Urban air pollution has become a major concern for numerous densely populated cities globally since poor air quality may cause various health problems. The first crucial step towards solving this important problem is to identify the most critical areas with the highest air pollution over the allowed limit. Nowadays, air pollution is monitored by various stationary measurement systems that are expensive, large, consume a big amount of energy and gathered data has a low spatial resolution. This

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... per presents EnvioDev, a mobile air quality and traffic conditions measurement device for Vehicular Ad hoc Networks (VANETs) that can be used on any type of a vehicle. EnvioDev was tested in a real-world urban environment measuring CO, CH 4 and LPG concentrations, as well as air temperature and humidity in order to create a city pollution map and the results are presented in the paper. Moreover, in order to determine how many EnvioDev devices are required to obtain close to a realtime air quality map of an urban area, three experiments with Simulation of Urban Mobility (SUMO) simulator were conducted. In the experiments an urban city map was divided into five zones and data aggregation frequencies are varied during different traffic load periods in order to study the number of required vehicles with EnvioDev measurement device. The obtained results show that by increasing the data aggregation frequency the number of required vehicles with EnvioDev measurement device increases and it is depended on the size and topology of the testing area. using GPS sensor. Finally, all obtained data is transmitted to online cloud by using a GSM module. B. Network and Communication Structure Communication and network structure are designed to provide efficient data collection, interpretation, processing and cloud storage. The sensors use I2C, a half-duplex communication protocol, and SPI, a full duplex commination protocol, to send data to the Arduino microcontroller. After receiving data from sensors, Arduino interprets and formats the data which is then sent to the GSM module. The GSM module supports bidirectional communication and is used to send data to the software system in the cloud where they will be processed, stored and used to create a pollution map of the target area. The goal is to provide proactive and reactive communication and data delivery with the lowest possible latency. In that regard the 4G mobile network used in the experiments showed satisfying performances. Fig. 2 shows EnvioDev communication and network structure. Communication capabilities of EnvioDev can be extended by using Dedicated Short Range Communication (DSRC) technology specifically designed for VANETs with V2V or V2I communication models [15] or Internet of Things (IoT) technology that is emerging in VANETs recently [16].