Key takeaways
- End-of-queue management means predicting how far the queue will reach, warning drivers before they meet its tail, and monitoring and adjusting through the shift.
- The back of the queue is often well upstream of the work and out of sight of the crew, so it needs its own plan, not just the advance signs.
- In NSW, TS 05492 added end-of-queue management requirements; Queensland and Western Australia have also strengthened their guidance, so check current documents.
- Queue length depends on arrivals, stop time and space per vehicle, and a queue that does not fully clear each cycle will keep growing.
- Set measurable triggers with named actions, such as moving warning devices, shortening stops or releasing the queue, before the shift starts.
End-of-queue management at roadworks means predicting how far the queue will reach, warning approaching drivers before they meet the back of it, and monitoring and adjusting through the shift as it grows. The aim is to stop fast-moving traffic running into stationary vehicles, one of the most serious crash risks at roadworks, particularly on high-speed roads.
Most traffic plans put a lot of effort into the work area: tapers, buffers, delineation and the stop position. The back of the queue gets less attention, partly because it moves and partly because it is often hundreds of metres away from anyone on the crew. This guide covers why the queue tail is dangerous, what has changed in state requirements, how to estimate queue length, how to warn drivers, how to keep queues short, and how to set triggers so the crew knows exactly what to do when the queue outgrows the plan.
This is general information, not engineering advice. End-of-queue arrangements are designed by a suitably qualified person and shown on the TGS.
Why the back of the queue is dangerous
At the work area, drivers are warned by layers of signs and can see the activity. At the queue tail, the situation is different:
- The queue moves. It grows and shrinks with each stop cycle and with traffic demand. A queue that ended well inside the advance warning signs at 7 am can extend beyond them at 8 am.
- Drivers do not expect it. On a high-speed rural road or a motorway, a driver coming over a crest or around a bend may find stationary traffic with no warning that makes sense to them.
- It is out of sight. The crew and the stop/slow controller usually cannot see the tail. Nobody notices it has moved until something happens.
- The people at risk are road users. The occupants of the last vehicles in the queue are the most exposed, along with anyone working near the tail.
- Heavy vehicles need more room. A loaded truck needs much more distance to stop than a car.
Stopping distance rises steeply with speed, so the faster the approach, the further upstream the warning has to start.
What has changed in state requirements
Requirements have been tightening across Australia.
- NSW. On 25 June 2026, Transport for NSW replaced the TCAWS Technical Manual Issue 6.1 with TS 05492:1.0 Traffic Control at Work Sites. The new standard added requirements on end-of-queue management, along with crash attenuators and temporary speed zoning. Some supporting checklists and templates were still being developed. Our guide to what changed from TCAWS to TS 05492 covers the wider changes. Check current requirements with Transport for NSW and confirm which document your project specifies.
- Queensland. Transport and Main Roads has amended its guideline on traffic management at works on roads to recommend that end-of-queue risk control measures be considered and implemented at any site.
- Western Australia. Main Roads WA guidance requires an end-of-queue calculation whenever shuttle flow is used, with queue lengths monitored on site and adjusted as required.
The national Austroads Guide to Temporary Traffic Management provides the framework that states adopt with their own supplements. The direction is clear: end-of-queue risk is expected to be planned, not left to chance.
Predicting how far the queue will reach
The basic idea is simple. Queue length depends on:
- How many vehicles arrive while traffic is stopped, which depends on traffic volume at the time of work.
- How long traffic is stopped, set by the stop/slow cycle, portable signal timing or the work method.
- How much road each vehicle takes, including the gap to the vehicle in front. Trucks and buses take far more space than cars.
- Whether the queue clears during the go phase.
A simple illustration, with assumed values: if 600 vehicles an hour approach in one direction, that is 10 vehicles a minute. Stop them for 3 minutes and around 30 vehicles queue. If you allow about 8 metres of road per vehicle including the gap, purely for illustration, the queue is roughly 240 metres long. Add heavy vehicles and it grows quickly. Your road authority's method and the designer set the actual values.
The fourth factor is the one that catches people out. If more vehicles arrive than can get through during each go phase, the queue does not fully clear, and the next stop starts with vehicles already waiting. The queue grows cycle after cycle. Peak periods, school traffic and event traffic are typical triggers.
Our free queue length and delay estimator helps you test scenarios, including how longer stop times change the queue. Treat it as a planning aid. The TGS designer decides the design values.
Warning drivers before the queue
Warning devices need to sit upstream of the longest queue the plan expects, with enough distance for drivers to slow and stop. The designer sets the positions. Typical tools include:
- Queued traffic signs. Road authorities publish signs for queued traffic. Transport for NSW, for example, has Queued Traffic and Queued Traffic Prepare to Stop signs, including a version with flashing lights.
- VMS boards upstream with short queue messages, placed beyond the expected queue so drivers get the message in time.
- Movable warnings. Some TGSs allow warning devices to be moved upstream as the queue grows, within set limits. That needs a safe method, a named person and a vehicle, not someone walking along a high-speed shoulder.
