(Virginia/MAR DDI additional Guidance) |
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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. | 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: | Virginia follows the national [[#Diverging diamond interchange (DDI)|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 [[File:Exit_left_TIO_on_DDI.png|thumb|center|Exit Left TIO on second exit (driving on left side of road) in DDI]] | 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 [[File:Exit_left_TIO_on_DDI.png|thumb|center|Exit Left TIO on second exit (driving on left side of road) in DDI]] | ||
2) All elevations should be ground for at grade connections, unless there is a bridge, then make proper elevation change. | 2) '''Elevation''' All elevations should be ground for at grade connections, unless there is a bridge, then make proper elevation change. | ||
Revision as of 01:50, 15 July 2017
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) Elevation All elevations should be ground for at grade connections, unless there is a bridge, then make proper elevation change.