I-66 at US Route 15 Diverging Diamond Interchange (DDI) Grand Opening

T3 Design has been heavily involved in the design of the first DDI in the Northern Virginia Region, providing support for the traffic analysis, traffic signal design, maintenance of traffic plan, traffic signal timings, and public involvement.

T3 Design participated the Public Hearing meeting held by Virginia Department of Transportation at Bull Run Middle School in Haymarket on December 7 and 13, 2016. During the Public Hearing, T3 Design staff assisted VDOT officials in demonstrating the “drive-through” on a model DDI on the floor of the room. 

The night of January 27 through January 28 of 2017, while bone chilling cold, was exciting and heart-warming for T3 Design staff: we implemented and tested the signal timing plans to ensure the proper operations of the signals and to ensure the grand opening on January 28, 2017 would be flawless.

T3 Design observed the various traffic conditions after the grand opening for any needed modification of signal timings.

The DDI configuration on US Route 15 at I-66 that replaces the existing traditional diamond interchange, provides numerous advantages among which are:  congestion relief, enhanced public safety, smoother traffic operations and increased capacity.

T3 Design is proud to be part of the design and construction team to help mitigate traffic conditions in the Northern Virginia Region.

Related links:

VDOT I-66 and US Route 15 DDI Interchange Reconstruction Official Website:



VDOT Public Hearing published on Fauquier Times:


WTOP I-66 and US Route 15 DDI Interchange Advertisement News: