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.

Contents 1 Description 2 Examples 3 References 4 External links

[edit] Description

In a three-level diamond interchange, the two main roads are on separate levels, and on a third level, usually 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.

[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.
Sioux City, Iowa	I-29	US 77
Detroit, Michigan	I-75 (Walter P. Chrysler Freeway)	M-102 (8-Mile Road)	I-75 uses frontage roads.
Detroit, Michigan	M-102 (8-Mile Road)	M-1 (Woodward Avenue)
Detroit, Michigan	M-102 (8-Mile Road)	M-10 (John C. Lodge Freeway)	Includes flyovers from northbound M-10 to westbound M-102, eastbound M-102 to southbound M-10, and westbound M-102 to northbound M-10. M-10 uses frontage roads.
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
Fairfax County, Virginia	Fairfax County Parkway	US 29	The south end of West Ox Road also meets this interchange.
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.
Wauwatosa, Wisconsin	US 45	WI 190 (Capitol Drive)	An access road for the adjacent Harley-Davidson plant is also part of the interchange.

A few examples of this can also be found in Texas; however, the interchanges usually include the frontage roads as well. If the traffic amounts increase the interchange is usually converted into a stack interchange.

[edit] References

1. ^ 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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