{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,11]],"date-time":"2026-07-11T05:23:19Z","timestamp":1783747399796,"version":"3.55.0"},"reference-count":46,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2015,12,16]],"date-time":"2015-12-16T00:00:00Z","timestamp":1450224000000},"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>Wireless technologies are making the development of new applications and services in vehicular environments possible since they enable mobile communication between vehicles (V2V), as well as communication between vehicles and infrastructure nodes (V2I). Usually, V2V communications are dedicated to the transmission of small messages mainly focused on improving traffic safety. Instead, V2I communications allow users to access the Internet and benefit from higher level applications. The combination of both V2V and V2I, known as V2X communications, can increase the benefits even further, thereby making intelligent transportation systems (ITS) a reality. In this paper, we introduce V2X-d, a novel architecture specially designed to estimate traffic density on the road. In particular, V2X-d exploits the combination of V2V and V2I communications. Our approach is based on the information gathered by sensors (i.e., vehicles and road side units (RSUs)) and the characteristics of the roadmap topology to accurately make an estimation of the instant vehicle density. The combination of both mechanisms improves the accuracy and coverage area of the data gathered, while increasing the robustness and fault tolerance of the overall approach, e.g., using the information offered by V2V communications to provide additional density information in areas where RSUs are scarce or malfunctioning. By using our collaborative sensing scheme, future ITS solutions will be able to establish adequate dissemination protocols or to apply more efficient traffic congestion reduction policies, since they will be aware of the instantaneous density of vehicles.<\/jats:p>","DOI":"10.3390\/s151229889","type":"journal-article","created":{"date-parts":[[2015,12,16]],"date-time":"2015-12-16T10:11:27Z","timestamp":1450260687000},"page":"31794-31810","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":51,"title":["Sensing Traffic Density Combining V2V and V2I Wireless Communications"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0688-3751","authenticated-orcid":false,"given":"Julio","family":"Sanguesa","sequence":"first","affiliation":[{"name":"DIIS, University of Zaragoza, Ciudad Escolar s\/n, Teruel 44003, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Javier","family":"Barrachina","sequence":"additional","affiliation":[{"name":"DIIS, University of Zaragoza, Ciudad Escolar s\/n, Teruel 44003, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manuel","family":"Fogue","sequence":"additional","affiliation":[{"name":"DIIS, University of Zaragoza, Ciudad Escolar s\/n, Teruel 44003, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Piedad","family":"Garrido","sequence":"additional","affiliation":[{"name":"DIIS, University of Zaragoza, Ciudad Escolar s\/n, Teruel 44003, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6945-7330","authenticated-orcid":false,"given":"Francisco","family":"Martinez","sequence":"additional","affiliation":[{"name":"DIIS, University of Zaragoza, Ciudad Escolar s\/n, Teruel 44003, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0038-0539","authenticated-orcid":false,"given":"Juan-Carlos","family":"Cano","sequence":"additional","affiliation":[{"name":"DISCA, Universitat Polit\u00e8cnica de Val\u00e8ncia, Camino de Vera s\/n, Valencia 46022, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5729-3041","authenticated-orcid":false,"given":"Carlos","family":"Calafate","sequence":"additional","affiliation":[{"name":"DISCA, Universitat Polit\u00e8cnica de Val\u00e8ncia, Camino de Vera s\/n, Valencia 46022, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3753-0403","authenticated-orcid":false,"given":"Pietro","family":"Manzoni","sequence":"additional","affiliation":[{"name":"DISCA, Universitat Polit\u00e8cnica de Val\u00e8ncia, Camino de Vera s\/n, Valencia 46022, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2015,12,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1016\/j.trc.2015.03.041","article-title":"Vehicular ad-hoc networks sampling protocols for traffic monitoring and incident detection in Intelligent Transportation Systems","volume":"56","author":"Baiocchi","year":"2015","journal-title":"Transp. Res. Part C Emerg. Technol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1156","DOI":"10.1109\/TITS.2012.2190509","article-title":"Vehicular Traffic Density State Estimation Based on Cumulative Road Acoustics","volume":"13","author":"Tyagi","year":"2012","journal-title":"IEEE Trans. Intell. Transp. Syst."