Insights
Camera-based SAT or inductive loops?
An inductive loop measures vehicle passage at one point in the pavement; a camera with computer vision measures volume, class, axles, speed and density from the CCTV that already exists, with no roadworks. In many projects the camera replaces the loop; where specific metrological requirements apply, the two methods work together.
Two ways to do SAT
In the terminology of ARTESP, the São Paulo state transport regulator, and ANTT, the federal one, SAT is the automatic traffic sensor (Sensor Automático de Tráfego): the equipment that counts and classifies vehicles by lane and records speed. For a long time, that meant an inductive loop cut into the pavement. Omnivias SAT performs the same function with the highway’s cameras, using computer vision.
| Dimension | Inductive loop | Camera-based SAT (Omnivias) |
|---|---|---|
| Installation | Pavement cutting and lane closure | Uses existing CCTV; no roadworks |
| What it measures | Passage, occupancy and speed at the loop point | Volume, class, axles, speed and V85, density, headway and HCM parameters |
| Visual context | None | The image shows what happened and allows the count to be audited |
| Maintenance | Wears with the pavement; resurfacing requires reinstallation | Remote updates and calibration |
| Incidents | Does not detect them | The same camera feeds DAI |
| Adverse conditions | Little affected by light and rain | Calibrated per camera for night, rain and reflections |
| Validation | Depends on sensor and installation | Comparison against the reference agreed in the field |
When the camera replaces the loop
When the camera frames the lanes well, is stable and has enough light at night, computer vision delivers counts by class continuously. In Omnivias projects in production, counting accuracy runs above 95% against the reference agreed in the field.
When to use both
At points with specific metrological requirements, such as weighing or enforcement, or when the contract calls for certified equipment in the pavement, the loop stays. The camera adds visual classification, an auditable time series and incident detection at the same point.
Classified volumetric counting
This is the count broken down by vehicle class, lane, direction and period. The classes follow what the contract or the regulator calls for (cars, trucks by number of axles, buses, motorcycles), and SAT delivers reports with calculation records.
See also: SAT, the camera checklist and the glossary.