Manual / Overlays

Live congestion

How the roads are running right now, from the road authority's own measurements. The overlay to reach for when a route is about to run late for a reason the timetable cannot see, or when the alternative road for a diversion may already be jammed.

What you are looking at

Switch on Traffic in the Layers panel and road links are drawn in a green-to-dark-red scale: free-flowing at the green end, blocked at the dark end.

Along the bottom of the map, the Traffic congestion block carries the whole key:

• the colour ramp, with free flow at one end and blocked at the other;
• a no data swatch;
• a last known, not live swatch, drawn dashed;
• hover a road for its measured travel time;
• an Only congested roads box, which says under it (hides free-flowing and no-data);
• and, at the top right of the block, how many links are on screen and when the reading was taken — 2,847 links · as at 14:30.

Three ways a road can be drawn, and they are three different facts:

Hover any link and you get its name and direction, its congestion score out of seven, its speed, and how much slower it is than its own free-flowing time — +2 min vs free flow.

What the numbers mean

What they do not mean

It is not a measurement of your bus. No route, no run and no timetable is involved anywhere in this overlay. A red road does not say a bus on it is late; it says the road is slower than that road's own normal. What the bus is doing is the bus dot's business, and the two scales share nothing — not the colours, not the bands, not the arithmetic.

A score is relative to its own road. 5 out of 7 on a suburban arterial and 5 out of 7 on a freeway are the same statement about two very different roads. There is no absolute speed behind the number.

Grey is not "clear". It means nothing was measured and nothing recent enough could be carried. A quiet road with too few passing devices to measure looks exactly like a road nobody is reading. Grey links are also removed by Only congested roads, which is why that box says it hides them as well as the free-flowing ones.

A dashed road is a memory with an age on it. It is the last colour that road was known to be, kept for a while so the map does not forget what it knew a minute ago. It is not a claim about now. When more than half of what is on screen is dashed, the bar says so — read the whole picture more carefully at that point.

"As at 14:30" is the reading, not your clock. The measurements refresh every few minutes, so the overlay is a recent observation rather than live truth.

The score is bounded and occasionally strange. It is published as 0–7 and the app holds it there. It is somebody else's index, not a figure this app computes, and nothing in the app checks it against reality.

There is no history. The app keeps no record of what a road was doing an hour ago, so "was this corridor jammed at 08:00 yesterday" is not a question this screen can answer.

The licence, and why it is your business

The traffic measurements come under a different licence from everything else on this map: a non-commercial one. The credit in the map's bottom-right corner says so as you read it:

Traffic: Transport Victoria Bluetooth Travel Time (CC BY-NC 4.0)

Two practical consequences:

• Switching the source on at all is the deployment owner's decision, not a default. That is why the Traffic tile is simply absent on a deployment that has not taken it up — the licence has to be accepted deliberately.
• What you take off this overlay carries that licence with it. A screenshot of a congested corridor pasted into a commercial report is not the same as one of the incident overlay beside it, which is published under an ordinary attribution licence with no such clause. If you are unsure whether what you are producing counts, ask before you publish, not after.

The credit for each overlay is worded for its own licence, which is why they read differently and why one caveat never gets applied to the other.

When it looks wrong

There is no Traffic tile. This deployment has not been given the source. It is a setup and licensing question — ask whoever administers it.

The bar says it is waiting. The line reads:

Waiting for the first poll…

A poll is the app going out to ask the source for a fresh reading. The part that concerns you is the rest of it: traffic is switched on for this deployment and no reading has come back yet. Give it a few minutes.

The bar says Traffic feed unavailable. The fetch is failing rather than merely being slow. That one will not fix itself; tell whoever runs the deployment.

Half the map has no lines. Coverage is partial by nature — this measures links the authority has readings for, not every road. Empty is not "clear".

Everything is dashed. Nothing new has arrived for a while and you are reading memory. Check the as at time in the bar.