS or come back in another window. Nobody improvises a lane closure on a 100 km/h road.
• A truck drifts across the edge line past the TMA. The lookout sounds the warning, the crew moves to the escape side, and nobody is struck. The supervisor records the time and vehicle details, checks the signs and TMA position, and reports it. Our guide to work zone intrusions covers investigation and prevention.
• Wind blows an advance sign over. The supervisor arranges for it to be reset from the protection of a vehicle, not by someone walking back along the shoulder against traffic.
• The window is running out. Pack-down must finish inside the approved window, so the supervisor calls the stop in time to pack down, even if the guide posts are not finished.

Common mistakes on high-speed shoulder jobs

• Calling it "just a quick job". Short duration changes which arrangement may be allowed; it does not change the speed of the traffic. The approved TGS still applies in full.
• Parking the crew truck in front of the TMA. The TMA protects what is behind it. A crew truck parked upstream of it, or beside it in the shoulder, is unprotected and blocks drivers' view of the warning display.
• Walking back along the shoulder. Fetching a forgotten tool or resetting a sign on foot, with your back to traffic, is one of the most exposed things a worker can do. Use the vehicle.
• No lookout. When everyone is head-down digging, nobody sees the drifting truck. Give one person the job and nothing else.
• Stretching the TGS. Moving plant closer to the lane "for a minute" breaks the condition the designer relied on. Stop the activity, then decide.
• Leaving signs out after the window. Advance and speed signs left on the highway after the work area is gone teach drivers to ignore roadwork signs. Check every device is collected.
• Rushing the merge. Accelerating from the shoulder into 100 km/h traffic needs a long gap. Drivers of the crew truck and TMA should wait for one, not force it.

Pack-down order and leaving the site

Pack-down is the reverse of set-up, and it is just as exposed.

1. Work area cleared: tools, spoil, old sign and posts loaded; surface checked for debris.
2. Crew truck leaves the work area, merging from the shoulder when safe, as the TGS shows.
3. Shoulder closure devices collected from downstream to upstream, working from the vehicle with the TMA protecting where the procedure requires.
4. Speed signs and covers removed, permanent signs uncovered.
5. Advance signs collected last.
6. Supervisor drives the section to confirm nothing is left behind.

The shift record

In NSW, Transport for NSW's TS 05492 Traffic Control at Work Sites replaced the TCAWS manual on 25 June 2026 and adds requirements on crash attenuators and temporary speed zoning, so check the version your project uses with Transport for NSW. Queensland projects work under the state's own manuals; start with Transport and Main Roads. The national guide is at Austroads.

Next steps

Before your next high-speed shoulder job, check the TGS for the conditions that would force a lane closure, and brief the crew on exactly what to stop if those conditions arise. If you run traffic control crews, TrafWise tracks TMA inspections and registration in the equipment register and records pre-starts and SWMS sign-ons for every shift.