Assessing the potential of measuring IRI using smartphone technology in support of spring weight

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University of New Brunswick
Spring weight restrictions (SWR) are imposed by transportation agencies to reduce heavy vehicle loads during spring thaw when road infrastructure is most susceptible to traffic damage. Smartphone devices can be used to monitor surface roughness by converting the accelerometer output into International Roughness Index (IRI) values. This research explored the potential of using these devices to monitor IRI as an indicator of thaw-weakening potential during spring thaw to contribute to an evidence-based framework to support real-time changes to SWR. Roughness was monitored on a 1 km section of two New Brunswick highways, Route 105 (collector) and Route 616 (local), over the SWR period employed by the New Brunswick Department of Transportation and Infrastructure (NBDTI) from March 15 to May 17, 2015. Data from both locations show a similar trend in the progression of roughness, with an IRI peak within the first 2 weeks of SWR, followed by a decrease in IRI that reached baseline values 2 weeks before the end of SWR. The maximum IRI for Route 105 was 2.54 m/km (baseline 1.35 m/km) and maximum IRI for Route 616 was 6.60 m/km (baseline 3.34 m/km). In both cases, maximum IRI was approximately double baseline values. Changes in roughness observed with these devices could be associated with trigger values to initiate a protocol to respond to drastic weather changes, including focusing strength testing efforts. The results suggest weekly monitoring would be sufficient during the spring thaw, with a doubling in frequency desirable when temperatures change drastically. A framework and monitoring guidelines were developed for the inclusion of mobile roughness in the SWR decision-making process.