A stretch of heavily traveled highway in Northern Virginia has become one of the longest work zones in the nation this summer.

About 1,500 workers are turning a 29-mile section of Interstate 95 into the state’s latest high-occupancy toll lane project. The long-term impact on commuting in the D.C. region is likely to be enormous, but the short-term effects of summer travel also will be significant.

While the work zone is long, it’s a pretty tight space for the crews. Lanes will close, traffic will shift and lengthy detours will sometimes be required.

“This is a fast-track project,” said Michelle Holland, deputy manager of communications for the Virginia Megaprojects office, a branch of the Virginia Department of Transportation that coordinates some of the state’s largest efforts at traffic relief. “We have to get things done expeditiously.”

Work began last summer, but this summer and fall, drivers are likely to encounter the peak of the project’s disruptions. It’s scheduled to be completed in very late 2014 and open in early 2015.

Here’s what to look for as you plan summer commutes and getaways.

Increased congestion

The 95 Express Lanes construction zone, stretching from just inside the Capital Beltway in the north to Garrisonville Road in the south, includes several different work environments. In the north, today’s High Occupancy Vehicle lanes are being converted into high-occupancy toll lanes. To the south, beyond the HOV zone, new lanes are being built.

Much of the work is in the I-95 median, where the new lanes will open, but there’s also considerable activity along the shoulders. Throughout the summer, watch for:

●Extensive lane closings and delays at off-peak hours day and night.

●Occasional full closings of I-95 and overnight detours.

●Slow-moving trucks entering and leaving the work zone in the median.

●Reduced access to shoulders.

Drivers already encounter these conditions, and another major disruption is scheduled this coming weekend. The express lanes project is scheduled to close all lanes of I-95 South near Telegraph Road Bridge in Quantico on Friday and Saturday nights so that workers can place steel beams for the new Telegraph Road bridge over the southbound lanes.

Starting at 9 p.m., crews will close a southbound lane. After midnight, all the southbound lanes will be closed and drivers will be detoured east from the Russell Road exit to Route 1, then south so they can return to I-95 at Garrisonville Road. The detour will add about 25 minutes to trips.

95 vs. 495

Jamie Breme, the public affairs manager for Fluor-Lane 95, the company building the new lanes, took me on a tour of the northern portion of the work zone to illustrate the compact nature of the work zone south of Springfield, where a flyover bridge that will link the 95 Express Lanes with the Fairfax County Parkway.

“There are lots of people to keep moving,” she said.

As traffic roared south just beyond a concrete barrier, we watched workers building up the fill that will support the flyover on the west side of I-95. Right now, the bridge exists in disconnected sections. Drivers are most likely to notice the section in the middle of the highway, which looks like it’s built from concrete puzzle pieces.

Breme and Holland, both very familiar with the now-complete 495 Express Lanes construction, compared and contrasted that now-complete project with the I-95 one.

At 14 miles, the Beltway project was shorter, but more bridges and interchanges had to be rebuilt. In fact, on the I-95 project, much of the bridge construction involves flyover ramps that will link the express lanes with regular travel lanes rather than cross over the entire interstate.

Traffic patterns are different. The morning rush in the I-95 work zone starts earlier and the afternoon rush begins earlier. Work schedules had to be adjusted to take that into account.

The detours are different, too. On the Beltway, interchanges are fairly close together. When a steel lift required the complete shutdown of one side, drivers often could follow a relatively short diversion before resuming their trips. On I-95, interchanges tend to be farther apart, and the diversions for shutdowns are longer. Sometimes, a lengthy detour along Route 1 will be the best alternative.

During the very late hours when such detours are required, Route 1 should have the capacity to handle the traffic, said Toymeika Braithwaite, the express lanes’ public affairs manager for the Megaprojects office.

Travel tips

The D.C. region’s drivers may react to this warning about extra congestion on I-95 by saying, “How can we tell?” Unfortunately, this summer, labor will be so intensive that they almost certainly will be able to tell. Here are a few summer survival tips:

●Expect continued daytime lane closings on I-95 and nightly lane closings on both the regular and the HOV lanes.

●Expect full closings of the HOV lanes on weekends, which seriously shrinks the interstate’s capacity.

●Watch for announcements about these closings and also about the occasional complete closings and detours for the overnight steel operations on weekends.

●An HOV lane shift is scheduled to occur in late summer.

●If you live in Prince William County and commute to Tysons, consider taking the PRTC’s Tysons Express bus. Virginia Railway Express is an option for other commuters.

●Read those electronic message boards along I-95 that warn about upcoming work.

●Check out www.getaroundva.com, where you can sign up to receive electronic alerts. This will be especially helpful if you make only occasional trips on I-95 for summer getaways.

●Consider I-95 alternatives such as routes 17 and 301, where there are no major projects this summer.