View source for Engineering:Weigh in motion

{{short description|Device designed to capture and record a vehicle's axle weights and gross vehicle weights}}
'''Weigh-in-motion''' or '''weighing-in-motion''' ('''WIM''') devices are designed to capture and record the [[Engineering:Axle|axle]] weights and gross vehicle weights as vehicles drive over a measurement site. Unlike [[Engineering:Weigh station|static scales]], WIM&nbsp;systems are capable of measuring vehicles traveling at a reduced or normal traffic speed and do not require the vehicle to come to a stop. This makes the weighing process more efficient, and, in the case of commercial vehicles, allows for trucks under the weight limit to bypass static scales or inspection.

== Introduction ==
Weigh-in-motion is a technology that can be used for various private and public purposes (i.e. applications) related to the weights and axle loads of road and rail vehicles. WIM systems are installed on the road or rail track or on a vehicle and measure, store and provide data from the traffic flow and/or the specific vehicle. For WIM systems certain specific conditions apply. These conditions have an impact on the quality and reliability of the data measured by the WIM system and of the durability of the sensors and WIM system itself.

WIM systems measure the dynamic axle loads of the vehicles and try to calculate the best possible estimate of the related static values. The WIM systems have to perform unattended, under harsh traffic and environmental conditions, often without any control over the way the vehicle is moving, or the driver is behaving. As a result of these specific measurement conditions, a successful implementation of a WIM system requires specific knowledge and experience.

The weight information consists of the gross vehicle weight and axle (group) loads combined with other parameters like: date and time, location, speed and vehicle class. For on-board WIM systems this pertains to the specific vehicle only. For in-road WIM systems this applies to the entire vehicle traffic flow.

This weight information provides the user with detailed knowledge of the loading of heavy goods vehicles.<ref>{{Cite news|title=Dynamic Interaction between Vehicles and Infrastructure Experiment (DIVINE project), Final Report DSTI/DOT/RTR/IR6(98)1/FINAL: OECD Scientific Expert Group IR6.|last=DEVINE|date=1998}}</ref> This information is better than with older technologies, so, for example, it is easier to match heavy goods vehicles and the road/rail infrastructure. <ref>{{Cite news|title=Vehicle mass data for pavement design and asset management. Brisbane, Australia|last=Moffatt|first=M.|date=August 2017|work=Presentation at TCA WIM Forum 2017.}}</ref>(Moffatt, 2017).

==Road applications==
[[File:Weegpunt A28.jpg|thumb|Weigh in motion location on the A28 motorway (Netherlands)]]
[[File:Aslastmeting 1995.jpg|thumb|Axle load sensor]]
Especially for [[Engineering:Truck|truck]]s, gross vehicle and axle weight monitoring is useful in an array of applications including:
* Pavement design, monitoring, and research
* [[Engineering:Bridge|Bridge]] design, monitoring, and research
* To inform weight overload enforcement policies and to directly facilitate enforcement<ref>{{Cite journal|last1=Gajda|first1=Janusz|last2=Burnos|first2=Piotr|last3=Sroka|first3=Ryszard|title=Accuracy Assessment of Weigh-in-Motion Systems for Vehicle's Direct Enforcement|url=https://ieeexplore.ieee.org/document/8263437|journal=IEEE Intelligent Transportation Systems Magazine|volume=10|issue=1|pages=88–94|doi=10.1109/MITS.2017.2776111|issn=1939-1390|date=January 2018|s2cid=31144460}}</ref><ref>{{cite journal |last1=Jacob |first1=Bernard |last2=Cottineau |first2=Louis-Marie |title=Weigh-in-motion for Direct Enforcement of Overloaded Commercial Vehicles |journal=Transportation Research Procedia |date=2016 |volume=14 |pages=1413–1422 |doi=10.1016/j.trpro.2016.05.214 |doi-access=free }}</ref>
* Planning and freight movement studies
*Toll by weight
* Data to facilitate legislation and regulation

