Weigh in motion
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.
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 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.
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] 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.
[6] In most countries, WIM systems are not considered sufficiently accurate for direct enforcement of overloaded vehicles but this may change in the future.
A great deal of research has been carried out on the subject of traffic loading on bridges, both short-span,[8][9][10] including an allowance for dynamics,[11][12][13] and long-span.
The Federal Highway Administration in the United States has published quality assurance criteria for WIM systems[37] whose data is included in the Long Term Pavement Performance project.
[38][39] Bending plates span a void cut into the pavement and use the flexure as the wheel passes over as a measure of weight.
[40] The majority of systems today are strip sensors - pressure sensitive materials installed in a 2 to 3 cm groove cut into the road pavement.
Cameras for 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.
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] Some airports use airplane weighing, whereby the plane taxis across the scale bed, and its weight is measured.
These first tests were done with the combination of WIM systems with video as a tool to assist overloading enforcement controls.
[52] 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).
Most recently, the NMi-WIM standard [54] offers a basis for the introduction of high speed WIM systems for direct automatic enforcement and free flow tolling by weight.
