VDOT map shows the location of the shoulder project, scheduled to be open to traffic by year’s end.

A project to improve traffic on one of the most congested sections of the Capital Beltway in Virginia is getting underway this weekend.

By the end of the year, the Virginia Department of Transportation hopes, it will have made a rush-hour travel lane out of the left shoulder on the inner loop between the 495 Express Lanes merge and the George Washington Parkway. This is a heavily used section of the Beltway during both morning and afternoon commutes.

The work is scheduled to begin after 9 o’clock Sunday night when crews put down temporary striping on the inner loop to shift the northbound lanes from just south of Old Dominion Drive to the GW Parkway. Lanes will close overnight as the workers proceed with the restriping.

When they’re done with that initial work, drivers will need to watch for the lane shifts and reductions in the size of the shoulders as the construction proceeds.

Susan N. Shaw, VDOT’s regional transportation program director, said during a public meeting about the project last fall that the shoulder opening is not a grand solution to the traffic congestion north of Tysons, but it should make commuting easier than it is now. VDOT is working with the space available, rather than widening the footprint of the Beltway.

The shoulder program will expand the capacity of the 1.8-mile zone, but not the capacity of the roadways feeding traffic into it. Today’s traffic — about 95,000 vehicles a day — will just have more room to spread out, at least for 1.8 miles.

VDOT’s plan is to use green and red lane markings similar to those that designate when the Interstate 66 right shoulders are open and closed to traffic. To do this project within the existing footprint of the Beltway, the four regular lanes will be narrowed from 12 feet to 11 feet. But the left shoulder lane also would become 11 feet wide, with at least a 2.5-foot clearance from the median barrier. At off-peak times, when the shoulder reverts to a breakdown lane, that’s roomier than what’s available now for drivers in emergencies.

The shoulder lane will be a shade of gray distinctive from the coloring of the regular travel lanes, Shaw said.

VDOT’s plan is to work off-peak and at night in what’s a fairly tight construction schedule for an end of 2014 opening.