Washington State Route 18

Washington State Route 18

State Route 18, also known as SR 18 or Highway 18, is a 28-mile-long (45 km) state highway in the U.S. state of Washington, which connects State Route 99 in south King County with Interstate 90. It runs northeast from Federal Way, through Auburn, south Kent, Covington, Maple Valley, over the 1,375-foot (419 m) Tiger Summit, and then terminates at I-90 about 8 miles (13 km) east of Issaquah near Snoqualmie. This highway is the most direct route between Eastern Washington and Tacoma. North of I-90, Highway 18 becomes a local arterial, Snoqualmie Parkway. Snoqualmie Parkway continues to SR 202 just east of Snoqualmie Falls. This is the shortest route between I-90 and attractions at Snoqualmie Falls.

Highway 18 is a dangerous roadway due in part to the heavy truck traffic between I-5 and I-90. For the past several years, work has been done on a project to turn SR 18 into a limited access highway and widen it to four lanes, two in each direction. Three-fourths of the highway upgrade has been completed; it now has four lanes from Federal Way to Issaquah Hobart Road. The last one-fourth of the expansion is 7 miles (11 km) which includes the climb up to Tiger Summit and the last 2 miles (3.2 km) to Interstate 90 with a freeway-to-freeway connection. The project still needs $267.5 million in funding and construction is set to be completed by 2015.

SR 18 forms part of one possible route for a proposed future Interstate 605, though the idea faces considerable opposition. However, some argue for renumbering the highway as an Interstate highway after completion of the widening, since it links Interstate 5 to Interstate 90.