WIM systems are used in various ways to assist in the enforcement of the legal limits for vehicle loading or weight enforcement:
- Statistics and Planning
- Pre-selection for road side control
- Company Profiling
- Direct (automatic) weight enforcement
1. Statistics and Planning
In this application the data measured by a WIM system or a network of WIM-systems is used to generate statistical overviews on the loading situation on a specific road or a road network. Enforcement agencies can use these overviews in the planning of enforcement activities, when and where their control units are deployed. The statistics may also be used for the evaluation of the effects of enforcement activities. The main advantage of using WIM this way is that it allows enforcement agencies to focus its limited resources at the peaks in the overloading both in time and place.
The WIM system weighs all passing vehicles, when it detects an overloaded vehicle, an image of the vehicle is taken and the target vehicle is guided to the “dedicated weighing area”. At the “dedicated weighing area” the selected trucks are weighed by a weighing instrument that is legally accepted for enforcement, generally a static weighing scale or Low Speed WIM.
The main advantage of this application is that the hit-rate (the percentage of checked trucks that are actually overloaded) increases to more than 95%. This results in more efficient controls because only overloaded trucks are checked. It also gives an advantage to ‘good’ transport companies since almost no correctly loaded vehicles are stopped. Finally the information from the WIM can also be used for Statistics and Planning.
3. Company Profiling
All data measured by a network of WIM systems, including the pictures of the suspicious overloaded vehicles is stored in a database. Based on this information transport companies are selected that qualify for further action by the enforcement agency. This action may vary from the sending of a warning letter, a visit of the company for an inspection or further legal action.
The advantages of this way of enforcement are that the enforcement activities are directly aimed at compliance of loading regulations and preventive or incentive actions instead of writing tickets only. Since the focus is only on “problem” transport companies a relatively low number of enforcement personnel is required. Finally the effect of the enforcement efforts is not limited to the area directly around the WIM systems.
4. Direct Enforcement
In this application of WIM the evidence for the prosecution of an overloaded vehicle is directly based on the measurement by the WIM system. The procedure from the WIM measurement to prosecution can be completely automated and is similar to that of automatic speed enforcement.
This type of enforcement systems can be operational 24/7 without any enforcement personnel and is specifically suitable for highways with a high volume of trucks. The advantage is that all passing vehicles are controlled and most overloaded trucks are detected.