Key takeaways
- The clear zone is the area beside the traffic lane that should be free of hazards, so a vehicle that leaves the road can stop or recover safely.
- Its width depends on speed, traffic volume, curvature and roadside slopes, and is wider on the outside of curves and on fast, busy roads.
- Roadworks fill the clear zone with plant, stockpiles, excavations, drop-offs, stored devices and barrier ends, and the risk peaks overnight when nobody is there.
- Treat hazards in order: remove, relocate, make traversable, make frangible, shield with an approved barrier, and only then delineate.
- An end-of-shift walk of the clear zone, recorded with photos, is one of the most valuable checks a supervisor makes.
The clear zone at roadworks is the area beside the traffic lane that should be kept free of hazards so a vehicle that leaves the road can stop or recover without hitting something solid or rolling over. Plant, stockpiles, excavations, drop-offs and barrier ends left overnight are the usual problems. Remove, relocate, make safe or shield them.
Run-off-road crashes do not stop because the crew has gone home. If anything, the risk grows at night: drivers are tired, the site is dark and nobody is there to notice that a stockpile has spread or a sign has blown into the lane. This guide explains the clear zone concept, the hazards roadworks create, the treatment hierarchy and the end-of-shift checks that matter. It is general information, not engineering advice. Clear zone assessments and barrier designs must be done by suitably qualified people using the current guides.
What the clear zone is
The clear zone comes from road design. Austroads' road design guidance describes it as the area adjacent to the traffic lane that should be kept free from features that would be potentially hazardous to errant vehicles. It is a compromise between giving every errant vehicle room to recover, the cost of providing that room and the chance of a vehicle reaching a hazard.
Key points:
- It is measured from the edge of the travelled lane, not from the edge of the seal or the kerb.
- It can include the shoulder, the verge and gentle slopes. Steep fill slopes that a vehicle cannot recover on do not count towards it, and a vehicle that goes over one may need recovery space beyond the bottom.
- Its width varies. It depends on speed, traffic volume, horizontal curvature, cut and fill slopes, and whether a barrier or steep cutting stops vehicles first. It is wider on the outside of curves and on fast, busy roads.
- Hazards outside it are generally lower risk, because few errant vehicles reach them.
Austroads' Guide to Road Design Part 6 sets out how clear zones are determined, and Queensland's supplement to the national temporary traffic management guide includes clear zone tables and adjustment figures for roadworks use. The designer determines the width for the site; do not apply a number from another job.
Why roadworks fill the clear zone
Permanent roads are designed, as far as practical, to keep the clear zone clear. Roadworks undo that in several ways:
- Work needs space beside the road. Plant, materials and spoil end up on the verge and shoulder.
- Traffic moves closer to hazards. When a lane is shifted or the shoulder becomes a temporary lane, roadside objects that were outside the clear zone can end up inside it. Queensland's supplement says exactly this about using the shoulder as a temporary lane, and applies its clear zone guidance when traffic is laterally shifted onto a different alignment.
- The site is temporary. Things get put down "for tonight" and stay for weeks.
- Nobody is watching overnight. A hazard that was managed while the crew was there may not be at 2 am.
Hazards commonly left overnight
| Hazard | Why it matters | Typical treatment to consider |
|---|---|---|
| Excavations, trenches and open pits | A wheel or vehicle dropping in can cause rollover or severe impact | Backfill, cover with suitably rated plates, or shield with a barrier |
| Edge drop-offs | Milled lanes, pavement edges and trench edges cause loss of control | Fill, ramp or wedge the edge where possible; warning and delineation; barrier for deep drops |
| Parked plant and trucks | Large rigid objects close to the lane | Park outside the clear zone or behind an approved barrier |
| Stockpiles of spoil or aggregate | Can launch or roll a vehicle, and spread into the lane | Locate away from traffic; keep low and contained |
| Stored materials | Pipes, pits, kerb units, steel and formwork are rigid and heavy | Store outside the clear zone or in a protected compound |
| Spare traffic devices | Barrier units, sign stands and ballast can be struck or blown into lanes | Remove from site or store well clear; secure against wind |
| Light towers, generators, VMS trailers | Rigid objects often placed close to traffic for visibility | Position as the TGS shows; shield or delineate where they must stay |
| Temporary barrier ends | A blunt end facing traffic is a hazard in itself | Approved end treatment, or position as the design allows |
| Star pickets, starter bars, formwork | Can spear or snag vehicles and people | Remove, cap or relocate as guidance requires |
| Site fencing feet, bins and sheds | Heavy bases near the road edge | Keep out of the clear zone |
The treatment hierarchy
Road safety practice treats roadside hazards in a set order, with the most effective options first. The same thinking appears in Austroads guidance, state supplements and council clear zone policies, and it lines up with the WHS hierarchy of controls.
- Remove the hazard. Take plant, materials and spare devices off site at the end of the shift.
