Travelers along portions of two of South Roanoke County's busier secondary highways -- Merriman Road and Colonial Avenue -- will face detours for several weeks this summer.

Both roads feed commercial or industrial districts as well as residential neighborhoods.

The Merriman Road project will allow for the creation of a roundabout near the entrance of the new South County Library at its intersection with Meadowlark Road. The road will be closed to through traffic from June 11 through Aug. 23 between Chaparral Drive and Starkey Road.

The Colonial Avenue project involves a stretch between the North Cross School entrance and Colonial Place Drive as the Virginia Department of Transportation alters the road to improve sight distances. It will be closed from June 14 through July 23.

David Holladay, planning administrator for the county, said motorists will likely see more instances in the future of roads closing for construction, rather than narrowing to one lane.

"It's faster and more economical than trying to maintain one lane of traffic," he said, particularly for projects such as these two, which both involve significant alterations of the grade or road level.

Closing the roads will make the work "much more efficient, and makes it a much safer construction site."

Although both of those sites involve thousands of cars per day, two smaller projects in the western side of the county will inconvenience fewer people, but will block their routes completely for short times.

Dry Hollow Road will be closed from 8 a.m. until 4 p.m. on June 11 to replace a short bridge over Dry Hollow Branch. VDOT crews tried to replace the span last summer, but high water in the branch prevented the work.

Holladay said the parts for the new bridge have already been created, tested for fit and are ready to install.

Because Camp Roanoke and about a dozen families are located on the far side of the bridge, the county's fire and rescue department will station vehicles on that side during construction in case of an emergency, Holladay said.

Then in July, probably on the 30th, a similarly small bridge on Poor Mountain Road will be replaced as well, necessitating closing the road. That project will be done by a private contractor between 9 p.m. and 9 a.m., Holladay said.

Both bridge projects depend on good weather to be completed in their single-day schedule.