Virginia/Mid-Atlantic Region guidance on Divergent diamond interchanges (DDI)
DDIs are the new rage in transportation engineering. They can save a lot of room for a controlled entrances and exits from a freeway/highway and they are supposed to improve travel flow. Because a DDI has traffic flowing counter to the normal US experience, you drive on the left side of the interchange for a while, the first time can be a harrowing experience for drivers. Virginia follows the national Diverging diamond interchange (DDI) with two additional points:
1) Exit Left TIO When driving on the left side of the road add an "Exit Left" Turn Instruction Override for the second exit to the freeway/highway in both directions. Example
2) All elevations should be ground for at grade connections, unless there is a bridge, then make proper elevation change.