Video-based measurement systems for speed and distance record the traffic situation either for on-line or for off-line analysis of the speed of a vehicle and its distance to a vehicle in front. In order for this to work reliably the geometry of the road to be monitored is first surveyed in detail. In a second step the traffic scene along this stretch of road is recorded with a fixed camera (for instance, mounted on a bridge crossing the road). Using the geometry data, the events witnessed in the video images can be transformed in real-world coordinates using a mathematical transformation of perspective.
Vehicle speed is measured by monitoring the distance that the vehicle travels between the traffic situations depicted in two selected video frames. Likewise, the distance between two vehicles can be determined using the geometric transformation of the vehicle positions extracted from a video frame. Time intervals can be computed from the number of intervening video images using the known frame rate of the camera.
List of approved devices (as of January 2020):
| Manufacturer | Adress | Type designation/ Type approval mark |
 VIDIT Entwicklungs- und Vertriebsgesellschaft mbH | Gahlenfeldstr. 4a 58313 Herdecke | Verkehrs-Kontrollsystem VKS 3.0 18.19 / 01.02 |
| VIDIT Entwicklungs- und Vertriebsgesellschaft mbH | Gahlenfeldstr. 4a 58313 Herdecke | Verkehrs-Kontrollsystem VKS 3.01 stationär 18.19 / 04.01 |
| Vidit Systems GmbH | Am Ockenheimer Graben 40 55411 Bingen am Rhein | Verkehrs-Kontrollsystem VKS 4.5 DE-19-M-PTB-0029 |