The most common road application of WIM data is probably pavement design and assessment. In the United States, a histogram of WIM data is used for this purpose. In the absence of WIM data, default histograms are available. Pavements are damaged through a mechanistic-empirical fatigue process<ref>{{cite journal |last1=Taheri |first1=A. |last2=OBrien |first2=E. J. |last3=Collop |first3=A. C. |title=Pavement damage model incorporating vehicle dynamics and a 3D pavement surface |journal=International Journal of Pavement Engineering |date=August 2012 |volume=13 |issue=4 |pages=374–383 |doi=10.1080/10298436.2012.655741 |hdl=10197/7059 |s2cid=108816608 |hdl-access=free }}</ref> that is commonly simplified as the [[Engineering:Fourth power law|fourth power law]]. In its original form, the fourth power law states that the rate of pavement damage is proportional to axle weight raised to the fourth power. WIM data provides information on the numbers of axles in each significant weight category which allows these kinds of calculations to be carried out.{{citation needed|date=March 2019}}

Weigh in motion scales are often used to facilitate weight overload enforcement, such as the Federal Motor Carrier Safety Administration's Commercial Vehicle Information Systems and Networks program. Weigh-in-motion systems can be used as part of traditional roadside inspection stations, or as part of virtual inspection stations.<ref>{{cite web|publisher=Federal Motor Carrier Safety Administration|url=http://www.fmcsa.dot.gov/facts-research/cvisn/expanded-CVISN.htm|title=Expanded CVISN capabilities|accessdate=Feb 8, 2012}}</ref> In most countries, WIM systems are not considered sufficiently accurate for direct enforcement of overloaded vehicles but this may change in the future.<ref>{{Cite book |last1=Cornu |first1=D. |last2=Stamberg |first2=R. |last3=Kriz |first3=I. |last4=Doupal |first4=E. |year=2012 |title=One Year 'WIM Direct Enforcement' Experiences in Czech Republic |publisher=Wiley |url=https://trid.trb.org/view/1267707 |isbn=978-1-84821-415-6}}</ref>

The most common bridge application of WIM is the assessment of traffic loading. The intensity of traffic on a bridge varies greatly as some roads are much busier than others. For bridges that have deteriorated, this is important as a less heavily trafficked bridge is safer and more heavily trafficked bridges should be prioritized for maintenance and repair. A great deal of research has been carried out on the subject of traffic loading on bridges, both short-span,<ref>{{cite journal |last1=Nowak |first1=Andrzej S. |title=Live load model for highway bridges |journal=Structural Safety |date=December 1993 |volume=13 |issue=1–2 |pages=53–66 |doi=10.1016/0167-4730(93)90048-6 |hdl=2027.42/30400 |hdl-access=free }}</ref><ref>{{cite journal |last1=O'Connor |first1=Alan |last2=O'Brien |first2=Eugene J |s2cid=16871994 |title=Traffic load modelling and factors influencing the accuracy of predicted extremes |journal=Canadian Journal of Civil Engineering |date=February 2005 |volume=32 |issue=1 |pages=270–278 |doi=10.1139/l04-092 |hdl=10197/2334 |hdl-access=free }}</ref><ref>{{cite journal |last1=OBrien |first1=Eugene J. |last2=Leahy |first2=Cathal |last3=Enright |first3=Bernard |last4=Caprani |first4=Colin C. |title=Validation of scenario modelling for bridge loading |journal=The Baltic Journal of Road and Bridge Engineering |date=30 September 2016 |volume=11 |issue=3 |pages=233–241 |doi=10.3846/bjrbe.2016.27 |hdl=10197/9252 |url=https://bjrbe-journals.rtu.lv/article/view/bjrbe.2016.27 |doi-access=free |hdl-access=free }}</ref> including an allowance for dynamics,<ref>{{cite journal |last1=OBrien |first1=Eugene J. |last2=Cantero |first2=Daniel |last3=Enright |first3=Bernard |last4=González |first4=Arturo |title=Characteristic Dynamic Increment for extreme traffic loading events on short and medium span highway bridges |journal=Engineering Structures |date=December 2010 |volume=32 |issue=12 |pages=3827–3835 |doi=10.1016/j.engstruct.2010.08.018 |bibcode=2010EngSt..32.3827O |hdl=10197/4045 |s2cid=52250745 |hdl-access=free }}</ref><ref>{{cite journal |last1=Cantero |first1=Daniel |last2=González |first2=Arturo |last3=OBrien |first3=Eugene J. |s2cid=59584590 |title=Comparison of Bridge Dynamic Amplifications due to Articulated 5-Axle Trucks and Large Cranes |journal=The Baltic Journal of Road and Bridge Engineering |date=16 March 2011 |volume=6 |issue=1 |pages=39–47 |doi=10.3846/bjrbe.2011.06 |url=https://bjrbe-journals.rtu.lv/article/view/bjrbe.2011.06 |doi-access=free |hdl=10197/6217 |hdl-access=free }}</ref><ref>{{cite journal |last1=González |first1=Arturo |last2=OBrien |first2=Eugene J. |last3=Cantero |first3=Daniel |last4=Li |first4=Yingyan |last5=Dowling |first5=Jason |last6=Žnidarič |first6=Ales |title=Critical speed for the dynamics of truck events on bridges with a smooth road surface |journal=Journal of Sound and Vibration |date=May 2010 |volume=329 |issue=11 |pages=2127–2146 |doi=10.1016/j.jsv.2010.01.002 |bibcode=2010JSV...329.2127G |hdl=10197/2138 |s2cid=56078933 |hdl-access=free }}</ref> and long-span.<ref>{{cite journal |doi=10.3233/BRS-2010-006 |year=2010 |issue=1, 2 |volume=6 |author1=Nowak A.S |title=The development of live load for long span bridges |journal=Bridge Structures |author2=Lutomirska M |author3=Sheikh Ibrahim F.I |pages=73–79 }}</ref><ref>{{cite journal |last1=Micu |first1=Elena Alexandra |last2=Obrien |first2=Eugene John |last3=Malekjafarian |first3=Abdollah |last4=Quilligan |first4=Michael |title=Estimation of Extreme Load Effects on Long-Span Bridges Using Traffic Image Data |journal=The Baltic Journal of Road and Bridge Engineering |date=21 December 2018 |volume=13 |issue=4 |pages=429–446 |doi=10.7250/bjrbe.2018-13.427 |doi-access=free |hdl=10344/7494 |hdl-access=free }}</ref><ref>{{cite journal |last1=Lipari |first1=Alessandro |last2=Caprani |first2=Colin C. |last3=OBrien |first3=Eugene J. |title=A methodology for calculating congested traffic characteristic loading on long-span bridges using site-specific data |journal=Computers & Structures |date=October 2017 |volume=190 |pages=1–12 |doi=10.1016/j.compstruc.2017.04.019 }}</ref>