},{"key":"ref_3","first-page":"153","article-title":"Cooperation as a service in VANET: Implementation and simulation results","volume":"8","author":"Mousannif","year":"2012","journal-title":"Mob. Inf. Syst."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.trc.2014.05.006","article-title":"Experimental evaluation of CAM and DENM messaging services in vehicular communications","volume":"46","author":"Santa","year":"2014","journal-title":"Transp. Res. Part C Emerg. Technol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1007\/s11235-010-9325-z","article-title":"Traffic differentiation support in vehicular delay-tolerant networks","volume":"48","author":"Soares","year":"2011","journal-title":"Telecommun. Syst."},{"key":"ref_6","first-page":"1728","article-title":"An on Demand Interference Aware Routing Protocol for VANETS","volume":"7","author":"Fazio","year":"2012","journal-title":"J. Netw."},{"key":"ref_7","first-page":"213","article-title":"Implementation of CAVENET and its usage for performance evaluation of AODV, OLSR and DYMO protocols in vehicular networks","volume":"6","author":"Spaho","year":"2010","journal-title":"Mob. Inf. Syst."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"158","DOI":"10.1504\/IJIPT.2009.028655","article-title":"Assessment of VANET multi-hop routing over an experimental platform","volume":"4","author":"Santa","year":"2009","journal-title":"Int. J. Internet Protoc. Technol."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Suwannasa, A., Puangpronpitag, S., and Phongsiri, W. (2013). A novel authentication scheme for V2I communication based on WAVE unicast services. Int. J. Distrib. Sens. Netw., 2013.","DOI":"10.1155\/2013\/827084"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"831","DOI":"10.1007\/s11036-013-0473-8","article-title":"VSPLIT: A cross-layer architecture for V2I TCP services over 802.11","volume":"18","author":"Rene","year":"2013","journal-title":"Mob. Netw. Appl."},{"key":"ref_11","first-page":"69","article-title":"Sharing with caution: Managing parking spaces in vehicular networks","volume":"9","author":"Delot","year":"2013","journal-title":"Mob. Inf. Syst."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1155\/2014\/629412","article-title":"Intelligent advisory speed limit dedication in highway using VANET","volume":"2014","author":"Jalooli","year":"2014","journal-title":"Sci. World J."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Du, S., Tian, P., Ota, K., and Zhu, H. (2013). A secure and efficient data aggregation framework in vehicular sensing networks. Int. J. Distrib. Sens. Netw., 2013.","DOI":"10.1155\/2013\/298059"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Zhu, X., Lu, Y., Zhang, B., and Hou, Z. (2013). A distributed pseudonym management scheme in VANETs. Int. J. Distrib. Sens. Netw., 2013.","DOI":"10.1155\/2013\/615906"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"318","DOI":"10.1007\/s11036-013-0446-y","article-title":"RCare: Extending secure health care to rural area using VANETs","volume":"19","author":"Barua","year":"2014","journal-title":"Mob. Netw. Appl."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Chen, P.Y., Liu, J.W., and Chen, W.T. (2010, January 6\u20139). A Fuel-Saving and Pollution-Reducing Dynamic Taxi-Sharing Protocol in VANETs. Proceedings of the IEEE 72nd Vehicular Technology Conference Fall (VTC 2010-Fall), Ottawa, ON, Canada.","DOI":"10.1109\/VETECF.2010.5594422"},{"key":"ref_17","first-page":"259","article-title":"Robust video communication over an urban VANET","volume":"6","author":"Qadri","year":"2010","journal-title":"Mob. Inf. Syst."