Dulles Greenway Plaza Backups

What a turnaround! From an embarrassing lack of traffic just two years ago the Dulles Greenway is now battling congestion. At least at its main toll plaza. Weekday traffic this summer has reached 41k veh/weekday compared to 12k veh/day in early 1996. The past few months backups have become common at the mainline toll plaza on the northern edge of Washington Dulles Airport. And this is summer in DC when a good portion of people normally take off to Nova Scotia or Wisconsin or somewhere cooler, and traffic typically drops 10% or more. Maybe in this long hot summer they have become more willing to pay tolls to get there quick?

Mark Manlove marketing mgr says the delays to patrons have been eroding the time advantage the Gway has relative to competitive free VA-7/28: “It has been getting quite bad, backups as far as 606 (Old Ox Rd overpass).”

The toll plaza has 14 lanes and in the am peak they run up to 9 inbound. But traffic has to divide at the plaza because of the complex interchange (with splits to the airport, to VA-28 and to the Dulles Toll Rd) immediately beyond the toll plaza so imbalances in queues occur. The throat to the plaza is rather short and it doesn’t take much for a bottleneck to occur and for traffic to back up onto the two travel lanes.

The plaza is designed for expansion to 18 toll lanes but for now the Gway sees the solution in trying to switch more patrons to electronic toll tags. They are already at 60% ET usage and are now shooting for 80%.

A high-milage rebate system for ET got the Gway up from 45% to 60% ET usage. Now the Gway is raising the weekday cash toll only from $1.50 to $1.75 for cars (>2 axles goes up 50c) while keeping ET rates the same and doing a major marketing push to encourage drivers to get Smart Tags, as the transponders are called here.

“80% is perhaps optimistic but this should get us well into 70s,” says Manlove, “then we’ll see what the backups are like and what else we need to do.”

He says that with 25mph roll-throughs an ET lane does about five times the hourly vehicles of manual collection. The Dulles corridor is in a spectacular economic boom being a major world center for internet companies and daily direct flights Dulles-San Jose are packed. It’s still a gap but the gap is closing on Vollmer Assoc much derided Gway traffic forecasts that were blamed for it defaulting on its debt in the early years.