The IFAC Symposium on Control in Transportation Systems (CTS'2021) was held in Lille from 8-10 June 2021 in a virtual form. This symposium is the 16th in the series of triennial symposia organized by the IFAC Technical Committee 7.4 on Transportation Systems. These symposia have a long tradition, starting in 1970 in Versailles, France, and continuing by taking place in several countries all over the world, with the last edition held in Savona, Italy, in 2018. This 16th symposium was organized by Université Gustave Eiffel, France. In total, 55 papers authored by 175 authors from 22 countries have been presented in the 12 regular sessions of the symposium covering numerous aspects related to the broad area of analysis, supervision, management, planning, and control of transportation systems. Besides the classic topics of this area, numerous contributions have addressed some hot topics related to artificial intelligence, connectivity and the use of formal methods for the engineering of transportation systems. The presentations of the accepted papers were made using pre-recorded videos prepared by the authors. However, Q&A sessions were scheduled after each presentation in an interactive form. Despite the fact some authors have to deal with the jet lag, almost all the corresponding authors were present during their sessions. About 120 people have joined the various symposium sessions which were very interactive with intensive interaction between the authors and the audience