WIM Standards

NMi WIM Standard

Together with the Dutch Metrology Institute (NMi) Corner Stone International has taken the initiative to bring together a group of key-experts on metrology and standardisation together with a select number of international specialists in WIM to develop a new WIM standard. It is intended to be practical, easily accessible, widely acceptable, objective and independent for technology or commercial bias.

This NMi-WIM-standard  is open to be used by both buyers and vendors of WIM systems to facilitate their mutual relation (e.g. as a reference in tenders) and that with national regulators. It may also be used by any National Metrology Institute or Bureau for Weights and Measures in any country as a basis for national legislation.

The standard may be used free of charge and can be downloaded below or at the  the NMi website (www.nmi.nl). After registration you will receive a personalized copy of the document. This website also provides information on updates, additional background information, reference projects, etc.

International WIM Standards

Internationally, there are four standards that are regularly used as references in WIM projects:

  • COST-323; European WIM Specification [COST-323]. This includes a description of various procedures to test the performance of WIM systems and divide them into accuracy classes. Furthermore, requirements are specified for the selection of suitable locations for WIM systems, including requirements for the construction and flatness of the road surface. The document is intended as a reference for scientific research of WIM systems, not specifically for acceptance testing and certainly not for direct enforcement;
  • ASTM-E1318; the American Specification for Highway Weigh-In-Motion Systems [ASTM E1318] prepared by the American Society for Testing and Materials (ASTM). This is more or less the American counterpart of the European COST-323. The document is intended as a guideline for acceptance testing of WIM systems and as an independent reference procedure in the relationship between seller and user when purchasing WIM systems;
  • OIML-R134; Recommendation for Automatic Instruments for weighing road vehicles in motion [OIML R134]. This standard was drawn up by the International Organization for Legal Metrology (OIML) and can serve as a basis for direct enforcement. However, the current version of the R134 has been developed for semi-static and low-speed WIM systems in a controlled weighing environment, i.e. without considering the effects of vehicle dynamics. A project has been underway within the OIML since 2019 to overhaul the R134 and make it suitable for direct enforcement under high-speed, free-flow highway conditions.
  • NMi WIM Standard [NMi-WIM]. This document includes specifications and test procedures for statistical applications (such as road tax and pre-selection) and legal applications (such as direct enforcement and toll collection) and for both low-speed and high-speed WIM systems. It is more or less the industry standard, but is still used to a relatively limited extent in international metrology for direct enforcement.

It is important to note that all international standards mentioned currently only serve as a basis for implementation in national standards and legislation. Each country is free to establish its own national standard for testing and approving (homologation) WIM systems for direct enforcement. In current practice, the various national standards are based on parts of one or more of these international standards, but each has specific national adjustments.

How can Corner Stone assist?

When you are an End-user of WIM; we can assist with the integration of one or more of the international standards as part of your strategy for implementation of high speed, free flow WIM systems for direct (automatic) weight enforcement and/or for direct tolling by weight in your country or region.

When you are a Manufacturer of WIM; we can assist you with the preparation of your WIM system for the procedure of type approval required for certification according to the OIML-R134 and/or NMi WIM Standards. This way you will know what to expect when starting the certification process and will have a higher chance of success. Corner Stone can also guide you through the certification process including the laboratory and field tests. The tests for type approval themselves will be done by a National Institute for Legal Metrology (e.g. the NMi).