WAIMANALO — Within months, the state plans to launch the first phase of what could be a $50 million, multiyear project to improve safety and ease congestion through much of Waimanalo, according to the Department of Transportation.

The improvements on three miles of Kalaniana'ole Highway, long sought by area residents, include new left-turn lanes in high-traffic areas and pullouts for buses and other vehicles.

The work will be done in phases over the next six years and cost between $35 million and $50 million, making it one of the area's biggest construction projects in years, officials said.

The changes will make it easier for other traffic to continue through the Windward community, which sometimes experiences rush-hour and weekend traffic congestion that rivals anything in urban Honolulu. One thing the project won't do, however, is widen the highway to four lanes at any point.

"The residents were very clear that they wanted improvements without losing the country feel of the town," said Transportation Department spokesman Scott Ishikawa. "We heard that loud and clear."

Ultimately, the improvements call for left-turn lanes at seven intersections where cars frequently enter or exit the highway, and bus pullouts where space is available, Ishikawa said.

Wilson Kekoa Ho, head of the Waimanalo Neighborhood Board, said residents welcome the improvement project.

"We're glad that they're doing it in a way that will help us fight gridlock, but allow us to keep the country feel of our community," Ho said. "It's been a safety and convenience issue with us for years."

Ho said Waimanalo residents have been patiently waiting for the improvements even as traffic has worsened in recent years.

"There's a lot of traffic moving between Hawai'i Kai and Kailua all the time, and it really backs up as people try to enter and get off the highway, especially on weekends," he said.

"We deal with it Waimanalo-style by letting others make their turns or waiting ourselves to enter the highway, which makes the wait even longer."

Ultimately the improvements will extend all the way to Waimanalo Beach, not far from where the state Department of Hawaiian Home Lands plans a large new development, Ho noted.

The final phase of the roadwork isn't expected to be completed until at least 2013, Ishikawa said

The work also will improve sidewalks on the mauka side of the highway between Kumuhau and Inoa'ole, which includes the commercial center of town and a part of the highway fronting Waimanalo Elementary and Intermediate School.

Areas of Kalaniana'ole Highway that don't have a sidewalk will receive a new paved shoulder to help improve safety for bicyclists, pedestrians and horse riders.

Existing utility poles will either be removed or relocated, and wiring for highway lighting will be placed underground, Ishikawa said.

Reach Mike Leidemann at mleidemann@honoluluadvertiser.com.