After successfully held for three consecutive year, 2020 4th International Conference on Traffic Engineering and Transportation System (ICTETS 2020) was successfully held during August 21-23, 2020 in Guilin, China. ICTETS 2020 is to bring together innovative academics and industrial experts in the field of traffic engineering and transportation system to a common forum. The primary goal of the conference is to promote research and developmental activities in traffic engineering and transportation system and another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world. The conference will be held every year to make it an enableing platform for people to share views and experiences in traffic engineering and transportation system and related areas.The conference featured four keynotes (40 minutes each, including Q&A) and oral presentations. The papers in the oral sessions were allotted 15 minutes each for presentation. There were a total of 110 participants, including keynote speakers, invited speaker, committee members, session chairs, authors, presenters and listeners. We are greatly honored to have invited Prof. Qizhou Hu from Nanjing University of Science and Technology, China and Prof. Dongfang Yang, from Guizhou University For Nationalities, China to serve as our General Conference Chair. The rest of the committee was composed from Turkey, Australia, India, Brazil, Malaysia, Iran and other countries.In the keynote presentations part, our beloved Conference Chair, Prof. Qizhou Hu was also invited to present his talk Thoughts on bicycle traffic in Europe. In the comprehensive analysis of the development trend of bicycle traffic in European countries, this paper analyzes the successful road of European bicycle development. In addition, we had A. Prof./Dr. Baohua Guo from Henan Polytechnic University, China to present his latest research on Rock mechanics in Road Engineering, Road safety and congestion control. The third keynote speaker. A. Prof. Shaopeng Zhong, Dalian University of Technology, China presented his latest research: Exploring the joint effect of shared autonomous vehicles and congestion pricing on regional job accessibility. On his speech, he presented shared autonomous vehicles (SAVs) and road congestion pricing studies. A. Prof./Dr. Law Teik Hua, from Road Safety Research Center, Engineering Faculty, Universiti Putra Malaysia, Malaysia, as the last keynote speaker, he presented an excellent talk: Development of safety performance index for intercity buses: An exploratory factor analysis approach. In the last part of the conference, all participants were invited to discuss and explore the academic issues after the presentations. The discussion was lasted for about 30-60 minutes. The conference provided a forum for discussing traffic engineering and transportation system and in particular for promoting the interchange of novel ideas and the presentations of the latest developments in this field. This conference will also provide an ideal environment to develop new collaborations and meet experts on the fundamentals, applications, and products of the mentioned fields.We are glad to share with you that we received lots of submissions from the conference and we selected a bunch of high-quality papers and compiled them into the proceedings after rigorously reviewed them. These papers feature following topics but are not limited to: Traffic Engineering, Transportation system and supply chain and other related topics. All the papers have been through rigorous review and process to meet the requirements of International publication standard.Lastly, we would like to express our sincere gratitude to the Chairman, the distinguished keynote speakers, as well as all the participants. We also want to thank the publisher for publishing the proceedings. May the readers could enjoy the gain some valuable knowledge from the proceedings. We are expecting more and more experts and scholars from all over the world to join this international event next year.The Organizing Committee of ICTETS 2020List of Committee member are available in the pdf.