WSDOT is planning to widen the remaining section of SR 18, between Issaquah-Hobart Road south of Tiger Mountain to I-90 near Snoqualmie to serve capacity to at least 2035, but funding has not been approved for the project. The project will widen the highway to four general purpose lanes with a truck lane on lanes traveling uphill towards the summit of Tiger Mountain and using a median barrier to separate opposing lanes of traffic and prevent head-on collisions. New interchanges are planned for the entrance of Tiger Mountain State Forest and I-90, to be completed after 2023. The original design for the I-90 interchange included flyover ramps and a double roundabout, but a revised design option will consider a diverging diamond interchange.