Rural Data Collection Technology - FHWA Operations - U.S. ...

Figure 5Typical Sensys implementation showing sensor array,repeater, and access pointSource: www.sensysnetworks.commagnetometers are not likely to be practical forshort-term deployments.Additional data such as vehicle class data can alsobe derived from this technology, though additionalsensors may be required in an array. Research byMedina, Hajbabaie, and Benekohal (2010) cautionsthat magnetic detectors may overcount vehicles ator near signalized intersections by 16 to 22 percent,largely due to detections of vehicles in adjacentlanes or vehicles positioned between lanes. Day,Premachandra, Brennan, Sturdevant, and Bullock(2009) also found that magnetic detectors may missdetections of motorcycles if the motorcycle does notpass directly over the detector. Although installed inpavement, Sensys sensors can perform diagnosticchecks and software upgrades remotely. Devices canbe removed from pavement and reused.CostsCosts for in-pavement magnetic detectors dependupon a number of factors, including number ofsensors per array and the number of arrays perlocation (i.e., number of lanes monitored). Costs mayalso vary depending upon other services providedby the technology vendor. Although in-pavementmagnetic detection is likely to cost significantly morethan Bluetooth detection, the devices are expected torequire little to no maintenance during their reported10 year battery life. However, road work may requirethe devices to be removed before the end of theirbattery life.Privacy IssuesBecause magnetic detectors rely on a vehicle’smagnetic signature, which can change dependingupon vehicle occupancy and other factors, they offera very high degree of inherent motorist privacy. Ananonymous identifier is assigned to a vehicle thatallows it to be re-identified at a downstream location.Future ConsiderationsThere are no emerging trends that are expected toinfluence the use of in-pavement magnetic detection.It is a viable solution for RTT data collection, as longas communications are available, and is expected toremain so.Rural Data Collection TechnologyFederal Highway Administration13