Recent years have seen the rise of several "specialty" Weigh-in-Motion systems. One popular example is the front fork garbage truck scale. In this application, a container is weighed—while it is full—as the driver lifts, and again—while it is empty—as the container is returned to the ground. The difference between the full and empty weights is equal to the weight of the contents.{{citation needed|date=March 2019}}

=== Use ===
Countries using Weigh in motion on highways include:

* Australia<ref>{{Cite book|title=Weigh-in-Motion Technology|year=2000 |url=https://www.pc.gov.au/inquiries/completed/freight/submissions/transport_certification_australia_/sub024attachment2.pdf|publisher=Austroads|isbn=085588553X}}</ref>
* Belgium<ref>{{Cite web|title=Weigh In Motion {{!}} Wegen en verkeer|url=https://wegenenverkeer.be/controles/vrachtvervoer/weigh-motion|access-date=2020-11-03|website=wegenenverkeer.be}}</ref><ref>{{Cite web |last= |title=Pesage dynamique |url=https://infrastructures.wallonie.be/home/nos-thematiques/routes/securite-routiere/poids-lourds/pesage-dynamique.html |access-date=2024-01-19 |website=infrastructures.wallonie.be |language=fr}}</ref>
* China<ref>{{Cite web|title=Bell tolls for expressway toll booths on provincial borders|url=http://www.ecns.cn/news/2019-12-18/detail-ifzrtayn1414083.shtml|access-date=2020-11-03|website=www.ecns.cn}}</ref><ref>{{Cite journal|last1=Hang|first1=Wen|last2=Xie|first2=Yuanchang|last3=He|first3=Jie|date=November 2013|title=Practices of using weigh-in-motion technology for truck weight regulation in China|url=https://linkinghub.elsevier.com/retrieve/pii/S0967070X13001467|journal=Transport Policy|language=en|volume=30|pages=143–152|doi=10.1016/j.tranpol.2013.09.013}}</ref>
* France<ref name=":03">{{Cite web|title=Weigh-In-Motion System Market by Type (In-Road, Bridge Weigh, Onboard), Vehicle Speed (Low, High), Component (Hardware, Software & Services), End Use Industry (Highway Toll, Oil & Refinery, Logistics), Sensors, function and Region-Global Forecast to 2026|url=https://www.marketresearch.com/MarketsandMarkets-v3719/Weigh-Motion-System-Type-Road-12387500/|access-date=2020-11-03|website=www.marketresearch.com}}</ref>
* Germany<ref name=":03" />
* Italy<ref>{{Cite web |title=Giornata di controlli del sovraccarico dei mezzi pesanti con il nuovo sistema di pesatura dinamica |url=https://www.asaps.it/66428-_bisonte_al_servizio_della_polizia_stradale.html}}</ref>
* Japan<ref>{{Cite web|title=Road Bureau - MLIT Ministry of Land, Infrastructure, Transport and Tourism|url=https://www.mlit.go.jp/road/road_e/p7_vehicle.html|access-date=2020-11-03|website=www.mlit.go.jp}}</ref>
* The Netherlands<ref>{{Cite web|title=Meer data, minder schade|url=https://www.verkeerskunde.nl/artikel/meer-data-minder-schade|access-date=2020-11-03|website=Verkeerskunde|language=nl}}</ref>
*Poland<ref>{{Cite journal|last1=Gajda|first1=Janusz|last2=Burnos|first2=Piotr|last3=Sroka|first3=Ryszard|year=2016|title=Weigh-in-Motion systems for direct enforcement in Poland|url=http://is-wim.org/icwim7/doc/icwim7_bookproceedings.pdf|journal=Proceedings of the ICWIM7: 7 International Conference on Weigh-in-Motion & PIARC workshop, Foz do Iguaçu, 2016|publisher=International Society for Weigh-In-Motion|pages=302–311}}</ref>
