An important traffic improvement scheduled for this weekend could ease one of the D.C. region’s worst bottlenecks.

This one is better that just ending a stretch of road work. It will remove a problematic merge and should improve safety. If the result is what planners hope, eastbound drivers on Interstate 66 will have a much easier time merging onto the Capital Beltway’s inner loop and Beltway drivers won't encounter so much slow-moving traffic in the left lanes.

The source of the improvement is a new flyover ramp that is part of the high-occupancy toll lanes project. The ramp will take traffic exiting eastbound I-66 and deposit it on the right side of the inner loop. That traffic now merges on the left side of the inner loop, blending fast-moving Beltway traffic with slower-moving traffic coming off the ramp. Some of that traffic now entering on the left side must move over all the way to the right in a short distance to reach the exit for Route 7 into Tysons Corner. Those drivers will have a much easier time once this change is made.

Reconstruction of the Beltway/I-66 interchange is one of the most complex parts of the HOT lanes project, and the opening of the flyover ramp won’t end the work, or completely end the traffic congestion at the interchange.

For example, the HOV exit from the left side of I-66 onto the left side of the inner loop still will be in place, and that also contributes to the traffic congestion on the Beltway. (Eventually, that left ramp will lead into the HOT lanes.)

There’s also likely to be some congestion generated during the learning period when drivers get acquainted with the flyover ramp. Some of the drivers who now use the HOV lanes may want to get over to the right before they reach the interchange so they can take advantage of the ramp that will put them closer to the Route 7 exit.

That could mean a little more lane-jockeying in a very congested part of eastbound I-66.

Meanwhile, the interchange reconstruction will continue. Looking ahead, planners say that by fall 2012, the inner loop merge lane will be extended north all the way to Route 7, adding a fifth lane along the Beltway in that congested area.

Some work leading up to the flyover ramp’s opening is scheduled for Friday night. From 9 p.m. Friday to 9 a.m. Saturday, crews will close both exits from I-66 east to the inner loop as well as three lanes on the inner loop. Detours will be in place, but it would be best to avoid the area around the interchange because congestion is likely.

By 9 a.m. Saturday, the new ramp should be open.