Opening the shoulders of Interstate 66 for buses is one of the simpler plans to ease the commute in that congested corridor, but it still took a while. Now, the Virginia Department of Transportation has set March 23 as the date for launching the program inside the Capital Beltway.

As of that Monday, VDOT-authorized commuter buses will be allowed to drive along the highway shoulder to get around slower traffic. The first authorized user is PRTC’s Omniride buses. But VDOT officials hope to have agreements with other bus operators so they too can participate in the pilot program later this year.

The transportation department will survey bus operators, riders, its own staff and police to evaluate the program over the course of about a year.

The shoulder lane program is simple compared to other I-66 projects, such as setting up high-occupancy toll lanes or the Automated Traffic Management system. But it does have its complications.

The key factor was solving the safety issues for everyone involved, including the commuters driving in the regular travel lanes. VDOT staff did test rides with bus operators to identify the sections of I-66 where shoulder travel would be safe. In some spots, the shoulders needed to be widened and strengthened. Trees had to be trimmed. New signs had to be placed. The improvements cost about $600,000, VDOT said.

Operating rules had to be set: The authorized bus operators can use certain segments of the I-66 shoulder when they encounter traffic moving at less than 35 mph in the regular lanes. On the shoulders, they can drive at a maximum of 25 mph.

The segments where the buses can use the shoulders add up to 6.3 miles, linking with a 1.3-mile stretch of the Dulles Connector Road where shoulder travel already is permitted.

The new segments on I-66 are: Eastbound from the Route 29 overpass near Spout Run Parkway to North Quinn Street, westbound from beyond the Rosslyn Tunnel to the Route 29 overpass near Spout Run Parkway and westbound from the North Quincy Street underpass to the auxiliary lane beyond North Fairfax Drive.

For drivers, this adds to the challenge of I-66 at rush hours. They will need to pay attention to the lane-shifting by the buses, particularly when the buses move from the shoulders back into the regular lanes. They could do that either when they approach the end of an approved segment of shoulder travel or when they encounter a motorist who needed to use the shoulder for its original intent: a breakdown lane.

The program, if successful, creates an obvious advantage for bus commuters. They should get a more reliable trip, because they’re not getting stuck in the same traffic as everyone else. The drivers who must now pay closer attention to the buses’ movements could think of it this way: If bus travel becomes more attractive, it should pull some commuters out of cars and onto buses, opening up more lane space for the remaining drivers.