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Iowa State University--Becoming the Best

Horizontal Curve Identification and Evaluation


Principal investigators:

Co-principal investigators:

Project status


Start date: 01/01/10
End date: 12/31/10


Report: Horizontal Curve Identification and Evaluation (897.88 kb pdf) September 2012


Sponsor(s): Iowa Department of Transportation

About the research


Horizontal curves are over-represented, high-frequency, high-severity crash locations. Significant opportunities exist to mitigate these crashes through relatively low-cost safety improvements such as paved shoulders, rumble strips/stripes, and improved signing and delineation.

However, the presence of horizontal curvature is not captured as part of the Iowa crash report and the Iowa Department of Transportation (DOT)-maintained database of public roadways does not identify the locations of horizontal curvature. Therefore, it is currently difficult to identify the locations of curves systematically, and particularly high-crash curves and the characteristics of these curves.

The goal of this project was to expand the Iowa Department of Transportation (DOT) effort to systematically identify high-crash and potentially-problematic horizontal curves.

The primary objective of this project was to refine the previously-developed, preliminary, horizontal-curve database, allowing specific curve parameters to be extracted and evaluated system wide. This refinement facilitates identification of not only high-crash locations but candidate sites for low-cost safety improvements.

Secondary objectives include updating the high-crash curve list, evaluating the accuracy of the geometric parameter estimates and testing the sensitivity of safety performance to errors in curve parameters.