Some 19,000 drivers a day should now have an easier and possibly faster route from Auburn to southbound I-5, with Monday's opening of a two-lane ramp from westbound Highway 18.

About 19,000 drivers a day are gaining an easier and possibly faster route from Auburn to southbound Interstate 5, now that work is done on the biggest piece of the Federal Way Triangle highway project.

A direct, two-lane diagonal ramp from westbound Highway 18 to southbound I-5 opened Monday. It replaces an old cloverleaf that was so short that drivers had to yield, or even stop, right after navigating a 270-degree curve.

“I always called it Federal Way roulette, because getting off these clovers and getting on the freeway was so dangerous,” said state Sen. Tracey Eide, D-Federal Way, at an opening ceremony.

A second connection, from eastbound Highway 18 to northbound I-5, will open next Monday, allowing a brisk departure from Federal Way toward Tukwila, Seattle and Renton.

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The $113 million project is funded primarily by state gas-tax increases approved in 2003 and 2005. Prime contractor Mowat Construction finished the two-year job ahead of schedule, said Lorena Eng, regional administrator for the state Department of Transportation.

In September, the new southbound ramp will add a spur offramp to Highway 161, which leads to Puyallup. Sidewalks along 161 aren’t done yet, but Eng said the state wanted to open the primary lanes to I-5 now.

Stan Vander Pol, president of Peninsula Truck Lines in Auburn, at Monday’s opening ceremony, said the new ramp will save at least five minutes per afternoon trip, because clogged intersections entering Federal Way will no longer create spillover congestion for the uphill traffic using Highway 18.

From 2005 to 2010, there were 604 crashes on Highway 18 at its I-5 approaches, a higher rate than at most interchanges, said project spokesman Mike Murphy, who said wrecks are now expected to decrease sharply.

Additional ramps are planned but unfunded.

Mike Lindblom: 206-515-5631 or On Twitter @mikelindblom.