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Weigh-In-Motion

UnicamWIM

Weigh-In-Motion - UnicamWIM

The UnicamWIM system is a state-of-the art solution for a variety of high and low speed Weigh-In-Motion (HS/LS-WIM) applications as defined by international standards (e.g. COST323, ASTM E1318). It measures and records weights of wheels, axles and vehicles (gross) passing over weighing sensors embedded in the road pavement. All measurements are done at normal traffic speeds, so complete vehicle weighing (wheels, axles, gross) can be performed without any traffic flow disturbances. The system has been certified for direct WIM enforcement (type approval certificate valid in the Czech Republic).

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Additional Features

The system is designed for true multi-lane bi-directional free flow measurement and verifies the accuracy of all measured parameters of the vehicles in both road directions and also when driving between road lanes.

The accuracy of weighing may be lowered by nonstandard vehicle behavior (acceleration, deceleration, lane traversing, shoulder driving etc.) or other influences (bad vehicle or road conditions, uneven weight distribution etc.). So to determine whether the measured values are in the defined accurate class, the system provides advanced measurement validity evaluation.

The system can be combined with other ITS systems such as spot/section speed enforcement systems, dimensionin- motion (using a 3D scanner), vehicle search etc.

Highly accurate traffic classification and data collection is available.

Estimation of road ruts and sensor surface wear can be calculated from the collected data, so load equivalence factor evaluation can be provided (ESAL, AASHTO).

Applications

The system applications are as follows (gross weight, confidence level π = 95 %):

  • for enforcement the tolerance δ is 5-7 %, accuracy class A(5) or B+(7)
  • for pre-selection the tolerance δ is 10-15 %, accuracy class B(10) or C(15)
  • for statistics the tolerance δ is 15-25 %, accuracy class D+(20) or D(25)

Basic Specifications

The certified direct enforcement version of the system has the following parameters (Czech Republic):

  • Confidence level: π = 95 %
  • Speed range: 20 – 100 km/h
  • Gross weight: δ = 5 % (>3.5 t)
  • Group of axles, single axle, axle of a group: δ = 11 % (1 – 20 t)