Officials and residents are hoping a long-awaited contra-flow lane opening Wednesday on congested Farrington Highway will help ease afternoon traffic on the Leeward Coast.

The state Department of Transportation plans to repurpose one eastbound lane on the four-lane highway to allow for three Waianae-bound lanes and one town-bound lane from Piliokahi Avenue to near Nanaikeola Street — a corridor that creates a traffic bottleneck.

“There is a real capacity problem going into the Leeward Coast and out of the Leeward Coast daily,” said Ed Sniffen, who heads the DOT’s Highways Division. The goal “is to make sure we get the West side residents back home as soon as possible.”

Sniffen estimated that about 1,450 westbound vehicles pass through the 1.5-mile corridor during afternoon peak traffic every hour, with about 50,000 vehicles using Farrington Highway daily, compared with about 30,000 10 years ago.

The contra-flow lane is expected to be needed for one year. The cost of the project is $500,000, 80 percent of which is federal funds and 20 percent state money.

DOT will operate the lane and keep it open 4-7 p.m. weekdays. Crews will begin coning at 3:30 p.m., and it will take until 7:30 p.m. to close the operations.

Eastbound left turns at Helelua Street, Haleakala Avenue and Nanakuli Avenue will be restricted, and a detour is planned from Laumania Avenue through Pohakunui Avenue to Piliokahi Avenue for eastbound drivers who need to turn left.

Special-duty police officers will be stationed to monitor traffic flow and assist in case emergency vehicles need to pass. Sniffen said the DOT is also looking into installing speed bumps on Pohakunui Avenue.

Contra-flow operations will run in conjunction with another DOT project that will add a dedicated fifth turn lane in Nanakuli. The project is slated for completion in July, at which point Sniffen said officials anticipate there will be no need for the contra-flow lane. He said officials are considering another contra-flow lane from Lualualei Naval Road to Hakimo Road after the turn-lane project is completed, but will need to evaluate traffic volumes and impacts first.

State Sen. Maile Shima-bukuro (D, Kalaeloa-Waianae-Makaha) said residents for years have pushed for a contra-flow lane.

“I’m just so grateful to have this kind of response from DOT,” Shimabukuro said. “I’m very, very excited to see the contra-flow get started this week.”

Sniffen had presented the contra-flow plan to the Nanakuli/Maili Neighborhood Board, where some residents raised concerns about a previous plan for a detour route using the “bridge to nowhere,” which is part of the Waianae Coast Emergency Access Route that provides a connection over Nanakuli Stream, through Kalanianaole Beach Park, formerly named Nanakuli Beach Park. But Sniffen said officials decided against that plan because it would have affected beach park access and parking.

Other concerns were raised about buses backing up traffic in the one eastbound lane. Sniffen said the DOT is undertaking a project to relocate, consolidate and remove some bus stops.

DeMont Conner, a Nanakuli Homestead resident, described the contra-flow as “really good.”

“This issue has been going back and forth for a while,” he said. His wife, Rachel Kailianu-Conner, added that the contra-flow will hopefully “get people to appreciate that there is a way” to help ease traffic on the Waianae Coast.