Effectiveness of reflectorized strips on vehicle speed and lateral placement during day and night on US 52

Run-off-road (ROR) crashes are a serious transportation issue, specially single vehicle run-off-road (SVROR) crashes on horizontal curves. Improving safety on horizontal curves helps to lower collisions numbers, prevent injuries, decrease costs, and save lives. From Federal Highway Administration (FHWA), many countermeasures have been applied to reduce crashes on curves, such as edgeline rumble strips, edgeline delineators, chevron signs, optical speed bars, and widening shoulders, etc. The purpose of this research was to assess the effectiveness of low cost measure, which is reflectorized strip, to reduce speeds and to improve lateral placement of vehicles on a horizontal curve in Iowa. A segment of US52, Sageville, Iowa, has been chosen as a study location. A before-and-after study concept was used to compare the effectiveness of a new treatment, adding reflectorized strips to the existing chevron posts. Three locations were selected for data collection spots: south point of curvature which was denote as Z1, center of curvature which was denote as Z2, and north point of curvature which was denote as Z3 on US 52. A Wilcoxon signed tank test has been used to test the median of speed and lateral placement since the data were not normally distributed. A bivariate t-test was used to find the correlation between vehicle speed and lateral placement under each treatment and lighting condition