Nationwide Horizontal Curve Inventory

Horizontal curves are indispensable for roadway safety and mobility. Public transportation agencies are exploring efficient and effective approaches to better understand the spatial location, geometrical attributes and conditions of the horizontal curves within their extensive networks of road jurisdiction. With the wide availability of global positioning system (GPS) and geographic information system (GIS) data, some efforts have been made to develop automated algorithms for identifying horizontal curves from GPS trajectories or GIS basemaps. While these methods have shown promising results, they have not been validated or practically applied over large testing datasets with complicated road network connections.

In this study, the research team will continuously process the networks nationwide using the publicly available GIS basemaps, to cover more than 150,000 miles of the United States Numbered Highway system.  This gallery of horizontal curve inventories shows the current availability of the results. Please click the link underneath the map for more information.

Definition – The curve inventory results will include all the properties that are necessary for safety analysis or other applications. Depending on different basemap formats, the curve inventory will at least include the following attributes and represented based on the corresponding linear reference system. 

Citation – If the results and the datasets are used for academic publication, please appropriately cite the basemap data source (as listed in the corresponding result section) and the following paper in the publication.

Ai, C. and Tsai, Y. (2015). ”Automatic Horizontal Curve Identification and Measurement Method Using GPS Data.” ASCE Journal of Transportation Engineering, 141(2), 04014078

Ai, C. and Qiu, S. (2019). “Development of A Nationwide Horizontal Curve Inventory Using Open GIS Data.” International Conference on Transportation & Development 2019, Alexandria, VA.

Disclaimer – All the results and information for the horizontal curves on this website were derived ONLY for academic research purposes. The Ai Research Group derived the results based on the publicly available data at the time of processing, but it does not guarantee any changes in the data sharing policy of the hosting agencies. Please contact the data hosting agencies for more information. The copyright of the data belongs to the data hosting source as the copyright text indicates. The Ai Research Group has internally evaluated and validated the results before it releases any results on this website, but it does not guarantee the quality and the accuracy of the results, nor imply any of its potential applications. Please use the data and the results at your risk, and please use the data ONLY for academic purposes.