Tracking & Mapping Private Cars in Real-Time

OpenTrafficMap is a real-time animated map showing the movements of cars, trams and buses in Graz, Switzerland. It also shows the current status of all the city's smart traffic lights - displaying whether signals are red or green.

What is OpenTrafficMap?

Modern vehicles and road infrastructure increasingly use C-ITS (Cooperative Intelligent Transport Systems), a wireless standard designed to improve road safety and traffic efficiency.

Cars, buses, trams and traffic lights can broadcast messages containing data such as:

• vehicle position
• speed and direction
• braking or acceleration status
• traffic signal phases
• intersection lane geometry
• roadworks and hazard alerts

OpenTrafficMap is an open-source platform that listens to these broadcasts and turns them into a public live animated map.

Live Trams, Buses and Traffic Lights

Because Graz’s trams and buses broadcast their positions, OpenTrafficMap can show live tram and bus locations, route numbers and destinations, and the current speed of vehicles. The project also maps smart traffic lights, displaying whether signals are red or green, light countdown timers and lane turning permissions.

Tracking Private Cars

There are already lots of applications that show city public transit vehicles moving on a live map. However this is the first time I've seen a map tracking the locations of private vehicles - which obviously raises lots of privacy concerns. 

OpenTrafficMap is able to display the locations of some private cars because many newer vehicles broadcast Cooperative Awareness Messages (CAMs) over the 5.9 GHz C-ITS network. These safety messages are designed to let nearby vehicles and roadside infrastructure know where a car is, how fast it is moving, and which direction it is travelling. 

By placing receivers around the city, the OpenTrafficMap team can capture those broadcasts and plot the transmitted GPS coordinates on a live map. Car manufacturers try to protect privacy by regularly changing identifiers such as MAC addresses and digital certificates, making continuous tracking harder. However, while a car is actively broadcasting within receiver range, its current position can still be shown in real time, allowing OpenTrafficMap to visualize moving private vehicles alongside buses, trams and traffic lights.