Skip to main content

Remaining stretch of I-485 will feature three unique types of interchanges

The remaining 5.4 miles of I-485 currently under construction in Mecklenburg County will feature three unique interchanges.  All three are in use elsewhere within the country, but would be the first ones built in the Tar Heel State.

At two of the interchanges, the new designs are considered upgrades (in traffic flow and cost savings) versus what had originally been planned.

The interchange design names are Split Diamond, Diverging Diamond, and Turbine.

Heading East from the current terminus at NC 115, the three new interchange designs run as follows:

The Split Diamond interchange will be located at Prosperity Church Road.  This interchange will consist of two access roads and six roundabouts.

Split Diamond Interchange with Prosperity Church Road (NCDOT)
The Diverging Diamond Interchange (DDI), first used in Missouri, is starting to catch interest in North Carolina.  The interchange design, actually reverses the lanes of traffic on the surface/cross street.  This will be located at the Mallard Creek Road exit on I-485.

This design replaces a planned Single Point Urban Interchange (SPUI) for 485 and Mallard Creek.


We covered a Diverging Diamond Interchange back in October when NCDOT announced it is considering the design on NC 133 where it meets the US 74/76 freeway in Leland.  These two intersections, along with two more on nearby Interstate 85 at NC 73 and Poplar Tent Road, are some of seven prospective locations for this new style of interchange.

Finally, the Turbine - an interchange that has all left turn movements circling around a central bridge in a clockwise direction, creating a seamless movement between the two highways.  This replaces the previously planned four-level stack interchange.  (Similar in design to where I-77 and 485 meet in Southern Mecklenburg County.)

The new "Turbine" interchange at 85/485.  (NCDOT)      
According to NCDOT, this type of interchange will cost less to build and maintain, take up less space, and allow for less interruptions to existing I-85 traffic during construction.


Story Links:
Last Outerbelt juntions to display unique functions ---Charlotte Observer
I-485 Charlotte Outer Loop ---NCDOT

Comments

Froggie said…
NCDOT apparently doesn't see it as such, but I-40/Exit 195 (at NC 109) in Winston-Salem, is very much a split-diamond.
Anonymous said…
Should that be counterclockwise, or am I missing something? (Maybe clockwise in countries that drive on the left...)
Reminds me of my Alexandria Orb proposal:

http://wwwtripwithinthebeltway.blogspot.com/2007/02/alexandria-orb-page-one-news-december.html

http://wwwtripwithinthebeltway.blogspot.com/search/label/Alexandria%20Orb

Popular posts from this blog

The story on how the unbuilt US 40 Expressway in Brownsville took 40 years to complete.

For nearly four decades, the four lane US 40 just east of Brownsville came to an abrupt end - shown in the photo above - at Grindstone Road in Redstone Township.   In the late 1960s, what was then the Pennsylvania Division of Highways (PennDOH) extended a new four lane alignment of US 40 eastwards from Broadway Street slightly over one mile to Grindstone Road where an incomplete diamond interchange was built.  Earlier in the decade, PennDOH had built a four lane US 40 in Washington County into Brownsville complete with a new crossing over the Monongahela River known as the Lane Bane Bridge.  This new highway and bridge allowed US 40 to bypass the older Intercounty Bridge and downtown Brownsville. 

After this new highway opened, nothing would happen to it for nearly forty years.  US 40 traffic would use the ramps for this planned diamond interchange and then jog on Grindstone Road briefly before continuing towards Uniontown on the original National Road. 
What is unknown (at least to…

The story of the Boy Scout Ramps on Interstate 79 North in NW Pennsylvania

If you are traveling on Interstate 79 North of Pittsburgh, you may notice the remnants of a set of off and on ramps at mile 100 just north of Exit 99 (US 422).  There's a story behind these ramps.  Forty years ago, these ramps were built specifically for two Boy Scout Jamboree's that were held at Moraine State Park - 1973 and 1977.  The ramps purpose were to provide access to the north shore of Lake Arthur where the bulk of the festivities and campsite for the Jamboree were located.  (Lawrence County Memories has a great write up and map of the festivities on its site.)

Not long after the Jamboree ended the ramps were abandoned.  There are still remnants of the Boy Scout Ramps today.



Above: Sattelite view of the Boy Scout Jamboree Ramps. 
Below: A view of the ramps from I-79 South.



The google street view image above gives a view along West Park Road of where the set of ramps intersected the highway.  The ramps provided direct access to North Shore Drive (which is the right tur…

The few clues of the Northern Durham Parkway

Sometimes when you look through a box of maps for the first time in five years, you come across something you may have easily over looked.  Such was the case when I found a 2004 (so rather recent) map of Raleigh.  This map was made by the Dolph Map Company for WakeMed.  In the Northwestern corner of Wake County, there were two items to the map showing roads that are still not in existence 13 years later.

The road is the Northern Durham Parkway - this is a proposed 19 mile highway from US 501 north of Durham to the Raleigh-Durham International Airport.  The first proposals for this highway date back to 1967 when Eno Drive-Gorman Road was listed on the Durham Area Thoroughfare Plan. (1)  Other proposals called the highway the Northwest and Northeast Durham Loop. (2)  The route would serve as a northern and eastern bypass of Durham almost serving as a near loop.  The route was fought vigorously for three decades by the Eno River Association citing concerns for the the Eno River, nearby n…