Three-level diamond interchange
From Wikipedia, the free encyclopedia
A three-level diamond interchange is a type of highway interchange where through traffic on both main roads is grade-separated from intersections which handle transferring traffic.[1] It is similar in design to a three-level stacked roundabout except for its use of (usually signalled) conventional intersections, and can be thought of as two diamond interchanges fused together.
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[edit] Description
In a three-level diamond interchange, the two main roads are on separate levels, and on a third level, usually (but not always) in the middle, there is a square of one-way roads. The square circulates clockwise where traffic drives on the left, or anticlockwise where it drives on the right. At each corner of the square is the terminal of an exit ramp from one main road and an entrance ramp to the other main road. Traffic transferring from one road to the other to make an overall right turn only passes through one corner of the square, at which point a right turn is made. Transfer traffic making an overall left turn must proceed straight through the first intersection it encounters, turn left at the next, and then proceed straight through a third intersection to enter the other main roadway.
In the United Kingdom, such junctions use a circular road instead of a square, in the form of a "giant roundabout".
[edit] Examples
Three-level diamond interchanges are most common in urban settings where the right-of-way for a new interchange must be kept to a minimum.
| Location | First Route | Second Route | Notes |
|---|---|---|---|
| Cedar Rapids, Iowa |  I-380 |
 IA 100 |
Collector/distributor roads intersect. |
| Detroit, Michigan |  I-75 (Walter P. Chrysler Freeway) |
 M-1 (Woodward Avenue) |
|
| Detroit, Michigan |  M-102 (8-Mile Road) |
two locations | |
| Jefferson City, Missouri |   US 50/US 63 northbound |
 US 54/US 63 southbound |
A flyover ramp allows southbound US 63 traffic to join US 50 east, bypassing one intersection. |
| Asheville, North Carolina |  I-240 |
 US 70 |
I-240 Exit 7 |
| Springfield Township, Pennsylvania |  I-476 |
 US 1 |
|
| Welch, West Virginia |  US 52 (King Coal Highway) |
 US 121 (Coalfields Expressway) |
As of 2008, grading has been completed for interchange but interchange itself has not been constructed. |
| Wheeling, West Virginia |  I-470 |
  US 250/WV 2 |
Entire interchange is elevated above city streets. |
A few examples of this can also be found in Texas; however, the interchanges usually include the Frontage Roads as well. If the traffic accounts increase the interchange is usually converted into a Stack interchange.
[edit] References
- ^ Indiana Department of Transportation, InterchangesPDF (203 KiB), pages 21 and 22
[edit] External links
- Kurumi's Field Guide to Interchanges: Volleyball Interchange
- Aerial view of a three-level diamond interchange (Interstate 380 and Iowa Highway 100 in Cedar Rapids, Iowa). Highway 100 runs from left to right; Interstate 380 runs from top to bottom.
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