SOUTH PORTLAND — The Maine Department of Transportation is asking for the public to be patient and to plan ahead, as it prepares to close a major thoroughfare between Portland and South Portland.

Jeraldine Herrera, spokeswoman for the state agency, said travel lanes in both directions on the Veterans Memorial Bridge will be closed for five nights to allow construction crews to install a new underground communication conduit.

That conduit, which currently runs underneath the existing bridge, must be encased in concrete and extended to the new Veterans Memorial Bridge that is under construction next to the old bridge.

The closure will begin Sunday night, Oct. 23, and last through Thursday, Oct. 27. The closure will run from 7 p.m. to 6 a.m.

Detour signs and message boards informing commuters about the situation will be installed.

Drivers leaving Portland and heading for South Portland should use the Fore River Parkway to access Interstate 295. Traffic heading north to Portland from South Portland should use Interstate 295 and use Exit 5 to access the Fore River Parkway.

Construction of the new bridge is on schedule and expected to open to traffic by next summer.

The old bridge will be completely removed in December 2012.

Herrera said the bridge replacement project, which began in March 2010, will cost about $63 million.

An estimated 22,000 vehicles a day travel over the current Veterans Memorial Bridge, which was built in 1954.