How traffic and road cameras work

Most of the cameras on opencam belong to road agencies. They are not there for surveillance of people; they exist so that traffic operators can see congestion, incidents and road conditions without sending a patrol, and so the public can check a route before driving it.

Where they are

Road cameras sit on gantries, poles and bridges along motorways, at major junctions, in tunnels and on mountain passes. They are concentrated where traffic is heavy or weather is dangerous, which is why a single stretch of motorway can have a camera every kilometre while a quiet rural road has none.

Why the pictures look the way they do

• Low resolution on purpose. A traffic operator needs to see whether lanes are moving, not read number plates. Many agencies publish deliberately small images, and some blur or crop them.
• Snapshots, not video. Publishing a still every few seconds serves thousands of viewers at a fraction of the cost of video. See why a camera shows a still image.
• Wide angles. Cameras are aimed down the road to show queues building up, which is why vehicles look tiny.

What the agencies publish them through

In North America most road cameras are published through 511 traveller-information systems — a phone number, website and data feed that each state or province runs. European countries usually publish through a national open-data portal. opencam reads those same public feeds, so the camera you see on the map is the one the agency shows on its own site.

Reading a road camera well

1. Look at the lanes in both directions — a queue on one side and an empty road on the other usually means an incident.
2. Check the road surface: a dark, shiny surface is wet; a uniform grey can mean snow or slush.
3. Compare two or three cameras along the same route before deciding it is clear.