How do commuters have the courage to get out of bed when they face a drive through the Interstate 66 corridor?

The national study showing that the D.C. region has the worst congestion in the nation merely supplies bragging rights. It doesn’t pinpoint troubles on any particular route. But a new study for a Virginia transportation program provides a pavement-level view of the misery along the 25 miles of highway between Route 15 in Prince William County and the Capital Beltway.

This recently released study, called a Tier 1 Draft Environmental Impact Statement, was prepared by federal and state transportation officials as part of a lengthy review of the problems along the I-66 corridor and the programs that could ease them.

It doesn’t announce solutions, but it does a really good job certifying the problems. Here’s what researchers found:

Profile of a highway

I-66 is the main east-west interstate highway in Northern Virginia. The main line and its feeder roads serve the District; Arlington, Fairfax, Loudoun and Prince William counties; and many municipalities along the way. (Virginia has been studying I-66 inside the Beltway separately.)

A map of Interstate 66

Regular and high-occupancy vehicle lanes accommodate drivers and bus riders. The Orange Line, Metro’s second-busiest, runs along the middle of the highway for part of its route.

A small portion of the interstate’s drivers go the distance in this corridor. About 7 percent of the eastbound drivers who travel the highway between Nutley Street and the Beltway begin their morning trips west of Route 15. By contrast, 42 percent of the morning traffic enters the highway at Route 123 or Nutley Street, much closer to the Beltway.

Bad, and getting worse

The pipeline isn’t big enough for the job it’s being asked to perform.

More than half of the roadway miles in the peak direction each morning are so congested they are at or near the point of failure in their ability to serve travelers. During the afternoon peaks, nearly two-thirds of the travel miles fall to that level of poor service.

The eastern portion of the corridor, near the Beltway, routinely experiences four to five hours of rush-hour congestion in each direction.

Looking ahead to what conditions might be like in 2040, the researchers predict further deterioration because of population and employment growth. This would not only make the rush-hour traffic heavier but also make the peak periods longer, as many commuters travel earlier or later to escape the worst of it.

Peak-period congestion in each direction between Nutley Street and the Beltway is likely to increase to eight and 10 hours a day.

Meanwhile, the rest of the corridor is subject to the same trend. The number of daily congested hours in the midsection will probably grow from two to four to as many as six. The west side’s congestion could grow from an hour or less to five or six hours.

Choke points

Connoisseurs of congestion can break down the problem further, down to the ramps, merges and interchanges that cause particular difficulty. Many will see their daily experiences confirmed in the researchers’ findings and will notice how many familiar bottlenecks will be rated as failures by 2040.

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.