*Ukraine <ref>{{Cite web |title=Weigh-in-Motion Technology |url=https://ukravtodor.gov.ua/press/news/ukravtodor_prezentuvav_pershi_rezultaty_vymiriuvan_systemy_zvazhuvannia_v_rusi_wim.html}}</ref>
*United Arab Emirates <ref>{{Cite web |title=Abu Dhabi can now weigh in heavy trucks while on the move to keep roads safe |url=https://gulfnews.com/uae/abu-dhabi-can-now-weigh-in-heavy-trucks-while-on-the-move-to-keep-roads-safe-1.91270688}}</ref>
*United Kingdom<ref name=":03" />
*United States (Usage varies from state to state)<ref>{{Cite web|url=https://ops.fhwa.dot.gov/publications/fhwahop17059/index.htm|title=Virtual Weigh Stations and Weigh-in-Motion (WIM) Technology in Maryland and New York|website=FHWA|access-date=2021-10-13}}</ref>

== Accuracy ==
The accuracy of weigh-in-motion data is generally much less than for static weigh scales where the environment is better controlled. The European COST 323<ref>{{Cite web|url=https://www.cost.eu/actions/323/#tabs%7CName:overview|title=Action 323|website=COST|access-date=2019-03-14}}</ref> group developed an accuracy classification framework in the 1990s.<ref name=":1">{{Cite journal|last1=Jacob|first1=Bernard|last2=O'Brien|first2=Eugene J.|last3=Newton|first3=W.|s2cid=52574966|date=2000|title=Assessment of the accuracy and classification of weigh-in-motion systems. Part 2: European specification|journal=International Journal of Heavy Vehicle Systems|volume=7|issue=2/3|pages=153|doi=10.1504/IJHVS.2000.004831|issn=1744-232X|hdl=10197/4072|hdl-access=free}}</ref> They  also coordinated three independently controlled road tests of commercially available and prototype WIM systems, one in Switzerland,<ref>{{Cite web|url=http://wim.zag.si/reports/zurich/zurich_report.html|title=EUROPEAN CO-OPERATION EUCO-COST/323/6/97|website=wim.zag.si|access-date=2019-03-14}}</ref> one in France (Continental Motorway Test) and one in Northern Sweden (Cold Environment Test).<ref>{{Cite web|url=https://publications.europa.eu/en/publication-detail/-/publication/5eebc637-5aa6-4e5d-bd1d-01c8d13534fd|title=COST 323 : Post-proceedings of the Second European Conference on weigh-in-motion of road vehicles, Lisbon, 14th to 16th September, 1998.|last=Union|first=Publications Office of the European|date=1999-06-18|website=publications.europa.eu|access-date=2019-03-14}}</ref> Better accuracy can be achieved with multiple-sensor WIM systems<ref>{{Cite journal|last1=O'Connor|first1=Tom|last2=O'Brien|first2=Eugene J.|last3=Jacob|first3=Bernard|s2cid=56218933|date=2000|title=An experimental investigation of spatial repeatability|journal=International Journal of Heavy Vehicle Systems|volume=7|issue=1|pages=64|doi=10.1504/IJHVS.2000.004519|issn=1744-232X|hdl=10197/3985|hdl-access=free}}</ref> and careful compensation for the effects of temperature. The Federal Highway Administration in the United States has published quality assurance criteria for WIM systems<ref>{{Cite web|url=http://onlinepubs.trb.org/onlinepubs/trnews/trnews277LTPPTrafficData.pdf|title=The metamorphosis of LTPP Traffic Data|last1=Walker|first1=Debra|last2=Cebon|first2=David|year=2012|editor-last=Jacob|editor-first=Bernard|editor2-last=McDonnell|editor2-first=Anne Marie|publisher=International Society for Weigh-in-Motion|location=Dallas, Texas|editor3-last=Cunagin|editor3-first=W.}}</ref> whose data is included in the [[Engineering:Long-Term Pavement Performance|Long Term Pavement Performance]] project.

