Weighing-in-Motion (WIM)
There are four popular weigh in motion technology in the world: quartz sensor, piezoelectric, bending plate and loadcell. In particular, the quartz sensor technology is recognized suitable for a wide range of weather conditions, vehicle speed can be ranged from 1Km/h to 230Km/h, high accuracy, up to 98%. So this technology has being applied in many countries around the world.
The Weighing-in-Motion (WIM) system was introduced in the United States in the mid-1950s, since then there have been many developments and different applications in the world. In the early days, static scale were set up on vehicle weighing stations to check, detect and force overloaded vehicles to unload. However, due to the increase in truck traffic while the capacity of the vehicle weighing stations are limited, it caused congestion and trouble at the vehicle weighing stations. And this makes it impossible to control the full and exact load of overloaded vehicles.
WIM systems are widely used worldwide, from developed countries to developing countries. By 2006, the number of WIM lanes in North America was the highest in the world (3,864), followed by Asia (1,700), Latin America (1,208), Europe (1,188) ), Australia (120), Africa (88) and Middle East (56).
A WIM system consists of the following main components:
- Weighing Sensor: have sensor functions and converts the forces caused by axial load into electrical signals. Each lane is equipped four quartz sensor bar connected directly to the Data Logger located in the control cabinet. The signals received from the quartz sensors will be transmitted to the data logger for processing.
- Vehicle detectors: Includes magnetic rings and magnetic detectors. Magnetic ring installed in the lane near the quartz sensor location, connected to the magnetic detector located in the control cabinet for signal processing. The output signal of the magnetic detector will be transmitted to the data logger
- WIM data logger: Directly connected to the weighing sensor, magnetic detectors to collect vehicle load data as the vehicles move through the quartz sensor area. From the data on the recorded force, the data logger will calculate the axle load, then will calculate the total load of the vehicle.
- Vehicle number plate recognition camera: has the function to collect information about vehicle number plate. As a result, when detecting a violate vehicle, functional forces will have sufficient information on the load and number plate to enforce the overloaded vehicle off the route.
- Lane watch camera: It has the function of capturing the image of the vehicle when it passes through the weighing area. In order to help the functional forces have sufficient evidence as well as the identification of vehicles in violation.
- VMS Electronic Signs: It’s an electronic LED sign which is programmable and able to remote control on the Ethernet, informing the load or number plate of vehicles with the signs of load violation.
- Processing computer: Collect information from data logger and surveillance camera systems. The collected information will be packaged and send to the weighing controlling center (if available) or used to monitor real-time weighing data.
The system that uses quartz sensor is high stability. The measurement efficiency of quartz sensors is very stable over the life of the WIM system, minimizing maintenance costs and minimizing traffic congestion if maintenance of the weighing system is required. At the position of installed weight, with the standard road surface thickness over 60mm, the installation of sensors will not affect the quality of the road surface.
For vehicle weighing technology using quartz sensor which has being deployed, load information of overloaded vehicles is displayed on the VMS electronic sign immediately when the vehicles go through automated weighing system. Moreover, all image information, detailed data about the load of all vehicles passing weighing stations are transferred to the data center. Overloaded vehicles will be alerted the status and added into a list which will be sent to the functional force for further processing. Weighing results can be used to penalize the violated vehicles, to reduce the number of violations.
Statistic scale
For statistic scale, the US Intercomp handheld scales is recognized high precision, high stability, compact design, integrated wireless communication and able to use solar power, very convenient to use in Vietnam roads. It consists of the following items:
WIM LS630 scale
LS630 is designed for use in pair and supports both wired and wireless interfaces.
PT20 WIM standalone display
This standalone display will display and store all information of all weighed vehicles when connected to the LS630 scale pair. The parameters such as the weight at the wheels, the weight at the axles, the total vehicle weight, distance between axes, and vehicle speed are recorded. The results are displayed on a 5.7 "LCD screen and this display can store information of up to 2000 vehicles pass. Data can be exported to Intercomp WIM software or to other devices via USB or RS232. The device is also equipped with a thermal printer for printing information of weighed items.
Monitoring vehicle load will bring both social and economic benefits for investors, vehicle owners and road management agencies. Road management agencies not only reduce the costs of repairing roads and bridges, but also save money on mobile weighing stations and manpower for manual toll stations. In addition, this technology also help to reduce harmful emissions, increase engine life expectancy and help authorities to manage vehicles effectively.
