The objective of this study is to evaluate the use of several warning signs and warning methods to identify those that have the greatest impact on reducing vehicle speeds when traversing a horizontal curve. Three sites were selected from a list of proposed sites for the testing of the various warning methods. Each warning treatment was installed and a five-day waiting period was allowed before operating speeds for the treatments were measured. The results of the various warning methods were mixed, however, some warning treatments were able to reduce operating speeds on a consistent basis. The most effective of these treatments were the transverse lines, the new combination Horizontal Alignment/Advisory Speed sign, and flashing lights on both the existing warning sign and new combination warning sign. It should also be noted here that for all three sites, a reduction in the average of the speeds over the 85th percentile speed was observed, indicating that most of the treatments have a reducing effect on the most unsafe driving, those traveling above the 85th percentile speed.

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The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Cabinet, nor the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names or trade names is for identification purposes only and is not to be considered an endorsement.