Description: Horizontal curves (H-curves) are the road segments greatly change the alignment or direction of roadways, which have been reported to be critical for traffic safety (FHWA 2016). Since quantitative characteristics (e.g., curvature, length, turning angle) are inevitable for in-depth modeling and evaluating H-curve safety, gathering H-curve data from existing road network is needed. As such, the research team at Old Dominion University (ODU) has worked with the Virginia Department of Transportation (VDOT) to develop a more efficient H-curve data collection solution. Specifically, the research team has developed a web-based tool that can identify and extract H-curves automatically from existing roadway shapefiles. This tool has been adopted to facilitate VDOT collecting statewide H-curve data with detailed quantitative attributes. The collected curve data can be also conflated with existing VDOT LRS system. This tutorial document introduces the development of the tool and data processing for obtaining the final datasets.