== System basics of most systems ==

=== Sensors ===
WIM systems can employ various types of sensors for measurement.

The earliest WIM systems, still used in a minority of installations, use an instrumented existing bridge as the weighing platform.<ref name=":0">{{Cite journal|last=Moses|first=Fred|date=1979|title=Weigh-in-Motion System Using Instrumented Bridges|url=https://cedb.asce.org/CEDBsearch/record.jsp?dockey=0008759|journal=Transportation Engineering Journal of ASCE|volume=105|issue=3|pages=233–249|doi=10.1061/TPEJAN.0000783}}</ref><ref name="Richardson 2014 83">{{cite journal|last1=Richardson|first1=Jim|last2=Jones|first2=Steven|last3=Brown|first3=Alan|last4=O'|first4=Eugene|last5=Brien|first5=N.A.|last6=Hajializadeh|first6=Donya|date=2014|title=On the use of bridge weigh-in-motion for overweight truck enforcement|journal=International Journal of Heavy Vehicle Systems|volume=21|issue=2|pages=83|doi=10.1504/IJHVS.2014.061632|hdl-access=free|s2cid=73594148|hdl=10197/7058}}</ref> Bending plates span a void cut into the pavement and use the flexure as the wheel passes over as a measure of weight. Load cells use strain sensors in the corner supports of a large platform embedded in the road.<ref name=":2">{{Cite journal|last1=Burnos|first1=Piotr|last2=Gajda|first2=Janusz|date=2016-12-15|title=Thermal Property Analysis of Axle Load Sensors for Weighing Vehicles in Weigh-in-Motion System|journal=Sensors|volume=16|issue=12|pages=2143|doi=10.3390/s16122143|issn=1424-8220|pmc=5191123|pmid=27983704|bibcode=2016Senso..16.2143B |doi-access=free}}</ref>

The majority of systems today are strip sensors - pressure sensitive materials installed in a 2 to 3&nbsp;cm groove cut into the road pavement. In strip sensors, various sensing materials are used, including piezo-polymer, piezo-ceramic, capacitive and piezo-quartz. Many of these sensing systems are temperature-dependent and algorithms are used to correct for this.<ref name=":2" />

Strain transducers are used in bridge WIM systems. Strain gauges are used to measure the flexure in bending plates and the deformation in load cells. The strip sensor systems use piezo-electric materials in the groove.

Capacitive systems measure the capacitance between two closely placed charged plates.<ref>{{Cite journal|last1=Cheng|first1=Lu|last2=Zhang|first2=Hongjian|last3=Li|first3=Qing|date=2007-08-17|title=Design of a Capacitive Flexible Weighing Sensor for Vehicle WIM System|journal=Sensors|volume=7|issue=8|pages=1530–1544|doi=10.3390/s7081530|issn=1424-8220|pmc=3814867|bibcode=2007Senso...7.1530C |doi-access=free}}</ref>

