[3][4] In 1998, the Washington State Legislature ordered a $500,000 study to investigate the benefits of extending SR 18 north to Everett through the Snoqualmie Valley.

[2] In 2002, Bellevue Square owner Kemper Freeman, Jr. made his support known for a new freeway linking Snohomish County via the Snoqualmie Valley.

[7] Another $500,000 study was ordered in 2003 by the legislature, creating a new commerce corridor to link Lewis County in the south to the Canada–US border in the north.

WSDOT has widened most of SR 18 between I-5 and Hobart to full freeway standards, while the remainder is a two-lane mountainous highway with truck lanes on uphill segments.

WSDOT once proposed to creating a full limited-access freeway for the remainder,[9] but updated preliminary plans would upgrade it to a four-lane divided highway, with right-in/right-out at Tiger Mountain and a diverging diamond interchange at I-90.