Highline residents have a stake in a transportation funding package approved by the three-county Regional Transportation Investment District Planning Committee.

If voters agree this fall, money would be included to improve freight movement by extending the southern end of State Route 509. A four-lane road would be built from South 188th Street in Burien to South 210th Street in SeaTac, where it would connect to Interstate 5.

New lanes also would be added to I-5, from the Kent-Des Moines Road to 320th Street in Federal Way.

A new South Park Bridge, heavily used by Southwest King County commuters, is included because the existing span is so deficient it's scheduled to be closed in three years if no funding comes available to replace it.

A new parallel bascule drawbridge is planned at a cost of $99 million.

The roads projects will join bus and light-rail projects being proposed to voters by Sound Transit.

The Regional Transportation Investment District Planning Committee was created by the Washington Legislature to keep people and commerce moving through the most dense parts of King, Snohomish and Pierce counties.

It's supposed to focus on the most congested highways and bridges in the three-county area and either add to or finish work on state highway projects.

Projects recommended by the Regional Transportation Investment District are designed to affordably improve traffic flow, safety and "performance," according to the agency's website.

Its projects also integrate roads and transit projects that benefit the most people.

The county councils of King, Pierce and Snohomish counties must each approve the final list of projects before it goes to the voters.

County approval seems likely because the members of the three county councils also comprise the Regional Transportation Investment District Planning Committee, which is proposing the package of construction projects.

The Regional Transportation Investment District Planning Committee approved the voter package on a 19-2 vote, so county approval seems likely.

It will be up to voters living in the three counties to decide in November whether to tax themselves to pay for the approximately $4 billion in regional transportation investments.

The money would be combined with King County's Transit Now program and the city of Seattle's Bridging the Gap campaign, both of which were approved by voters last fall.

Tim St. Clair can be reached at timstc@robinsonnews.com or 932-0300.