{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,19]],"date-time":"2025-10-19T06:07:51Z","timestamp":1760854071996,"version":"build-2065373602"},"reference-count":37,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2019,1,20]],"date-time":"2019-01-20T00:00:00Z","timestamp":1547942400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Monitoring traffic states from the road is arousing increasing concern from traffic management authorities. To complete the picture of real-time traffic states, novel data sources have been introduced and studied in the transportation community for decades. This paper explores a supplementary and novel data source, Wi-Fi signal data, to extract traffic information through a well-designed system. An IoT (Internet of Things)-based Wi-Fi signal detector consisting of a solar power module, high capacity module, and IoT functioning module was constructed to collect Wi-Fi signal data. On this basis, a filtration and mining algorithm was developed to extract traffic state information (i.e., travel time, traffic volume, and speed). In addition, to evaluate the performance of the proposed system, a practical field test was conducted through the use of the system to monitor traffic states of a major corridor in China. The comparison results with loop data indicated that traffic speed obtained from the system was consistent with that collected from loop detectors. The mean absolute percentage error reached 3.55% in the best case. Furthermore, the preliminary analysis proved the existence of the highly correlated relationship between volumes obtained from the system and from loop detectors. The evaluation confirmed the feasibility of applying Wi-Fi signal data to acquisition of traffic information, indicating that Wi-Fi signal data could be used as a supplementary data source for monitoring real-time traffic states.<\/jats:p>","DOI":"10.3390\/s19020409","type":"journal-article","created":{"date-parts":[[2019,1,22]],"date-time":"2019-01-22T03:08:22Z","timestamp":1548126502000},"page":"409","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Evaluation of a Wi-Fi Signal Based System for Freeway Traffic States Monitoring: An Exploratory Field Test"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5482-8290","authenticated-orcid":false,"given":"Fan","family":"Ding","sequence":"first","affiliation":[{"name":"Department of Civil and Environmental Engineering, University of Wisconsin, Madison, WI 53706, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8756-6960","authenticated-orcid":false,"given":"Xiaoxuan","family":"Chen","sequence":"additional","affiliation":[{"name":"Ford Motor Company, Dearborn, MI 48126, USA"}]},{"given":"Shanglu","family":"He","sequence":"additional","affiliation":[{"name":"School of Automation, Nanjing University of Science and Technology, Nanjing 210000, China"}]},{"given":"Guangming","family":"Shou","sequence":"additional","affiliation":[{"name":"School of Cyberspace Security, Southeast University, Nanjing 210000, China"}]},{"given":"Zhen","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Civil and Environmental Engineering, University of Wisconsin, Madison, WI 53706, USA"}]},{"given":"Yang","family":"Zhou","sequence":"additional","affiliation":[{"name":"Department of Civil and Environmental Engineering, University of Wisconsin, Madison, WI 53706, USA"}]}],"member":"1968","published-online":{"date-parts":[[2019,1,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"54","DOI":"10.1080\/15472451003719699","article-title":"Performance Evaluation of Travel-Time Estimation Methods for Real-Time Traffic Applications","volume":"14","author":"Ban","year":"2010","journal-title":"J. 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