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Dear MwRSF,

We have a reconstruction project of a freeway that has had CMC crash history and has had cable barrier installed in the median.  The project team indicated that they would like to reconstruct the median wide enough to not need cable barrier. 

The WisDOT thresholds for CMC is the same as the Caltran's threshold. 

Can MwRSF provide a recommendation on median width?

Appropriate median width for cable barriers is not a fixed distance. Rather the width is related to the traffic volume or ADT. previous research has shown that cross median crash rate (CMC) had a second order relationship with respect to ADT. As such, selection of appropriate median widths for use of cable barrier depends on the traffic volume and the benefit cost ratio of the addtion of the cable median barrier.

MwRSF conducted previous research into cross median crashes based on Kansas data. The research was detailed in TRP-03-206-08. For very high ADT roads, MwRSF would recommend large median widths of 100' or more in order to compensate for the increased propensity for CMC events due to the high traffic volumes. If median widths of this magnitude are not permissable, data from the Kansas study found that a median width of 70 ft or more were not recommended for cable median barrier unless ADT was extremely high or accident data determined a need for median barrier in a specific area.

Further details on guidance for cable median barriers and median width can be found in the attached report.