More recently, weighing sensors using optical fiber grating sensors have been proposed.<ref>{{Cite book|last1=Bin|first1=Ma|last2=Xinguo|first2=Zou|title=2010 International Conference on Intelligent Computation Technology and Automation |chapter=Study of Vehicle Weight-in-Motion System Based on Fiber-Optic Microbend Sensor |date=May 2010|chapter-url=http://dx.doi.org/10.1109/icicta.2010.631|pages=458–461 |publisher=IEEE|doi=10.1109/icicta.2010.631|isbn=978-1-4244-7279-6 |s2cid=15539612 }}</ref><ref>Batenko, Anatoly, et al. "Weight-in-motion (WIM) measurements by fiber optic sensor: problems and solutions." ''Transport and Telecommunication'' 12.4 (2011): 27-33.</ref><ref>{{Cite patent|number=CN103994809A|title=一种基于光纤光栅高速动态的汽车动态称重方法|gdate=2014-08-20|invent1=王强|url=https://patents.google.com/patent/CN103994809A/en?q=%22weigh+in+motion+%22&oq=%22weigh+in+motion+%22}}</ref>

=== Charge amplifiers ===
High impedance charge signals are amplified with MOSFET based charge amplifiers and converted to a voltage output, which is connected to analysis system.{{citation needed|date=March 2019}}

=== Inductive loops ===
Inductive loops define the vehicle entry and exit from the WIM station. These signals are used as triggering inputs to start and stop the measurement to initiate totaling gross vehicle weight of each vehicle. They also measure total vehicle length and help with vehicle classification. For toll gate or low speed applications, inductive loops may be replaced by other types of vehicle sensors such as light curtains, axle sensors or piezocables.{{citation needed|date=March 2019}}

=== Measurement system ===
The high speed measurement system is programmed to perform calculations of the following parameters:{{citation needed|date=March 2019}}

Axle distances, individual axle weights, gross vehicle weight, vehicle speed, distance between vehicles, and the GPS synchronized time stamp for each vehicle measurement.

The measurement system should be environmentally protected, should have a wide operating temperature range and withstand condensation.

=== Registration plate reading ===
Cameras for [[Automatic number-plate recognition|automatic number-plate recognition]] may be part of the system to check the measured weight against maximum allowable weight for the vehicle and, in case of exceeded limits, inform law enforcement in order to pursue the vehicle or to directly fine the owner.<ref>{{Cite web|title=British systems catch overloaded trucks. See how they work|url=https://trans.info/en/british-systems-catch-overloaded-trucks-see-how-they-work-108579|access-date=2020-11-03|website=Trans.INFO|language=en}}</ref>

=== Communications ===
Variety of communication methods need to be installed on the measurement system. A modem or cellular modem can be provided. In older installations or where no communication infrastructure exists, WIM systems can be self-operating while saving the data, to later physically retrieve it.{{citation needed|date=March 2019}}

=== Data archiving ===
A WIM system connected with any available communication means can be connected to a central monitoring server. Automatic data archiving software is required to retrieve the data from many remote WIM stations to be available for any further processing. A central database can be built to link many WIMs to a server for a variety of monitoring and enforcement purposes.{{citation needed|date=March 2019}}

==Rail applications==
Weighing in motion is also a common application in rail transport. 
Known applications are<ref>Buurman, Gerlof and Zoeteman, Arjen. [http://www.europeanrailwayreview.com/category/err-magazine/past-issues/issue-3-2005/page/2 "A vital instrument in asset management"], ''European Railway Review'', Issue 3, 23 August 2005.</ref>

* Asset protection (imbalances, overloading)
* Asset management 
* Maintenance planning
* Legislation and regulation
* Administration and planning

===System basics===
There are two main parts to the measurement system: the track-side component, which contains hardware for communication, power, computation, and data acquisition, and the rail-mounted component, which consists of sensors and cabling. Known sensor principles include:
* [[Physics:Strain gauge|strain gauge]]s: measuring the strain usually in the hub of the rail<ref>{{Cite web|url = http://www.unece.org/fileadmin/DAM/trans/main/temtermp/2012_2nd_Expert_Group_Meeting_Ankara/TEM_March_2012_Hbm_Argos_Ankara.pdf|title = ARGOS® – a high accurate wayside train monitoring system|date = 2012|publisher = Unece}}</ref> 
* fiber optical sensors: measuring a change of light intensity caused by the bending of the rail<ref>Gotcha Monitoring Systems [http://eurailmag.com/mag/22.htm?page=107 "Longer life for track and rollingstock"], ''=EurailMag'', Issue 22, September 2010.</ref> 
* [[Engineering:Load cell|load cell]]s: Measuring the strain change in the load cell rather than directly on the rail itself. 
* [[Physics:Laser|laser]] based systems: measuring the displacement of the rail

