This appendix provides comprehensive supplementary material to support the main analysis. It includes a detailed documentation of data construction procedures, extended descriptive statistics, and additional empirical results that reinforce the robustness of the findings. Specifically, Appendix A elaborates on data processing steps and presents visualizations of the spatial distribution of roadside fuel stations, intraday pricing patterns, alternative market delineations, and spatial competition metrics. It also reports supplementary regression results from robustness and sensitivity analyses employing alternative model specifications. Appendix B presents corresponding regression estimates for Super E10 fuel, while Appendix C contains average pass-through estimates for highway service stations.