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Based on these results, we suggest the development of educational programs focused on the following groups: child bicyclists, older bicyclists, and older drivers. Investigating and modifying street lighting could improve bicycle safety. Implementing road diets/traffic calming methods could create a safer traffic environment. Certain traffic control strategies (e.g., stop control) could be considered for uncontrolled intersections with high bicycle exposure, and helmet campaigns should be launched to increase helmet awareness and use. The study also suggests some interesting future research directions, including examining driver/bicyclist behaviors at uncontrolled intersections and studying the riding behaviors of child bicyclists in Kentucky.

This work mainly investigated the microstructure and mechanical properties of Mg-Zn-Y-Zr alloys with Zn/Y ratios of 5 and 10. An X-ray diffraction (XRD) analysis indicated that the two alloys were mainly composed of an icosahedral phase (I-phase) and a-Mg matrix. For the alloy with a Zn/Y ratio of 10, however, the diffraction peaks of the I-phase were stronger. Microstructure observation showed that the I-phase preferentially existed in the form of I-phase/a-Mg matrix interdendritic eutectic pockets at grain boundaries. Moreover, when the Zn/Y ratio was increased 2 times, the volume fraction of the I-phase in the a-Mg matrix increased 1.5 times and a tiny Mg 7 Zn 3 phase formed. Energy-dispersive spectroscopy (EDS) mapping and electron probe microanalysis (EPMA) results suggested that the chemical composition of the I-phase was not a constant value. Computer-aided cooling curve analysis (CA-CCA) indicated that, for the alloy with a Zn/Y ratio of 5, formation of the I-phase relied on the W-phase transformation and the eutectic reaction of the residual melt. However, the I-phase formation for the alloy with a Zn/Y ratio of 10 depended on the eutectic reaction of the melt. Tensile tests indicated that the mechanical properties of the two as-cast alloys were poor. After hot extrusion processing, the mechanical properties of the alloy with a Zn/Y ratio of 10 were noticeably increased. The ultimate tensile strength (UTS) and elongation to failure reached 320 MPa and 13 pct, respectively.

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