This project will add a lane to I-66 in each direction from Haymarket to Gainesville in Prince William County.  During peak traffic times, one lane will be designated for High-Occupancy Vehicle (HOV) travel.  This project also includes the reconstruction of the I-66/US 15 Interchange, as well as widening a 2.5 mile stretch of I-66 to eight lanes (by adding one HOV lane, and one general purpose lane in each direction) between Route 29 and Route 15.