This km/h to m/s converter turns a vehicle's speed into the metres it covers every second. It then shows how far that vehicle travels while a driver looks away from the road, and how long it takes to reach your work area from any distance upstream.
Those three numbers are the simplest way to explain why road work layouts look the way they do. Signs sit a long way back, controllers stand where they can be seen early, and workers keep an escape route, because vehicles cover ground far faster than most people picture.
How it's worked out
Everything comes from one conversion. A kilometre is 1,000 metres and an hour is 3,600 seconds, so:
- Metres per second = km/h ÷ 3.6
- Distance in t seconds = (km/h ÷ 3.6) × t
- Time to cover a distance = distance ÷ (km/h ÷ 3.6)
The converter shows:
- the speed in metres per second
- the distance travelled during the look-away time you enter
- the time to cover your distance to the work area
- the distance covered in 1 second and in 3 seconds
- a table at 40, 60, 80, 100 and 110 km/h showing metres per second, the distance in 2 seconds and the time to cover your distance
Nothing is rounded until it's displayed. Metres per second are shown to one decimal place and distances to the nearest metre.
km/h to m/s at common speeds
| Speed | Metres per second | In 2 seconds | 200 m takes |
|---|---|---|---|
| 40 km/h | 11.1 | 22 m | 18.0 s |
| 50 km/h | 13.9 | 28 m | 14.4 s |
| 60 km/h | 16.7 | 33 m | 12.0 s |
| 80 km/h | 22.2 | 44 m | 9.0 s |
| 100 km/h | 27.8 | 56 m | 7.2 s |
| 110 km/h | 30.6 | 61 m | 6.5 s |
A quick rule for the field: at 60 km/h a vehicle covers about 17 m every second, and at 100 km/h it covers nearly 28 m. Double the speed and you double the distance per second, but stopping distance grows even faster because braking distance depends on the speed squared. The stopping sight distance calculator shows that part.
A worked example for a toolbox talk
A crew is working on the shoulder of a road with an 80 km/h approach. The first advance warning sign is 200 m upstream of the workers.
- Enter 80 km/h, a distance of 200 m and a look-away time of 2 seconds.
- 80 ÷ 3.6 = 22.2 m every second.
- In a 2-second glance at a phone the driver travels 22.2 × 2 = 44 m without watching the road.
- From the first sign to the workers takes 200 ÷ 22.2 = 9 seconds.
So a driver who passes the first sign and then looks at a phone for 2 seconds has used up almost a quarter of their warning distance before they look up. Nine seconds is all the time the crew has if that driver doesn't slow down. That's a strong way to open a talk about escape routes, lookouts and never turning your back on traffic. Our toolbox talk briefing checklist and the guide to work zone intrusions build on this.
Speed and Dimension D in NSW
Under Transport for NSW's TS 05492 Traffic Control at Work Sites (June 2026), most distances on a NSW work site are multiples of Dimension D. D is the speed of the zone drivers are in before the point you're measuring, read as metres. An 80 km/h approach gives D = 80 m.
The converter gives a useful way to picture it: at any speed, a vehicle covers D metres in 3.6 seconds. So 1.5D, the minimum sight distance to a traffic controller, is about 5.4 seconds of travel, whatever the speed.
D also lags one zone behind. In a run of zones of 100, 80, 60 and 40 km/h, D is 100, 100, 80 and 60 m, because each value comes from the zone before it. D is not used to set the length of a speed zone. Those lengths come from their own tables:
| Temporary speed limit | Minimum zone length (TS 05492 Table 27) | Transition zone (Table 28) |
|---|---|---|
| Under 40 km/h | 100 to 200 m | – |
| 40 km/h | 100 to 500 m | – |
| 50 or 60 km/h | 150 m | 150 m |
| 70 km/h | 200 m | 200 m |
| 80 or 90 km/h | 500 m | 300 m |
Transition zones should be longer where there's heavy traffic, a lot of heavy vehicles or a downgrade. A 40 km/h zone can run up to 2 km for spray-seal resurfacing. Our guide to work zone speed limits in NSW explains how the limit itself is chosen.
Queensland differences
Queensland's QGTTM Part 3 sits on top of the national Austroads guide (AGTTM) and works differently:
- The 200 m rule. For the first 200 m after a speed limit drops, sign spacing and tapers use the higher speed. A spacing that falls partly inside that 200 m uses the higher speed for its whole length.
- Sign spacing is 15 m up to 55 km/h, 45 m from 56 to 65 km/h and equal to the speed in km/h above that. A single advance sign goes at double the spacing.
- Speed by worker distance. QGTTM Part 3 Table 5.5 suggests 40 km/h where workers are within 1.2 m of traffic without a barrier, 60 km/h for 1.2 to 3 m, and 80 km/h for 3 to 6 m.
The converter works the same way in every state, because metres per second are just arithmetic. What changes is the distance the rules ask for. Victoria, WA and SA follow AGTTM with their own codes of practice, so check the approved TGS for the figures that apply.
Using the numbers safely
The converter tells you how far and how fast. It doesn't tell you what's allowed. Use it to:
- explain to a new starter why the escape route matters
- show a client why the first sign has to go so far back
- check how long a vehicle takes to reach a controller from the first point they can be seen
- picture what a look-away of 1, 2 or 3 seconds really means
For sight distance to a controller or queue, use the sight distance check. For sign positions, use the sign layout builder. And when the site doesn't fit the TGS, talk to the traffic management designer before changing anything: moving signs beyond the tolerances is a TGS change.