# Survey of Smart Parking Systems
## 6 Stage of Development  
Three states of implementation were determined for all the work analyzed. These are as follows:  
* Proposal: Work consisting of a proposal for an SPS, detection technique, algorithm, or method. * Simulated: Work that carried out laboratory simulations with the SPS proposals described in the articles, obtaining results for their evaluation. * Implemented: Work that implemented the systems described in vehicles and in public or private parking slots, and that obtained real results for this application. From the total of number articles selected, 50% (130 papers) simulated their applications, and only 2% (6 papers) really implemented them. Meanwhile, 48% (126 papers) of the publications were just a proposal for the SPS problem. In this context, we went into greater detail in the work that was implemented in reality. We analyzed the size of the parking slots where the systems were implemented, the types of VDT used, and the main strengths and weaknesses detected in each implementation. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Algorithm Implemented** & **PRS** & **PGIS** & **CAPS** & **CITS** & **AGS** & **EVPS** & **DS** & **APS** & **Total** \\ \hline Static algorithm & 32 & 5 & 2 & 13 & 0 & 5 & 7 & 11 & 75 \\ Dynamic algorithm & 10 & 21 & 15 & 16 & 5 & 5 & 4 & 10 & 86 \\ Real-time algorithm & 3 & 18 & 7 & 2 & 0 & 1 & 9 & 1 & 41 \\ No Data & 4 & 3 & 1 & 9 & 1 & 4 & 34 & 16 & 72 \\ Total & 49 & 47 & 25 & 40 & 6 & 15 & 54 & 38 & 274 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Relationship between the types of algorithms implemented (rows) and the type of SPS (columns). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Type of Algorithm** & **Number of Papers** & **References** \\ \hline \multirow{6}{*}{Static algorithms} & \multirow{6}{*}{75} & [15,16,21,23,33,42,61–64,67,68,71–75,77– \\  & & & 82,84,85,88–93,118,120,123,125,134,135, \\  & & & 155–157,159,161,162,171,173,182–185,194, \\  & & & 197,199,204,207,209,213,216,238,256,258, \\  & & & 260,261,277,279,284,288,289] \\ \hline \multirow{6}{*}{Dynamic algorithms} & \multirow{6}{*}{86} & [18–20,22,24,27–29,39–41,44–47,49–51,54, \\  & & & 55,57,60,69,83,87,97,101,103,104,106–109, \\  & & & 111,112,114,115,117,122,127–131,136,138, \\  & & & 140,141,145,147,148,150–154,158,160,164, \\  & & & 166–169,174–178,192,193,195,201,202,206, \\  & & & 247,255,259,270,274,276,280,290] \\ \hline \multirow{6}{*}{Real-time algorithms} & \multirow{6}{*}{41} & [14,26,32,34–36,38,65,66,70,100,102,110, \\  & & & 113,116,119,121,126,129,130,132,137,139, \\  & & & 142–144,146,165,166,198,205,210,211,227, \\  & & & 234,237–239,257,268,273] \\ \hline \multirow{6}{*}{No data} & \multirow{6}{*}{72} & [25,30,52,53,58,59,76,86,89,94,105,124,149, \\  & & & 163,172,179–183,186,188,191,196,198,208, \\  & & & 210,214,215,217–223,225–237,239,262–266, \\ \cline{1-1}  & & & 269,271,272,275,278,281,282,285–287] \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Number of publications per algorithms or methods applied in SPS. The first implementation corresponds to Reference [26]. In this paper, the proposed SPS was implemented in a garage containing 27 parking slots at Boston University. Each slot had sensors, but the document did not detail what the characteristics of each one were. In addition to these sensors, cameras and image processing algorithms were used to determine the status of each parking slot (empty or occupied); the joint data from the sensors and cameras were combined to increase the reliability of the estimates of parking slots. Real-time parking information was published and updated on the website and could be obtained by users. Note that the implementation was carried out in a closed parking lot, and that the occupied/unoccupied parking slots were also indicated by LED displays. The results showed that the approach improved the use of parking resources and reduced both user cost and search time. As traffic intensity increased, the improvement offered by the proposed SPS became more significant.