Major suburban development in the Mill Creek area began in the 1970s and contributed to growing traffic congestion on SR 527, leading eventually to development moratoriums as temporary measures to quell growth. The northernmost section of the highway, in Everett between 112th Street and the Broadway Interchange, was expanded to five lanes in the late 1970s using city funding, while the rest remained two lanes wide. In 1980, the state department of transportation began preliminary planning for a wide-scale project to widen the highway to five lanes (including a center turn lane and sidewalks) in 1980. The state legislature funded the widening project in 1990 with proceeds from a statewide gas tax increase, which coincided with the end of the development moratorium.