SW-Defined Free-Flow WIM Enforcement
CAMEA's in-the-field experience with WIM direct enforcement shows that reaching the free-flow measurement is, above all, about a SW support for measurement and its validation.
Problematic Behavior at WIM Stations
CAMEA long term in-the-field experience with WIM enforcement shows that once drivers understand the mechanism of the measurement, many will immediately try to avoid the pressure sensors when passing through a WIM station. Therefore, there is a strong need for measurement “validation” - correct detection of all problematic maneuvers that vehicles perform, as well as for a “free-flow” approach - weighing in the whole width of the road (between the marked lanes, on the hard shoulder etc.).
Solving the problem of drivers avoiding weighing requires a comprehensive approach including sensor installation layout, system calibration and, above all, SW support for measurement and its validation.
Reality of Covering the Whole Road Width
Solving this problem requires a comprehensive approach including sensor installation layout, system calibration and, above all, SW support for measurement and its validation. At first glance it seems logical to cover the entire roadway with sensors, even in one piece. Unfortunately, real-life conditions usually don’t allow that, due to the slope of the road and construction specifics, such as dilatation and construction joints. The gaps between the sensors will appear and the free-flow measurement will be SW-defined.
The overwhelming majority of vehicles can still be properly weighed. Some vehicles are not properly weighed - but they are still clearly identified. This is as close to the free-flow WIM as it gets.
Free-flow Weighing under Real-life Conditions
CAMEA WIM is certified for direct enforcement in the Czech Republic. Therefore, it needs to meet high requirements, although the goal is always to exceed them. Apart from sensor technology independence, it can weigh vehicles driving in both directions and, generally, detect various maneuvers that complicate the measurement – bypassing on a bi-directional road, driving between lanes, changing direction abruptly and acceleration with deceleration.
These features were tested by and independent highway authority in 2019 with no error, proving the capability of the free-flow weighing under real-life conditions. The test used two different vehicles, repeating each of the problematic maneuvers 10 times to ensure all are detected.