Contactless Bridge Weigh-in-Motion (cBWiM)

T. Ohio, C. H. Carey, E. J. OBrien, C. Doherty, S. E. Taylor

Research output: Contribution to journalArticlepeer-review

109 Citations (Scopus)


Bridge weigh-in-motion (WIM) uses existing bridges to find the weights of vehicles that pass overhead. Contactless bridge weigh-in-motion (cBWIM) uses bridges to weigh vehicles without the need for any sensors to be attached to the bridge. A camera is mounted on the back of a telescope, which magnifies the image to the extent that sub millimeter bridge deflections can be measured accurately. A second camera is used to monitor traffic and to determine axle spacings. The two cameras are synchronized using light-emitting diodes (LEDs) activated by an interval timer. The exact position of the test vehicle relative to the bridge influence line is determined by optimization at a post processing stage. The new WIM concept was tested on a bridge in the United Kingdom. In a modest test sample of eight statically weighed vehicles, cBWIM was shown to be a feasible alternative to other forms of WIM. Accuracy of gross weight is already reasonably good; accuracy of groups and individual axles will require greater magnification or additional cameras.
Original languageEnglish
Number of pages10
JournalJournal of Bridge Engineering
Issue number7
Early online date08 Feb 2016
Publication statusPublished - Jul 2016


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