Route 234 Bypass interchange. The merge for northbound traffic on the Route 234 Bypass (Prince William Parkway) to I-66 east will probably deteriorate from really bad to utter failure during the morning peak.
Route 234 Business interchange. The ramp from Route 234 Business (Sudley Road) to I-66 east will probably be in a failing state of service during the morning peak by 2040 because of the short acceleration ramp. In the afternoon peak, the same will be true for the off ramps because of heavy traffic. On Route 234 Business, four traffic signals within a half-mile create backups that affect the off-ramp traffic, as well as the through lanes.
Route 29 east interchange. At the easternmost of the two I-66 interchanges with Route 29, the merge areas on I-66 will be at a failing level of service during the peaks. Here also, the closeness of the traffic signals can back up traffic from one signal to the next.
I-66 between Routes 29 and 28. I-66 east slows because of heavy traffic entering from the easternmost Route 29 interchange and heavy traffic exiting at Route 28.
Route 28 interchange. The ramps from I-66, which are performing poorly now, will be in a state of failure at peak periods. Short acceleration lanes on Route 28 make merging difficult, and that causes traffic to back up to I-66 during peaks. There’s a left-turn signal for southbound traffic intending to go east, but the volume in the left-turning area often exceeds the space provided, so traffic backs up into a southbound through lane.
Fairfax County Parkway interchange. The difficult merge areas on I-66 at the parkway interchange will continue to deteriorate and be failing by 2040.
Route 50 interchange. East of this interchange, I-66 goes from eight lanes to six, and the shoulder is used as a fourth lane in the peak direction. Going east, congestion is a daily problem because of the heavy traffic entering from Route 50 on short acceleration lanes. The closeness of the access points for Fair Oaks Mall also hurts traffic flow.
Route 123 interchange. Acceleration lanes are too short for the conditions, so drivers have a tough time merging. That causes traffic to slow on the through lanes.
Nutley Street interchange. This overburdened interchange is the access point for the Vienna Metro station. The demand on the merging areas is going to exceed capacity, adding to the congestion cars and buses face.