Where an existing highway severs, or where the right-of-way of an existing highway accommodates a trail for pedestrians, equestrians, or bicyclists or where the separation of motor vehicle traffic from pedestrians, equestrians, or bicyclists will materially increase the motor vehicle safety, the provision of facilities for pedestrians, equestrians, or bicyclists which are a part of a comprehensive trail plan adopted by federal, state, or local governmental authority having jurisdiction over the trail is hereby authorized. The department of transportation, or the county or city having jurisdiction over the highway, road, or street, or facility is further authorized to expend reasonable amounts out of the funds made available to them, according to the provisions of RCW
46.68.090, as necessary for the planning, accommodation, establishment, and maintenance of such facilities.