# Urban Traffic Signal Control under Mixed Traffic Flows: Literature Review
## 9 Conclusions  
This paper provides an overview of the current research area state of mixed traffic flows and TSC to alleviate traffic congestion. Causing additional expenses and reducing the quality of life, urban congestion is one of the major problems for every city. Moreover, congestion even affects the development and economic growth of the cities. The available traffic data sources limit current TSC solutions. Conventional data sources cover only a section of the road in a fixed location, meaning they can provide limited information about vehicles and traffic flows. The rising popularity of CVs changes the traffic characteristics of urban areas. Many researchers explored topics of CV applications in TSC, and most of the results imply that the presence of CVs increases road capacity. Researches imply that the impact of CVs significantly depends on CVs penetration rates. CVs also affect traffic flow dynamics due to their different driving characteristics, and the results vary depending on road type. Thus, the necessary penetration rate of CVs to achieve reliable results remains an open question. New TSC strategies are complex and require high-resolution data, which CVs can provide. In that context, the availability of real-time traffic data on the microscopic level originating from CVs opens new research possibilities and enables new traffic and infrastructure management solutions. The problem of real-time processing of such data is evident and streaming data methods are a possible solution for this. One promising approach is based on STMs with the possibility of covering urban motorway and intersections traffic scenarios, especially since bottleneck locations and their intensity can be estimated with STMs. Nevertheless, more in-depth insight into the traffic network state can be gathered enabling the development of new TSC approaches using this microscopic-level data. New solutions also apply to TSC, where signal programs can have an effect on a city's traffic flow dynamics. The conceptualization of the study was conducted by [PERSON], [PERSON], [PERSON] and T.C. The funding acquisition was conducted by E.I. The writing of the original draft and preparation of the paper was conducted by [PERSON] All authors contributed to the writing of the review and final editing. The supervision was conducted by [PERSON], T.C. and [PERSON]. All authors have read and agreed to the published version of the manuscript. This work has been partly supported by the Croatian Science Foundation under the project IP-2020-02-5042 (DLASIUT), by the Science Foundation of the Faculty of Transport and Traffic Sciences under the grant Cooperative adaptive traffic signal control in mixed traffic flow environment, and by the European Regional Development Fund under the grant KK.01.1.1.01.0009 (DATACROSS). Data Availability Statement: Not applicable. This research has been carried out within the activities of the Center of Research Excellence for Data Science and Cooperative Systems supported by the Ministry of Science and Education of the Republic of Croatia. The authors declare no conflict of interest. The following abbreviations are used in this manuscript: