# Survey of Smart Parking Systems
###### Abstract  
The large number of vehicles constantly seeking access to congested areas in cities means that finding a public parking place is often difficult and causes problems for drivers and citizens alike. In this context, strategies that guide vehicles from one point to another, looking for the most optimal path, are needed. Most contributions in the literature are routing strategies that take into account different criteria to select the optimal route required to find a parking space. This paper aims to identify the types of smart parking systems (SPS) that are available today, as well as investigate the kinds of vehicle detection techniques (VDT) they have and the algorithms or other methods they employ, in order to analyze where the development of these systems is at today. To do this, a survey of 274 publications from January 2012 to December 2019 was conducted. The survey considered four principal features: SPS types reported in the literature, the kinds of VDT used in these SPS, the algorithms or methods they implement, and the stage of development at which they are. Based on a search and extraction of results methodology, this work was able to effectively obtain the current state of the research area. In addition, the exhaustive study of the studies analyzed allowed for a discussion to be established concerning the main difficulties, as well as the gaps and open problems detected for the SPS. The results shown in this study may provide a base for future research on the subject. s 2020 10 3872 2020 2020 2020 2020 2020 2020 2020 202  
may be complex and may involve various pieces of information which can change dynamically, for example, the driver's preferences of which streets to take, several destination points, the places for parking that are occupied while driving, the time required to get to that place, information about where the traffic lights are, information about roads that are congested or blocked, and so on. In addition, the destination can vary if the parking spot the driver is supposed to head for becomes busy while they are on their way to it which, in turn, implies that the destination point will change. All these data mean constant re-planning and updating the route from the current location of the vehicle to the desired destination is required. The algorithms can provide results that may not prove to be entirely ideal or executing them can be costly in terms of the time required for the procedure. Thus, the routing algorithm not only has to be quick enough to find the optimal path to a vacant parking place according to the needs of the driver, but also has to be adaptable to the changing environment. The current state of the art of SPS, presented in Reference [4], reviewed SPS, providing a brief description of this type of technology and classifying the systems into five main categories: parking guidance and information system, transit based information system, smart payment system, e-parking, and automated parking. The study also looks at the techniques for detecting whether a parking space is occupied or not, and how this is related to the systems previously classified. A similar article is a survey [5] that focused on exploring the concept of SPS and their categories. The survey classified the various existing parking systems and their corresponding technologies and categorized them into a summary form. Consequently, the following classification was proposed: centralized assisted parking search, non-assisted parking search, opportunistically assisted parking search, parking guidance and information system, transit based information system, smart payment system, automated parking, e-parking, car park occupancy information system, parking reservation system, intelligent transport system, intelligent parking assist system, and agent-based guiding system. [PERSON] and other authors [6] presented the results of a survey concerning drivers' parking infrastructure needs from the perspective of intelligent services.