Though not new to weigh-in-motion (WiM) use for acquiring vehicle weights, Brazil has recently implemented changes to metrological standards and legislation that will lead to increased use of WiM. Faced with similar issues that weight enforcement officials experience in regions around the world, this forward-looking strategy aims to capture the benefits that WiM can offer the country’s transportation infrastructure.
In fact, “Brazil was one of the first countries in the world to use WiM”, says Douglas Gaspareto, engineer and public agent with ANTT, Brazil’s National Agency of Land Transport. ANTT is the federal agency responsible for regulating and supervising road transport of passengers and loads on federal highways and those operated by concessionaires in toll roads. Since the 1970s, strain gauge-based technology was used for screening for enforcement and subsequent weights on scales, he explains. The system is still used and the weighing is performed in two stages. First, a selective system separates vehicles that may be overweight. Second, the selected vehicles are weighed on low-speed axle scales with vehicle speeds between 5-12kph.
This process may look similar to that in other countries, where WiM technology is used as a mainline screening tool for enforcement. But Brazil has been using WiM for the low-speed weighing and ticketing of overweight conditions in addition to weighing on static scales. These sites experience the same problems posed to officials throughout the world - infrastructure costs and maintenance concerns for weighing facilities as well as challenges faced by enforcement staff that must cover one of the world’s largest countries with busy commercial traffic.
To address this, new metrological standards and legislation were developed to enable WiM to be implemented in greater scale and at faster speeds. Starting almost a decade ago, metrological regulations were proposed that led to extensive research and testing of high-speed weighing devices to understand their capabilities and how they could be used on existing and future roadways.
With 26 states in the country, there is a mix of jurisdictions responsible for road safety, including municipal, state and federal government agencies. Cooperation to research and develop WiM has included a variety of other organisations. Inmetro, the National Institute of Metrology, Quality and Technology, is responsible for the development of metrological regulations required for device accuracy and certifications for WiM systems. Meanwhile, Contran (Conselho Nacional de Trânsito / National Traffic Council) determines the penalties for enforcement when overweight conditions such as axle, axle groups and gross vehicle weight (GVW) limits are exceeded.
Development of new WiM standards took years. Universities, concessionaires and integrators operated field test sites to demonstrate real-world system performance and device accuracies. Intercomp’s high-speed strain gauge sensors have been installed throughout the country for this testing. WiM strip sensors are included in systems that demonstrated the performance and feasibility of the new standards to include high-speed WiM (HS-WiM). Having devices that meet the proposed standards was an important step to move theoretical discussions to practical implementation.
Standards
The new metrological technical regulation now active in Brazil builds upon the country’s experience with low-speed WiM (LS-WiM) as well as the performance demonstrated by HS-WiM systems. As written, the new accuracy classes for WiM system certification are speed unlimited. This allows for certification of systems to the appropriate class at whatever speed is achievable.
Drawing from the OIML R134 WiM standard, as well as prior Brazilian metrology and the years of experience and feedback from universities, operators and concessionaires, Inmetro arrived at type certification and in-service inspection thresholds. At system approval, performance must meet accuracies that are one-half of in-service inspection. For example, GVW accuracy classes of 2.5%, 3.5% and 5% allowed error have in-service inspection thresholds of 5%, 7%, and 10% respectively.
Similar to OIML R134, maximum permissible error (MPE) is used, so that all measurements must fall within the allowed error. For legal metrology, in Brazil and elsewhere, a high bar is set for performance for these applications.
Current and future weight enforcement still requires involving an official, as with other automated enforcement activities in Brazil. For example, speed enforcement and red-light violations are detected and processed by automated systems. But human verification is required before mailing an infraction notice to the vehicle owner. WiM systems will be no different. This underscores a benefit of automation and centralisation of the violation data – that a single enforcement official can remotely monitor widespread automated enforcement activities and act upon vehicle transactions that are verified.
With the expansion of WiM standards and their use in mainline or high-speed applications, integration into existing processes and locations will most quickly demonstrate the efficiency and effectiveness of WiM. Brazil already has interstate sites for transiting vehicles where cargo and vehicles are inspected and assessment of an ICMS tax - a state tax for goods and services - takes place. Sites placed upstream of these locations allow for rapid screening and identification of overweight vehicles and where further actions can take place. Overweight vehicles are ticketed up to 12.5% above maximum allowable limits for GVW or axle weights. But where conditions exceed 12.5%, the vehicle is required to stop and offload or redistribute the load to return to safe operating weight.
Concessionaires operating toll roads have a list of operational legal obligations which include monitoring speed and weights in alignment with the guidance of the federal agency ANTT. It’s in the concessionaire’s best interest to minimise transit of overweight vehicles for safety and roadway conditions. Many employ HS-WiM as screening tools, allowing vehicles to bypass fixed stations where weight, licensing and vehicle conditions are within safe and allowable limits.
While a concessionaire maintains the operating infrastructure, it will often employ ITS integrators to supply, install and maintain the equipment and sites that enable monitoring, classification and detection of transiting vehicles. One such integrator is FiscalTech, based in Curitiba and which provides ITS systems throughout Latin America and other regions. “Automation of ITS systems provides efficiency benefits to drivers, concessionaires and federal enforcement officials,” says Diego Hoffmann, director of operations and engineering at FiscalTech. “A driver either bypasses a station, is diverted for further inspection or, if necessary, can interface with a remote agent via a kiosk. In this way, a single official can remotely monitor and maintain a network of stations from a central location.”
Brazil’s 240,000km of roads is essential to maintain the nation’s robust economy. Implementation of HS-WiM for enforcement will protect and maintain the country’s growing infrastructure, notes ANTT’s Gaspareto. “By applying HS-WiM on a large scale it will be possible to increase the number of vehicles that are effectively weighed and not impair traffic flow. By using an effective and suitable weighing system, it is possible to reduce accidents caused by overweight [vehicles]…and reduce damage to the pavement.”
Jon Arnold is a market specialist with Intercomp, based in Messina, in the US state of Minnesota. He holds an MBA from Hamline University in St Paul, Minnesota, an MSc in chemistry from the University of Iowa in Iowa City and a BSc in chemistry from Augusta University in Augusta, Georgia. When not being a high-flyer in the WiM sector, he can be found high in the skies, either piloting a plane or skydiving from one. When down to earth, he teaches skydiving as an accredited Accelerated Free Fall Instructor (AFFI).
