NOTE: If the road is classified as mH or higher and is wide enough for median segments at intersections to be >5m, you need to create two one-way segments. You can unset the checkbox for "Draw new roads as two-way" to help with this.
If an existing road is classified as mH or higher and is wide enough. Median segments at intersections should be >5m. To divide an existing road, create two one-way segments from each 2-way segment (preserving the traffic data in both directions). If you are not familiar with the technique for preserving traffic data in both directions, please work with an editor who is. We follow the [https://docs.google.com/presentation/d/1m8jgfYzGK_SxauaRtcmJvo5ScCfc81-TIbH23YmoxSU/edit#slide=id.p4 guidelines in this presentation on dividing roads]