Vulnerable Road Users (VRUs) are moving into the focus of road safety solutions, be it Advanced Driver Assistance Systems (ADAS) deployed in cars or enhanced guidance systems in smart cities. We concentrate on bicyclists and study means for assessing the impact of such safety solutions on the bicyclistsŠ behavior. We just recently developed the Virtual Cycling Environment (VCE), which allows a bicyclist to ride in a virtual reality environment while sitting on a real bike connected with a simulated environment. In this paper, we present a method for measuring the cyclistsŠ visual attention. This is a fundamental requirement for advanced studies of VRU safety systems including their performance as well as acceptance. In a small empirical study, we assess the feasibility of our approach for conducting psychological experiments in a human-in-the-loop setup.