This stop/slow cycle time calculator plans a single-lane shuttle run with STOP/SLOW bats, manual devices or portable traffic signals. From the length of the closure, the speed through it and the traffic each way, it works out the clearance time, the full cycle, the capacity in each direction and how long the queue gets before each release.
A shuttle that's timed badly builds queues that grow every cycle, and long queues are where rear-end crashes happen. Ten minutes with the numbers before set-up can save an hour of angry drivers and a risky end of queue.
How it's worked out
The calculator follows one full cycle: direction A released, the section cleared, direction B released, the section cleared again.
- Clearance (all-stop) time = section length ÷ (speed ÷ 3.6) + margin. This is the time for the last released vehicle to get through before the other side moves. The margin covers start-up and the controllers confirming the section is clear.
- Cycle = 2 × (release time + clearance time).
- Cycles per hour = 3,600 ÷ cycle.
- Capacity each way = discharge rate × release time ÷ cycle. The discharge rate is how many vehicles flow through per hour while a side is released (default 1,500).
- Longest wait = cycle − release time. A driver who arrives just after their side is stopped waits that long.
- Queue at release = arrivals per hour × longest wait ÷ 3,600, in vehicles. Multiply by the queue space per vehicle (default 7 m) for metres.
- Load = arrivals ÷ capacity for each direction.
A direction is flagged when its load reaches 90%, or its queue is bigger than one release can clear (discharge rate × release time ÷ 3,600). When that happens the calculator suggests a release time that brings the busier side down to about 85% of capacity:
Release time ≈ (2 × q × c ÷ 0.85) ÷ (S − 2 × q ÷ 0.85), rounded up to the next 5 seconds, where q is the busier direction's arrivals, c the clearance time and S the discharge rate. If no release time can do it, it says so.
The discharge rate is a placeholder. It depends on the road, grades, heavy vehicles and how the controllers release traffic, so count how many vehicles get through one release period on site and put your own figure in.
A stop/slow cycle time worked example
A crew is closing one lane of a two-lane road over a 150 m section. Traffic passes the work at about 20 km/h. Counts show 450 vehicles an hour in direction A and 380 in direction B.
Start with 60-second releases and a 5-second margin:
| Item | Result |
|---|---|
| Clearance | 150 ÷ 5.56 m/s = 27 s, plus 5 s = 32 s |
| Full cycle | 2 × (60 + 32) = 184 s, about 19.6 cycles an hour |
| Capacity each way | 1,500 × 60 ÷ 184 = 489 vehicles an hour |
| Longest wait | 184 − 60 = 124 s |
| Direction A | 92% loaded, about 16 vehicles queued (109 m) at release |
| Direction B | 78% loaded, about 13 vehicles queued (92 m) |
Direction A is over the 90% line, so its queue will carry over between cycles and keep growing. The calculator suggests a release time of about 80 seconds. Try it:
- Cycle: 2 × (80 + 32) = 224 s.
- Capacity: 1,500 × 80 ÷ 224 = 536 vehicles an hour each way.
- Direction A: 84% loaded, 18 vehicles (126 m) at release. Direction B: 71%, about 15 vehicles (106 m).
Both directions now clear each cycle, but the queues are longer because everyone waits longer. That's the trade-off with every shuttle: longer releases add capacity and also add queue. If the queue would pass the PREPARE TO STOP signs or reach a crest or intersection, shorten the single-lane section or change the method. The queue length calculator helps with hour-by-hour planning, and our guide to working out stop/slow cycle times walks through the same steps by hand.
The NSW rules around a shuttle
Under Transport for NSW's TS 05492 Traffic Control at Work Sites (June 2026), several rules decide whether the shuttle is allowed and how it's run.
Which device. On TfNSW work sites, Table 44 limits STOP/SLOW bats to roads with a permanent speed of 50 km/h or less. Manually operated portable traffic control devices are allowed up to 60 km/h, and remotely controlled devices such as portable traffic signals and boom barriers at any speed. Exemptions for bats (s12.4.2.1) include incident response, a controller position in place for less than 60 minutes, traffic stopped 4 or fewer times an hour, roads under 200 vehicles a day ending at a T-junction, and controllers moving within the work zone.
How many controllers. Table 46 for two-lane roads:
| Controllers | When |
|---|---|
| None | Daily traffic under 100, speed under 70 km/h, each end visible from the other, work area under 100 m and single-lane signs in place |
| One | Daily traffic up to 500 and the Table 47 sight distance is met |
| Two | Daily traffic over 500, or the work area is over 250 m, or the sight distance isn't met |
Sight distance to oncoming traffic (Table 47, up to 100 km/h): 300 m if the work area is under 60 m, otherwise the work area length plus 250 m. For the 150 m example that's 400 m. The traffic controllers needed tool runs these checks for you.
Queue estimate. NSW s11.8.3 says queues should be estimated from reliable data and checked on site through the shift. Vehicles queued = arrivals per minute × stopping time, using 8.5 m for a light vehicle, 22 m for a heavy vehicle and 29 m for a B-double, plus 30%, rounded up to the nearest 10 m. That's more conservative than this calculator's 7 m default, so for a NSW TMP set the queue space to suit or use the NSW method.
Queensland and WA
Queensland's QGTTM Part 3 Table 5.4 caps the single-lane length by two-way traffic:
| Two-way vehicles per hour | Maximum single-lane length |
|---|---|
| Up to 300 | 800 m |
| 301–350 | 600 m |
| 351–400 | 400 m |
| 401–500 | 250 m |
| 501–600 | 150 m |
| 601–700 | 100 m |
| 701–800 | 70 m |
The worked example has 830 vehicles an hour two-way, which is past the end of the table. In Queensland that layout needs traffic engineering input. Queensland also estimates queues with a 5-minute count, 6 m per average vehicle and 20 m per heavy vehicle, with a minimum of one car plus one truck.
Main Roads WA adds a clearance time step to its queue method. At 40 km/h, a 60–250 m shuttle takes 1 minute to clear and 400–800 m takes 2 minutes. Victorian values aren't loaded yet, so use your approved TGS.
On site and when to get advice
Plans are a starting point. On site:
- count how many vehicles get through one release and correct the discharge rate
- watch the real queue each cycle and adjust the release time
- never release the other side until the last vehicle is confirmed clear
- mark the predicted end of the queue so controllers can see when it's growing
For portable traffic signals, TS 05492 Appendix A sets initial all-red and green times by the distance between stop lines and says to watch three cycles and then adjust. The portable traffic signal timing tool covers that. Get the traffic management designer involved when traffic is near capacity, the queue reaches a crest, bend or intersection, or the shuttle runs through a peak. Our guides to stop/slow traffic control and portable traffic lights versus bats go further.