Weigh in Motion: New Technology at CALAX

by Celina Joyce D. Lazaro, MARCH 2021

Have you passed on the CALAX expressway lately? Ever wonder what are the cameras attached to a gantry while driving on CALAX. This equipment is called Weigh in Motion or simply WIM. The weigh-in-motion can provide the vehicle information to our Traffic Control Room. The information includes vehicle class, vehicle speed, vehicle weight, and vehicle license plate.

Expressways play a crucial role in the transportation of people and goods all over the world. Overweight vehicles cause enormous damage to road structures and this equipment, weigh in motion, can catch the overweight vehicle even at high speed.

Figure 1. Vehicle in motion can be captured by WIM cameras.

Weigh-in motion or WIM devices are designed to capture and record axle weights and gross vehicle weights as vehicle drives in the weighing pads embedded in our carriageway. Compared to static weigh stations, this WIM device can weigh the vehicle at normal traffic speeds and does not require the vehicle to stop or drive at a low speed, this makes the WIM devices more efficient compared to the old static weighing stations.

How Weigh in Motion works?

Weigh-in-Motion uses ALPR cameras, WIM sensors, data logger, WIM software, and WIM server. The Weigh-in-Motion is integrated with ALPR cameras to capture the vehicle plate number. WIM also provides the vehicle’s data such as vehicle class, vehicle weight, and vehicle speed. This information can be viewed in the WIM software application that is managed by the Traffic Control Room personnel. 

ALPR Cameras

Figure 2. Actual WIM Cameras installed in CALAX.

The cameras of WIM are Automatic License Plate Recognition (ALPR) cameras wherein the plate number of the overweight vehicle will be captured by these cameras. Each ALPR camera is installed in each lane of the expressway. The plate number of the overweight vehicle will send to the WIM application and will be viewed in the Traffic Control Room.

WIM sensors

The WIM sensors are installed on the road pavement and provides measurement signals. The WIM sensor can measure the wheel and axle loads and determine the vehicle’s gross weight under rolling traffic conditions. When an overweight vehicle passed on the sensor, the sensor will be triggered, and the ALPR camera will capture the overweight vehicle. The plate number of the overweight vehicle will also pop up in the Variable Message Sign (VMS) installed after the gantry of WIM. The information gathered will be sent in WIM application software.

Data Logger

The data logger is a data processing unit specifically designed for WIM sensors. It allows the users to monitor traffic in real-time and gathers vehicle data. It can monitor up to four traffic lanes and able to measure up to 50 tons of axle load. The data logger for the WIM sensor can detect single or dual tires of vehicles and provide high weighing accuracy (OIML R134 Certified).

WIM Software Application

The WIM software application is a software module that is integrated with Traffic Management Control System (TMCS) software. As an integrated centralized software, the operator can generate the vehicle data including the captured image to the authority to facilitate law enforcement to overweight vehicles. The interface of WIM shows the weight of a vehicle and also the speed of the vehicle passing through the WIM sensor. The extra information such as vehicle class, the actual time of the vehicle passing the WIM sensor will be displayed in the interface. 

WIM Server

The WIM server will be the one to store the information given by the WIM sensor. 

Figure 3. Weigh-in-Motion at night in CALAX

The Weigh-in-Motion technology will be beneficial since this will bring high processing rate, safety, continuous data processing, minimum scale avoidance, and dynamic loading of data. The processing rate of trucks can be weighed as they travel at highway speeds, resulting in a significantly greater number of counted vehicles in a short period compared to static weighing stations. The safety of our traffic personnel will also be one of the benefits of the implementation of this technology. The continuous data processing of WIM can be performed in real-time rather than static weighing. More sites can be monitored with the WIM software application at the same time using the WIM application software. WIM can also record dynamic axle load information compared to static weighing stations that gather static information only. Overweight vehicles are not only hazardous for highway infrastructure; their chances of accidents also increase by a large factor. The implementation of Weigh in Motion technology in our expressway will support us to a more efficient and effective way of maximizing our new technologies.

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About the writer:

Celina Joyce D. Lazaro. Simply Celine. Graduated as a Computer Engineer in Bulacan State University and current position as Toll and Traffic Systems Associate. Bubbly but shy. Finds peace in quiet places. Also an optimist.

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