A review of state-of-the-art bicycle technologies affecting cycling safety: level of smartness and technology readiness

New technologies are gaining ground in various disciplines, and road safety is not an exception. The objective of this paper is twofold: (1) to review the state-of-the-art technologies implemented in bicycles to improve cyclists' safety, and (2) to propose a classification for the levels of smartness of emerging "smart bikes". This paper defines six levels of smartness for bicycles based on their functionality and evaluates the Technology Readiness Levels of bicycle technologies. Furthermore, areas for future research were identified and discussed. To achieve these, we conducted a literature review which employed two academic databases -Scopus and Web of Science- and the Google Scholar search engine, following the framework of the systematic literature review methodology for the search and selection process. A total of 36 studies that met the inclusion criteria were investigated. The majority of these studies focus on warning systems aiming to forestall an imminent collision, mostly by using accelerometers/gyroscopes, LIDAR, sensors and networking communication. These systems, despite their preliminary state, demonstrate a positive effect on cyclists' safety. The review concludes that there is a need for further deployment and testing of such systems with field trials to gain concrete evidence regarding their impact on cyclists' safety. It also highlights that advanced technologies are scarcely implemented in bicycles and that most smart bicycle systems are based on smartphones. Thus, the question is: what lies in the future of smart bicycles from today's perspective?