=== Yards and main line ===
Trains are weighed, either on the main line or at yards.{{citation needed|date=March 2019}}
Weighing in Motion systems installed on the main lines measure the complete weight (distribution) of the trains as they pass by at the designated line speed. Weighing in motion on the mainline is therefore also referred to as "coupled-in-motion weighing": all of the railcars are coupled.{{citation needed|date=March 2019}}
Weighing in motion at yards often measure individual wagons. It requires that the railcar are uncoupled on both ends in order to weigh. Weighing in motion at yards is therefore also referred to as "uncoupled-in-motion weighing". Systems installed at yards usually works at lower speeds and are capable of higher accuracies.{{citation needed|date=March 2019}}

==Airport applications==
Some airports use airplane weighing, whereby the plane taxis across the scale bed, and its weight is measured.<ref>{{Cite web|title=In Motion Aircraft Weighing Equipment - Runweight|url=https://trakblaze.com/runweight-aircraft-weighing-equipment/|access-date=2021-10-13|website=Trakblaze|language=en-US}}</ref> The weight may then be used to correlate with the pilot's log entry, to ensure there is just enough fuel, with a little margin for safety. This has been used for some time to conserve jet fuel.{{citation needed|date=March 2019}}

Also, the main difference in these platforms, which are basically a "transmission of weight" application, there are checkweighers, also known as dynamic scales or in-motion scales.{{citation needed|date=March 2019}}

== International cooperation and standards ==
The International Society for Weigh-In-Motion (ISWIM, [http://www.is-wim.net www.is-wim]) is an international non-profit organization, legally established in Switzerland in 2007. ISWIM is an international network of, and for, people and organisations active in the field of weigh-in-motion. The society brings together users, researchers, and vendors of WIM systems. This includes systems installed in or under the road pavements, bridges, rail tracks and on board vehicles. ISWIM organises periodically the international conferences on WIM (ICWIM), regional seminars and workshops as part of other international conferences and exhibitions.

In the 1990s, the first WIM standard ASTM-E1318-09<ref>{{Cite news|title=Standard Specification for Highway Weigh-in-Motion (WIM) Systems with User Requirements and Test Methods.|last=ASTM-E1318-09|date=2009|work=West Conshohocken, PA, USA: ASTM International.}}</ref> was published in North America, and the COST 323 action provided draft European specifications of WIM<ref name=":1" /> as well as reports on Pan-European tests of WIM system. The European research project WAVE <ref>{{Cite news|title=Weigh-in-Motion of Axles and Vehicles for Europe, General report.|last=WAVE|date=2002|work=LCPC, Paris, France}}</ref> and other initiatives delivered improved technologies and new methodologies of WIM. These first tests were done with the combination of WIM systems with video as a tool to assist overloading enforcement controls.<ref>{{Cite news|title=Weigh-in-Motion projects in Netherlands.|last=van Saan, H., van Loo, H.|date=2002|work=Orlando, Florida, USA, 3rd Int. Conference on Weigh-in-Motion.}}</ref>

In the early 2000s, the accuracy and reliability of WIM systems were significantly improved, and they were used more frequently for overload screening and pre-selection for road side weight enforcement controls (virtual weigh stations). The OIML R134 <ref>{{Cite news|title=Automatic instruments for weighing road vehicles in motion and measuring axle loads.|last=OIML R134|date=2009|work=International Organization for Legal Metrology, Paris, France.}}</ref> was published as an international standard of low speed WIM systems for legal applications like tolling by weight and direct weight enforcement. Most recently, the NMi-WIM standard <ref>{{Cite news|title=NMi WIM standard - Specifications and test procedures for Weigh-in-Motion Systems|last=NMi|date=2016|work=Dutch Metrology Organisation, Dordrecht, The Netherlands}}</ref> offers a basis for the introduction of high speed WIM systems for direct automatic enforcement and free flow tolling by weight.

==References==
{{Reflist}}

==External links==
* [http://www.weighinfreeflow.com 6. WEIGH-IN-FREE-FLOW]
*[http://www.invicom.com/products/weigh-in-motion.html "Weigh in Motion Systems"]
*[http://www.is-wim.org/ International Society for Weigh-In-Motion]

{{DEFAULTSORT:Weigh In Motion}}
[[Category:Road infrastructure]]
[[Category:Weighing instruments]]

{{Sourceattribution|Weigh in motion}}