Highlights • Evaluation of a system warning cyclists against safety critical events trimodally. • Cyclist warning system using real time information provided by connected traffic. • Earlier braking reactions for rides with vs. without warning system. • System can enhance cyclists’ situation awareness in safety critical situations. • Increased perceived safety and stable workload for rides with vs. without system.

Abstract Problem: Increasing numbers of crashes involving pedelecs, and particularly older pedelec users, induce a need to enhance cycling safety. We evaluated a prototype cyclist warning system (CWS) that aims to increase situation awareness (SA) by alerting to safety critical events (SCE) with trimodal (auditory, visual, tactile). Method: To investigate the effects of CWS usage, we conducted a 2x2 mixed design bicycle simulator study with factors (1) CWS usage (within: rides WITH vs. WITHOUT CWS) and (2) age group (between: younger vs. older cyclists) on braking reaction time, gaze behavior, mental workload, and perceived safety. In sum, N = 64 participants (n = 32 younger, 18–40 years; n = 32 older, ≥ 55 years) took part in the study and experienced two balanced blocks of short rides including SCE of particular relevance for cycling safety. Results: CWS usage resulted in earlier braking reactions to all investigated SCE and partly earlier fixation on the critical interaction partners (CIP) indicating increased cyclists’ SA. Consistently to behavioral measures, participants’ assessments regarding perceived safety further supported the safety improvements derived from CWS independently of age group. Moreover, CWS usage did not add to mental workload ratings. Age effects were selectively found for gaze data showing that across all SCE, older adults fixated longer and more frequently on street alignment, and less frequently on other road users. Discussion: Taken together, the CWS evaluation showed promising results indicating the potential of the tested CWS to increase SA and enhance cyclists’ safety both on a behavioral level and regarding subjective assessments. Further research should address the systems’ safety potential under real-world conditions and for situations of higher complexity. Practical Applications: Understanding the potential impact of road safety measures such as CWS is important to contribute effectively to reducing SCE.