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Under Construction

I-66 and Route 15 Interchange Reconstruction

Constructing a new Diverging Diamond Interchange in Prince William County

Project Photos

Project at a Glance

Begin Date
September 2015

Est Completion Date
Fall 2017

$59 million

Lane Construction Corp.

Prince William

Northern Virginia

Christiana Briganti-Dunn, P.E., CCM
William Atkins, CCM

About the Project

In May 2014, the CTB awarded a $36 million contract to Lane Construction Corp. of Chantilly to design and build a diverging-diamond interchange (DDI) on U.S. 15 at I-66 to relieve congestion, enhance public safety, operations and capacity, and accommodate forecasted traffic demand in the area.

Diverging-diamond interchanges shift vehicles to the opposite side of the road and eliminate left turns that cross into oncoming traffic, improving safety. Traffic signals at each end of the interchange feature only two phases, reducing “red light” time for motorists and enhancing mobility. VDOT recently completed its first DDI on U.S. 15 where it crosses Interstate 64 at Zion Crossroads in Louisa County and has two more in the works in Roanoke and Blacksburg.

As part of this diverging-diamond interchange, the project will include constructing:

• Two longer bridges to carry U.S. 15 over I-66 with two crossover intersections;
• Ramp improvements (including a spur ramp to ease traffic flow from westbound I-66 to northbound U.S. 15 to westbound Heathcote Boulevard);
• Improvements on U.S. 15 from just north of the railroad tracks to just south of Heathcote Boulevard;
• Wider intersections on U.S. 15 at Heathcote Boulevard and Route 55, adding turn lanes to both; and
• A 10-foot-wide shared-use path on the east side of U.S. 15 for pedestrians and bicyclists.

Video Simulation - Morning Peak Period

Video Simulation - Afternoon Peak Period

Estimated Costs
Preliminary Engineering: $3 million
Right of Way acquisition and Relocation Assistance: $8 million
Design/Build Contract (Final Design, Utility Relocation & Construction), Contingency and VDOT oversight: $48 million
Total: $59 million

Traffic Impacts

Motorists can expect daily, single-lane closures during off-peak hours on Route 15 and Route 55 in the Town of Haymarket.  Access will be maintained at all times to private and business driveways and all I-66 interchange ramps.

Given the layout of the existing interchange, no complete stoppages of I-66 traffic flow are anticipated, as the nighttime traffic volumes can be detoured onto the exit ramps, through the Route 15 traffic signals and then back onto the interstate via the entrance ramps.

Please note the adjacent I-66 widening project also has traffic impacts in this area.


"Pardon our dust" meeting presentation (August 2015)
Revised Environmental Assessment (June 2015) and Appendices
Information meeting (October 2014)
    FHWA video - Diverging Diamond Interchange
    Displays: Overall Project, Traffic Flow, Peak Hour Volumes 2036
    Comparison Table - DDI vs. Flyover 
    Traffic Operations - DDI vs. SDR
Contract Award (May 2014)
Public hearing brochure, comment summary (March 2013) 
Information meeting brochure (March 2012)
Project Numbers
UPC: 100566
State: (FO) 0066-076-074, P101, R201, C501
Federal: IM-066-1 (341)

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Page last modified: Oct. 17, 2016