Further Considerations for Effective Median Barrier Lateral Placement for Varying Highway Cross Sections

The primary purpose of longitudinal median barriers is to redirect errant vehicles that depart the roadway and thus prevent collisions with opposing traffic, terrain features, or roadside objects, which could lead to severe impacts. In the study reported in this paper, vehicle dynamics analysis was used to identify the influences of varying median configurations on interface effectiveness of barrier lateral placement options. The same approach taken in previous efforts to consider five vehicle types for a range of impact conditions was taken here, except that only uniform median configurations were considered. The variations in median shape, side slopes, and roadway elevations in the analyses were reflected in nonsymmetrical override and underride limits. Data for a road section under consideration for median improvement provided the basis for the assessment of the effects of variations in median configuration. Placement effectiveness plots were generated with vehicle dynamics tools for two barrier designs. The results showed effects on lateral placement locations resulted from atypical median configurations and in situations in which there was variation in the relative elevations of the roadways on a divided highway. The results suggested a need to consider the effects of transitions in the median configuration when the barrier type and the lateral position are selected for the full length of a project. The results enhanced understanding of the effectiveness of median barrier placement with various median configurations and barrier options.