## 1 Introduction  
Smart cities are receiving increasing attention from governments and society. [PERSON] et al. [1] define smart cities as \"the use of smart computing technologies to make the critical infrastructure components and services of a city--which include city administration, education, healthcare, public safety, real estate, transportation, and utilities--more inteligent\". [PERSON] and [PERSON] [2] group key conceptual components of smart cities into three categories of core factors: Technology (infrastructures of hardware and software), people (creativity, diversity, and education), and institution (governance and policy). Given the connection between the factors, a city is smart when investments in human/social capital and IT infrastructure fuel sustainable growth and enhance a quality of life, through participatory governance [3]. Over the past few decades, the growth of the urban population has been remarkable. Nowadays, 50% of the population lives in urban areas, and forecasts point that by 2050 this number will reach 70%. Today, 64% of all travel made is within urban environments and the total amount of urban kilometers traveled is expected to triple by 2050 [4]. Thus, seeking novel solutions for urban mobility becomes paramount for 21 st century society. In fact, several researches are already in advanced state: The development of autonomous vehicles [5] combined with car-sharing services [6] may shape a new automotive industry, and introduce a new paradigm in the way we use vehicles. In a few decades, cars tend to turn into services, rather than properties. Users would simply pay-per-use, instead of buying vehicles. Such change would drastically reduce the demand for parking spaces, since less vehicles would be required. At the same time, the society would benefit from a better use of natural resources employed in manufacturing vehicles (which spend a considerable part of their lifetimes parked). However, this intelligent system of urban mobility depends on the development of efficient information and communication technologies capable of providing the integration of users, vehicles, traffic lights, parking lots, traffic authorities, and all other entities involved in the traffic system [7]. Such integration can take place through, basically, three communication paradigms: (a) Cellular networks; (b) ad hoc vehicle to vehicle communication; (c) dedicated roadside infrastructure based. Most communication tends to take place through high-speed cellular networks [8; 9], ideal for commercial and third-party applications addressing real-time driver interaction [10], routes planning [11], vehicle tracking [12], monitoring driving style [13], performance of the vehicle [14], condition of roads [15; 16], driver reputation [17], network authentication [18], smart traffic lights [19], traffic monitoring [20], accident detection [21; 22], and several other types of applications still to appear in the near future. Complementary, some applications tend to benefit from the direct ad hoc communication between vehicles [23], such as collision avoidance systems [24], and platooning [25], where low communication delay, reduced risk of interference, and physical proximity are key factors. In addition to these paradigms, traffic management can also benefit from the implementation of an infrastructure-based network dedicated to vehicular communication through the deployment of communication devices in strategic locations of the road network. Such network would be responsible for routing sensitive data. Typically, these networks are managed by government, but they could also be run by private organisations, as for example through bidding. Examples of applications for these dedicated networks include traffic signal management [26], virtual traffic light implementations [27], special traffic-related communications (such as online notification of traffic penalties, lane-change maneuvers [28]), and even sending commands to vehicles (such as \"reduce speed\").