The state's extended new zipper lane — providing a continuous 15-mile freeway express route for O'ahu's carpooling commuters — opened yesterday with few problems, officials said.

"Altogether, it went very smoothly," Transportation Department spokesman Scott Ishi-kawa said.

The new three-mile section of the zipper lane connects the original seven-year-old zipper lane on H-1 Freeway with the start of the Nimitz Highway Contraflow lane that opened in 2003.

Before the new segment was opened, cars with two or more passengers had to merge with regular freeway traffic before Honolulu International Airport, creating a bottleneck that often slowed traffic to a crawl. Now, they can get all the way from the H-2 Freeway merge to town in their own lane.

"Traffic flowed pretty good all the way to town," said North Shore resident Carla Kishinami, who joined the zipper lane at its new entrance just before the airport. "Traffic was very light yesterday so I don't know how much time we saved, but it felt a lot safer not having to merge back onto the freeway."

The zipper lane extension, built at a cost of $9 million, is part of a continuing effort to ease traffic congestion for more than 80,000 morning commuters coming to town from Leeward and Central O'ahu.

Officials said opening the 1.7-mile Nimitz Highway Contraflow Lane has saved those motorists between 10 and 20 minutes of commuting time each day. However, they did not count how many drivers used the zipper lane yesterday and didn't try to estimate how much time it saved drivers.

"We'll do that later after the novelty dies down," Ishikawa said.

Ishikawa said traffic on the zipper lane, as well as the regular freeway lanes, appeared light and moved quickly yesterday despite a couple of stalled vehicles.

A bigger test of the new system will come Monday, however, when more than 40,000 college and high school students return to school, significantly increasing the number of commuters on the road.

"That will be the real test," Ishikawa said.

Reach Mike Leidemann at mleidemann@honoluluadvertiser.com.