# Survey of Smart Parking Systems
## 7 Discussion and Open Problems
### Inclusion of SPS in Smart Cities  
The IoT is a multidisciplinary concept that allows the deployment of an infrastructure that can be developed in a large number of areas. It can be applied to data processing methods, security systems, accessibility, and even social and industry applications, enabling real-world interaction with computers that interact with the environment by processing sensory data and permitting the acquisition of skills that help improve people's quality of life [309]. One of the many uses of this infrastructure is for smart cities.  
Smart cities use IoT by employing sensors, alarms, actuators, and other devices to collect and analyze data, assist in making decisions, trigger events, and even control the environment [219].  
In recent years, this concept took hold, and IoT developments for smart cities multiplied in several areas of some cities. SPS can be considered one of the first successful implementations.  
Cities like Santander [204] or Barcelona [310] in Spain, or San Francisco [295] in the USA managed to implement SPS, and they were able to obtain excellent results that demonstrate that this type of system can be part of (and even one of the most important applications in) a smart city ecosystem.  
The future of smart cities is clearly growing, such that many cities can adopt an SPS that solves the problem of parking a vehicle for its citizens. However, these implementations have to be context-sensitive. All cities have different infrastructures, different investment budgets, and different societies. There are cities where parking slots are arranged along the same roads where cars circulate, while others have developed public or semi-public parking slots in buildings or off-road areas,while others combine these two options. These different contexts mean that the implementation of a type of SPS (see Table 5) must be carried out on an almost custom-made basis for each city, and the choice of SPS type may vary according to how best to solve the parking problem and by taking into account the aforementioned aspects.  
Cities with limited budgets can choose to develop a CITS type of SPS, implementing a crowdsourcing application and encouraging its use among their citizens, while others with a larger infrastructure can deploy sensors throughout the city to provide accurate information on the status of parking slots.  
Large cities that use public parking slots on the streets can offer greater benefits to drivers if they implement a PGIS, providing route guidance to the parking location chosen by the application or user, while others that offer solutions such as parking slots in buildings can combine PGIS to guide drivers to some of them, as well as a CAPS to report on the status of the parking slots in each location, thus allowing users to choose which one they want.  
As discussed in this section, cities that have a parking control system with inspector-controlled operators or parking meters can invest in providing an SPS using the data they process every day by these means. As we can conclude, SPS adaptation in cities can be diverse, and the choice of which type of system to implement will depend on the reality of each individual city. What is clear is that solving the parking problem can foster the growth of smart cities.