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1377","DOI":"10.1109\/TMC.2012.115","article-title":"Optimal Content Downloading in Vehicular Networks","volume":"12","author":"Malandrino","year":"2013","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"90","DOI":"10.1109\/MVT.2012.2203877","article-title":"Automatic Accident Detection: Assistance Through Communication Technologies and Vehicles","volume":"7","author":"Fogue","year":"2012","journal-title":"IEEE Veh. Technol. Mag."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1016\/j.trc.2009.05.007","article-title":"An analysis of communication and navigation issues in collision avoidance support systems","volume":"18","author":"Santa","year":"2010","journal-title":"Transp. Res. Part C Emerg. Technol."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Maslekar, N., Boussedjra, M., Mouzna, J., and Labiod, H. (2011, January 4\u20138). A stable clustering algorithm for efficiency applications in VANETs. Proceedings of the 7th International Wireless Communications and Mobile Computing Conference (IWCMC), Istanbul, Turkey.","DOI":"10.1109\/IWCMC.2011.5982709"},{"key":"ref_22","unstructured":"Tan, E., and Chen, J. (2007, January 5\u20137). Vehicular Traffic Density Estimation via Statistical Methods with Automated State Learning. Proceedings of the IEEE Conference on Advanced Video and Signal Based Surveillance (AVSS), London, UK."},{"key":"ref_23","unstructured":"Coifman, B., and Lee, H. (October, January 30). Analytical Tools for Loop Detectors and Traffic Monitoring Systems. Proceedings of the IEEE Intelligent Transportation Systems Conference (ITSC), Seattle, WA, USA."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Stanica, R., Chaput, E., and Beylot, A. (2011, January 11\u201314). Local density estimation for contention window adaptation in vehicular networks. Proceedings of the IEEE 22nd International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), Toronto, ON, Canada.","DOI":"10.1109\/PIMRC.2011.6140062"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2399","DOI":"10.3390\/s130202399","article-title":"An Infrastructureless Approach to Estimate Vehicular Density in Urban Environments","volume":"13","author":"Sanguesa","year":"2013","journal-title":"Sensors"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Ancona, S., Stanica, R., and Fiore, M. (2014, January 2\u20134). Performance Boundaries of Massive Floating Car Data Offloading. Proceedings of the 11th Annual Conference on Wireless on-Demand Network Systems and Services (WONS), Obergurgl, Austria.","DOI":"10.1109\/WONS.2014.6814727"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"De Fabritiis, C., Ragona, R., and Valenti, G. (2008, January 12\u201315). Traffic Estimation and Prediction Based on Real Time Floating Car Data. Proceedings of the 11th International IEEE Conference on Intelligent Transportation Systems (ITSC), Beijing, China.","DOI":"10.1109\/ITSC.2008.4732534"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Rashidi, M., Batros, I., Madsen, T., Riaz, M., and Paulin, T. (2012, January 3\u20135). Placement of Road Side Units for Floating Car Data Collection in Highway Scenario. Proceedings of the 4th International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT), St. Petersburg, Russia.","DOI":"10.1109\/ICUMT.2012.6459649"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Torres, A., Ji, Y., Calafate, C., Cano, J.C., and Manzoni, P. (2014, January 2\u20134). V2X solutions for real-time video collection. Proceedings of the IEEE\/IFIP 11th Annual Conference on Wireless on-Demand Network Systems and Services (WONS), Obergurgl, Austria.","DOI":"10.1109\/WONS.2014.6814731"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Knapik, P., Schoch, E., and Kargl, F. (2013, January 2\u20135). Electronic decal: A security function based on V2X communication. Proceedings of the IEEE Vehicular Technology Conference, Dresden, Germany.","DOI":"10.1109\/VTCSpring.2013.6692534"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Miller, J. (2008, January 4\u20136). Vehicle-to-vehicle-to-infrastructure (V2V2I) intelligent transportation system architecture. Proceedings of the IEEE Intelligent Vehicles Symposium, Eindhoven, the Netherlands.","DOI":"10.1109\/IVS.2008.4621301"},{"key":"ref_32","unstructured":"Lassiter, E. (1975, January 12\u201314). Navstar Global Positioning System: A Satellite Based Microwave Navigation System. Proceedings of the IEEE-MTT-S International Microwave Symposium, Palo Alton, CA, USA."