# Applying Machine Learning to Preselective Weighing of Moving Vehicles
## 1 Introduction and Status of the Issue
Each sensor typically comes with a shielded signal cable featuring reinforced outer insulation to protect against mechanical damage and electromagnetic interference. The standard length  
Figure 1: Scheme of the WIM system (source: own study). of the cable is 40 m. The cable is routed in a groove to shield it from external influences, especially moisture. At the exit from the outermost weight sensor, toward the roadside, the cable is encased in a steel tube, laid parallel to the drainage pipe, and routed to a telecom manhole located at the roadside. As their name implies, preselection scales are used only for statistical purposes and for typing potentially overloaded vehicles for precise, static inspection. Thus, it becomes necessary to carry out precise, static inspection of vehicle weights outside normal traffic conditions, at measuring stations set aside for this purpose. There are a number of new problems here that affect the entire process. First of all, it is not possible to carry out such an inspection on the main road, and requires the creation of some kind of siding where the inspection can be carried out under conditions that are safe for drivers and inspectors. This location should be a short distance from the preselector weighing scale to prevent the checkpoint from being bypassed. On the other hand, however, the distance must not be too short, as the checkpoint staff must have time to react and safely stop a vehicle that can travel at speeds of up to 90 km/h. Scales used in the inspection process are produced by many companies, but they share common features and are united by the same legal standards. An example is the WWS-type portable two-bridge scale, which is structurally designed and metrologically approved for weighing vehicles using the dynamic method, i.e., while the vehicle is moving at a speed of 1-5 km/h. The weighing process is therefore subject to the relevant regulations on the requirements to be met by vehicle scales for weighing vehicles in motion, as well as the detailed scope of tests and checks performed during legal metrological control of these measuring instruments. The most complex issue concerning WIM systems is accuracy, particularly regarding the standard piezoelectric sensors used in these systems. Several factors affect measurement accuracy, including vehicle speed and trajectory, vehicle class (type), pavement temperature, and air and pavement humidity. Consequently, sensor accuracy can depend not only on weather conditions and the vehicle being inspected but also on the measurement system's location. For OIML R134, there are six accuracy classes for measuring the total weight of a vehicle, each corresponding to specific maximum permissible errors during system operation: 0.2 (0.2%), 0.5 (0.5%), 1 (1%), 2 (2%), 5 (5%), and 10 (10%). For axle load measurements, six accuracy classes and their corresponding errors are specified: A (\(\pm\)0.5%), B (\(\pm\)1%), C (\(\pm\)1.5%), D (\(\pm\)2%), E (\(\pm\)4%), and F (\(\pm\)8%). During system calibration and legalization, the permissible measurement error is set at 0.5 of the maximum permissible error under operational conditions. The accuracy of WIM systems varies in different parts of the world due to diverse climatic conditions [13]. It is well known that these factors can cause significant changes in the accuracy of vehicle weighing within very short periods, sometimes less than one hour [14]. Addressing this issue is possible by developing and implementing advanced algorithms and methods for WIM system self-calibration [15] or by augmenting WIM systems with machine learning algorithms. Moreover, WIM-E systems are the most effective for protecting road infrastructure because they eliminate the need to stop vehicles to impose fines. In such cases, measurement certification by a measurement office (similar to speed cameras or section speed measurement systems) is required to ensure the results are binding in administrative proceedings for imposing penalties.