Cartoon by Frank Shiers

Improvements coming to State Route 18 after a three decades-long effort to widen the entire state highway.

The state passed its nearly $17 billion Move Ahead Washington Transportation Package earlier this month, which earmarked $640 million in funds to widen and add safety improvements to a five-mile stretch of SR 18 near Tiger Mountain — the last section in need of construction funding.

Alongside construction at the SR-18/ I-90 interchange — which is expected to begin later this year — the remaining two-lane portion of the road will be expanded to four lanes with 10-foot sholders on both sides. Construction at the intersection should finish by 2025, according to the state Department of Transportation.

Although construction and subsequent road closures along SR 18 will have its own challenges and delays, clearing the funding barrier represents a huge milestone.

Known as one of the deadliest roads in King County, safety improvements along the highway began in the 1990s as officials worked to widen the entire highway from two to four lanes.