},{"key":"ref_33","unstructured":"Prasad, R., and Ruggieri, M. (2005). Applied Satellite Navigation Using GPS, GALILEO, and Augmentation Systems, Artech Hous."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1109\/MITS.2013.2253159","article-title":"Road Side Unit Deployment: A Density-Based Approach","volume":"5","author":"Barrachina","year":"2013","journal-title":"IEEE Intell. Transp. Syst. Mag."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"708","DOI":"10.1109\/LCOMM.2014.022514.140206","article-title":"Performance Evaluation of IEEE 802.11p-Enabled Vehicular Video Surveillance System","volume":"18","author":"Bellalta","year":"2014","journal-title":"IEEE Commun. Lett."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1023\/A:1013763825347","article-title":"The Broadcast Storm Problem in a Mobile Ad Hoc Network","volume":"8","author":"Tseng","year":"2002","journal-title":"Wirel. Netw."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.trc.2014.02.010","article-title":"Using topology and neighbor information to overcome adverse vehicle density conditions","volume":"42","author":"Sanguesa","year":"2014","journal-title":"Transp. Res. Part C Emerg. Technol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1206","DOI":"10.1016\/j.eswa.2013.08.004","article-title":"Reducing emergency services arrival time by using vehicular communications and Evolution Strategies","volume":"41","author":"Barrachina","year":"2014","journal-title":"Expert Syst. Appl."},{"key":"ref_39","unstructured":"ZunZun Online Curve Fitting and Surface Fitting Web Site, 2015. Available online:http:\/\/www.zunzunhelp.com\/."},{"key":"ref_40","unstructured":"Fall, K., and Varadhan, K. ns Notes and Documents. The VINT Project. UC Berkeley, LBL, USC\/ISI, and Xerox PARC, 2000. Available online:http:\/\/www.isi.edu\/nsnam\/ns\/ns-documentation.html."},{"key":"ref_41","unstructured":"Grupo de Redes de Computadores Software Developed by Members of the Research Group, 2015. Available online:http:\/\/www.grc.upv.es\/software\/."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Jiang, D., Chen, Q., and Delgrossi, L. (2008, January 14\u201319). Optimal Data Rate Selection for Vehicle Safety Communications. Proceedings of the Fifth ACM International Workshop on VehiculAr Inter-NETworking, San Francisco, CA, USA.","DOI":"10.1145\/1410043.1410050"},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Fogue, M., Garrido, P., Martinez, F.J., Cano, J.C., Calafate, C.T., and Manzoni, P. (2012, January 19\u201323). A Realistic Simulation Framework for Vehicular Networks. Proceedings of the 5th International ICST Conference on Simulation Tools and Techniques (SIMUTools 2012), Desenzano, Italy.","DOI":"10.4108\/icst.simutools.2012.247682"},{"key":"ref_44","unstructured":"OpenStreetMap Collaborative Project to Create a Free Editable Map of the World, 2015. Available online:http:\/\/www.openstreetmap.org."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"639","DOI":"10.1007\/s11277-012-0594-6","article-title":"Computer Simulations of VANETs Using Realistic City Topologies","volume":"69","author":"Martinez","year":"2013","journal-title":"Wirel. Pers. Commun."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"5597","DOI":"10.1103\/PhysRevE.55.5597","article-title":"Metastable states in a microscopic model of traffic flow","volume":"55","author":"Krauss","year":"1997","journal-title":"Phys. Rev. E"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/12\/29889\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T20:54:10Z","timestamp":1760216050000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/12\/29889"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,12,16]]},"references-count":46,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2015,12]]}},"alternative-id":["s151229889"],"URL":"https:\/\/doi.org\/10.3390\/s151229889","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2015,12,16]]}}}