- Relocate it outside the clear zone, or to a location where it is less likely to be hit.
- Make it traversable. Backfill the trench, cover the pit with plates rated for traffic, flatten the stockpile, ramp the edge drop-off.
- Make it frangible or less severe, so it breaks away or absorbs energy if hit.
- Shield it with an approved road safety barrier, with suitable end treatments and enough room behind the barrier for it to deflect.
- Delineate it so drivers can see it. This is the last resort, because delineation warns but does not protect.
Storing plant, materials and devices
Storage rules are where state guidance differs, so check the current documents for your job.
- The AGTTM's text on redundant devices refers to equipment being stored at least 6 m clear of traffic.
- Queensland's supplement, published by Transport and Main Roads, replaces that with a requirement to store equipment outside the clear zone, and to delineate it when it is within 9 m of the edge of a traffic lane, unless it is behind a safety barrier.
- Queensland's supplement also sets rules for star pickets, including that they must not be used within 1 m of the edge of the traffic lane where the speed limit is 80 km/h or more, must have end caps, must be installed vertically and should be delineated within 3 m of traffic, pedestrian or cyclist paths.
In NSW, check the current requirements in TS 05492:1.0 with Transport for NSW, which replaced the TCAWS manual on 25 June 2026, and the project's own specifications. National guidance is published by Austroads.
Barriers and attenuators left overnight
Where hazards are shielded overnight, the barrier system itself needs checking:
- Approved products. Use barrier systems and end treatments accepted by the road authority. Queensland, for example, publishes a list of accepted road safety barrier systems and devices.
- Installed as designed. Correct length, alignment, connections, anchoring and fill level for water-filled units, to the manufacturer's requirements.
- Ends treated. Leading ends within the clear zone need an approved terminal or crash cushion, or positioning as the design allows.
- Deflection space clear. Nothing stored, parked or excavated behind the barrier within its deflection width.
- Visible. Barrier delineation clean and reflective so drivers can see the line of the barrier at night.
The end-of-shift clear zone walk
The most useful habit a supervisor can build is walking the clear zone before leaving site, on both sides of the road, looking at it as a driver who has drifted off the lane would.
| Check | Done |
|---|---|
| All plant parked outside the clear zone or behind an approved barrier | ☐ |
| Excavations backfilled, plated or shielded | ☐ |
| Edge drop-offs treated, signed and delineated as the plan requires | ☐ |
| Stockpiles low, contained and clear of the lane edge | ☐ |
| Spare devices and materials removed or stored clear and secured | ☐ |
| Barrier ends treated, connections secure, water-filled units filled | ☐ |
| Nothing within barrier deflection space | ☐ |
| Star pickets and starter bars removed or capped | ☐ |
| Signs for overnight conditions correct; signs no longer needed covered or removed | ☐ |
| Photos taken from the driver's side, in both directions | ☐ |
| After-hours contact confirmed and recorded | ☐ |
You can print our free roadworks checklists for the crew. After the crew leaves, after-care inspections check that the site stays as it was left; our roadworks after-care checklist covers that responsibility, and the traffic control demobilisation checklist covers the final pack-down. For how vehicles end up off the road in the first place, see our guide to work zone intrusions.
Next steps
At your next end of shift, walk the clear zone on both sides before signing off, and photograph what you leave. If you run a traffic control company, TrafWise keeps inspection photos and after-care records against each job, so the overnight condition of the site is always on file.
Frequently asked questions
What is the clear zone on a road?
The clear zone is the area next to the traffic lane that should be kept free of hazards that could harm the occupants of a vehicle that runs off the road. It is measured from the edge of the travelled lane and can include the shoulder, verge and gentle slopes. Its width depends on speed, traffic, curvature and slopes.
Can you park plant in the clear zone overnight?
Generally plant should be parked outside the clear zone or behind an approved barrier with enough space for its deflection. If that is not possible, the traffic management designer should assess it and specify treatment. Some state guidance also requires stored equipment within a set distance of traffic to be delineated. Check your state's current supplement.
How wide is the clear zone at roadworks?
There is no single width. Road design and temporary traffic management guidance give clear zone widths that increase with speed and traffic volume, change with cut and fill slopes and grow on the outside of curves. The designer works it out for the site using the guide adopted for the project. Do not assume a fixed distance.
What is an edge drop-off at roadworks?
An edge drop-off is a sudden level difference at the edge of a lane or shoulder, such as a milled lane next to an unmilled one, a pavement edge beside an excavation or a trench beside the road. A wheel that drops off it can cause loss of control. Drop-offs need treatment, warning or protection, especially overnight.
Are temporary barrier ends a hazard?
Yes. The blunt end of a concrete or water-filled barrier facing traffic can be a severe hazard on its own. Barrier ends inside the clear zone usually need an approved end treatment, or must be positioned or flared away from traffic as the design allows. Barrier systems must be installed to the manufacturer's requirements.