- A queue warning or protection vehicle. On some high-speed jobs the plan specifies a vehicle with flashing lights, an arrow board or a VMS, sometimes an attenuator vehicle, positioned upstream of the tail. Our guide to truck mounted attenuators covers TMA operation.
- Queue detection technology. Some projects use sensors that detect slow or stopped traffic and change upstream VMS messages automatically.
Keeping queues short in the first place
The best end-of-queue control is a short queue. Options to discuss with the client and designer include:
- Work outside peak periods, within the road occupancy or permit hours.
- Shorter stop times, by shortening the work area or the shuttle length.
- Better signal timing where portable signals are used.
- Detours or pre-warnings that encourage some traffic to use other routes.
- Releasing the queue when it reaches a set length, even if that pauses the work.
- Staging the work so the most disruptive tasks happen at the quietest times.
Our guide to stop/slow traffic control covers cycle management at the stop position.
Monitoring and trigger points
A queue estimate is a prediction. The site needs to check it and act when reality is different. Set triggers before the shift, with named actions and a named person.
| Trigger | Example | Typical action (as the TGS and briefing allow) |
|---|---|---|
| Queue reaches a set marker | Tail passes a marked sign or landmark | Shorten stop times; alert the supervisor |
| Queue nears the first advance warning | Tail within a set distance of the first warning device | Move or add warnings as the plan allows; release the queue |
| Queue reaches a crest, bend or intersection | Tail out of sight of approaching drivers | Release the queue; pause the work |
| Queue nears a rail level crossing | Vehicles could stop on or near the tracks | Release the queue immediately; follow the rail interface plan |
| Queue does not clear in one go phase | Vehicles still waiting when the next stop starts | Adjust the cycle; escalate for review |
| Incident in the queue | Crash, breakdown or medical emergency | Emergency procedure; protect the scene; call emergency services |
Queues near railway crossings are a special case. See our guide to roadworks near rail level crossings.
Monitoring methods include a spotter in a vehicle parked in a safe position, regular drive-throughs, radio reports from controllers, traffic apps and, on larger projects, CCTV or detection systems. Record each observation with time, direction and how it was measured. Our guide to roadworks queue monitoring covers recording and escalation.
Briefing the crew on end-of-queue arrangements
At the pre-start, cover:
- the predicted queue length and where the tail is expected at peak
- the markers or landmarks used as triggers
- who monitors the queue and how often they report
- the radio channel and calls for queue reports
- who is authorised to release the queue or pause work
- the safe method for moving warning devices, if the TGS allows it
- emergency procedures for an incident in the queue
End-of-queue checklist
| Check | Done |
|---|---|
| Queue estimate done for the hours of work | ☐ |
| Warning devices placed beyond the predicted queue | ☐ |
| Trigger markers identified and briefed | ☐ |
| Queue monitor named, with reporting interval | ☐ |
| Authority to release the queue or pause work confirmed | ☐ |
| Rail crossings, crests and intersections on the approach identified | ☐ |
| Queue observations recorded with time and direction | ☐ |
| Triggers and actions taken recorded | ☐ |
| Repeated exceedances escalated for TGS review | ☐ |
Next steps
Add queue triggers to your next pre-start and test your cycle times with the queue estimator before the job. If you run a traffic control company, TrafWise records briefings, inspections and site notes on digital dockets, so queue observations and actions are kept with the job.
Frequently asked questions
What is end-of-queue management at roadworks?
End-of-queue management is the planning and site work that protects drivers arriving at the back of a queue caused by roadworks. It includes predicting queue length, placing warnings before the queue tail, monitoring the queue during the shift, and acting when it grows beyond the plan, for example by moving warnings, shortening stops or releasing traffic.
Why are end-of-queue crashes so dangerous?
Drivers approaching at highway speed may not expect stationary traffic, especially over a crest or around a bend, so they can run into the back of the queue with little or no braking. The stopped vehicles are often far from the work area and the crew, so nobody on site sees the problem developing until it is too late.
How do you estimate queue length at roadworks?
Estimate how many vehicles arrive during the time traffic is stopped, then multiply by the road space each vehicle takes, including the gap. Heavy vehicles take much more space. Use peak volumes for the hours of work. Your road authority's method and the TGS designer set the values, and the estimate should be checked on site.
What signs warn drivers of queued traffic at roadworks?
Road authorities publish queued traffic warning signs, and Transport for NSW has signs such as Queued Traffic and Queued Traffic Prepare to Stop, including a version with flashing lights. VMS boards upstream can also warn of queues. Which signs are used, and where, is set by the TGS for the job.
What should happen when the queue grows longer than planned?
The crew should follow the triggers set in the TGS and briefing. Typical actions include moving or adding warning devices as the plan allows, shortening stop times, releasing the queue, pausing the work or opening a lane. The supervisor should record the queue length and time and escalate for a TGS review if it keeps happening.