Recently Completed: Frederick County - I-81 Exit 310 at Route 37 (Kernstown Interchange)

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This project reconstructed the interchange ramps on Interstate 81 exit 310, at Route 37 (south) in Frederick County. The interchange configuration features a “spread diamond” interchange, which widens and spreads the ramps outward from their previous configuration. This design provides additional turn storage and adds dual left- and right-turn movements to move traffic more efficiently.

The interchange is being designed with future “scalability”, which can accommodate changes in traffic patterns and traffic volumes. The design can accommodate future conversion of the interchange to a partial cloverleaf, a full cloverleaf with collector-distributor lanes, or a multi-level semi-directional interchange. The final build-out of the interchange will be done in several future phases. In association with the interchange improvements, the Crosspointe developer will continue the extension of Route 37 east of I-81 and build it as part of their construction site.

The Federal Highway Administration approved the Interchange Modification Request (IMR), on April 18, 2007. The IMR consists of a three-phase approach to improving the interchange.

Phase one included right of way, utility relocations and construction of the spread diamond interchange. Relocation of Tasker Road and Hillandale Lane to the east is also included in the project, to include temporary ramps from Route 37 to Tasker (the ramps will be removed when Route 37 is extended east to the future Warrior Drive).

Future phase two may include a partial cloverleaf loop and/or widening of the Route 37 bridge over I-81. All phase two work depends on future traffic demand and available transportation funding. Future phase three may be the completion of cloverleaf or flyover ramps. The cloverleaf option may also include collector distributor lanes. Collector distributor lanes run parallel to the interstate roadway, taking traffic of the mainline a mile to half mile prior to the interchange ramps. All phase three work depends on future traffic demand and available transportation funding.

On Interstate 81 in 2015 traffic counts for this location are projected to be 57,270 south of Route 37 and 51,189 north of Route 37. In 2035 traffic counts for this location are projected to be 85,100 southbound, south of Route 37 and 76,064 northbound, north of Route 37.


The project will help alleviate tight turning maneuvers currently being experienced by drivers at this interchange ramps and on Route 37 and U.S. Route 11. The design will allow more lane capacity, including many dual-left turns, to accommodate more vehicles waiting to make a left-turn onto Route 37 and the I-81 ramps.


Contact Info:

Robert Good, P.E.

Project Photos

UPC: 75881

State ID: 0081-034-127,P101, R201, C501

Federal ID: NH-081-3(157)

Lat/Long: 39.120278, -78.191667

Locality: Frederick

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Completed interchange - Summer 2017
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Completed interchange - Summer 2017
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Phase 1 Design Plans
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Phase 2 Design Plans
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Phase 3 Design Plans

Page last modified: Sept. 13, 2018