Weigh-in-Motion: Legally Compliant Dynamic Truck Weight Inspection System

SysTec Supplies Weighing Controllers and Software for the Rur-Scholle-Süd Weigh-in-Motion Project

SysTec weighing controllers and software are being used at the dynamic truck weight inspection station on a German highway. The new weigh-in-motion system is located at the Rur-Scholle-Süd rest area on the A4 highway and sets new standards for protecting transportation infrastructure. The goal of the pilot project is to detect overloaded trucks and inspect them in compliance with legal requirements — without unnecessarily disrupting traffic flow.
 
The dynamic weighing system was implemented by SysTec's partner Waagenbau Dohmen GmbH. Key components of the weighing solution include the W&M approved SysTec weighing controllers (IT8000E and IT1) and SysTec software solutions. They ensure legally compliant weight recording, precise processing of measurement data, and seamless integration into Autobahn GmbH’s* digital weight control system.

The pilot project on the A4 is the first of a total of 16 planned weigh-in-motion systems that Autobahn GmbH and the BALM (Federal Office for Logistics and Mobility) have planned. These control systems are to be implemented throughout Germany in the coming years.

*Autobahn GmbH is Germany’s federally owned highway administration company.

Every day, thousands of trucks travel on Germany’s highways. Many bridges and roadways were originally designed for significantly lower traffic and axle loads than what are common today. The A4 highway, in particular, is one of Europe’s most important freight transport routes. A large portion of the traffic from the ports of Rotterdam and Antwerp travels via the A4 and the Eifeltor Bridge, which was not originally designed to handle these loads. Overloaded trucks cause damage to the infrastructure, shorten the service life of bridges and roads, and simultaneously increase the risk of accidents due to longer braking distances and altered driving dynamics.

Until now, overloading could only be checked on a random basis. Selecting vehicles was a time-consuming process that required significant staff resources, resulting in two to three inspection weighings per day. With the new digital weight-checking system, Autobahn GmbH and BALM are therefore adopting a new approach: Overloaded trucks are to be automatically detected, specifically diverted, and then weighed in compliance with legal requirements. This allows for weigh-ins every minute.
 

The weight inspection station operates using a two-stage inspection process. Several kilometers before the inspection point at the Rur-Scholle-Süd rest area, sensors embedded in the roadway detect all trucks in moving traffic and determine their weight values (at this first stage, the weight control is not yet legally compliant). Suspicious vehicles are automatically identified at this stage. The measurement in moving traffic serves exclusively for preliminary screening.

In the next step, an automatic video license plate recognition system assigns the measurement data to the respective vehicle. LED display boards direct the affected truck specifically to the rest area. 

Finally, at the inspection station, the legally compliant dynamic truck weighing takes place using a combination of vehicle scales based on SysTec weighing electronics. Only this W&M approved weighing provides the legal basis for regulatory measures such as fines, transshipments, or driving bans.

The weighing system consists of three combined truck scales. Two weighbridges, each approximately 20 meters long, are supplemented by an axle load scale approximately 80 centimeters long. Beneath this axle load scale is an additional measuring device that determines the position of the wheel center during the drive-through. This allows the actual axle position to be determined precisely and further increases measurement accuracy.

The central evaluation electronics consist of the SysTec IT8000E weighing controller. It processes all measurement data from the connected scales. Several independent SysTec weighing systems handle the fast and highly precise weight determination for each individual scale as well as the recording of axle spacings.

The combination of multiple independent scales enables particularly reliable weight determination. At the same time, the system automatically recognizes different vehicle and axle combinations based on the axle distances and correctly assigns the measured values.

The system is supplemented by custom-developed PC software from Dohmen. This software enables communication and visualization with the higher-level BALM system.

The scale combination supports two operating modes: dynamic and static. Weighing is performed dynamically during a slow pass at a speed of approximately 5 to 12 km/h. For vehicles with shifting loads—such as tanker trucks or livestock transporters—static weighing can be performed alternatively to ensure the highest possible measurement accuracy even under these conditions. The system is designed for vehicle weights up to 70 metric tons.

Since the measurement results form the basis for regulatory actions, the highest standards of accuracy and traceability apply. The weighing system meets the requirements of the international recommendation OIML R134 for automatic road vehicle scales. It achieves accuracy class 2 for gross weight and accuracy class E for axle groups.

In dynamic vehicle weighing, measurement deviations can arise from intentional or unintentional driving behavior as well as from external influences. For example, braking and acceleration maneuvers or environmental factors can affect the measured vehicle weight. The W&M approved weighing system at the Rur-Scholle-Süd pilot station reliably detects these influences. 

A key feature of the solution is redundant weight determination. The total weight and axle load weights are calculated using multiple independent measurement systems and cross-validated against one another. This multilayer verification enhances measurement reliability and ensures legally compliant weight determinations during regulatory inspections.