Facilities for pedestrians, equestrians, or bicyclists shall be incorporated into the design of highways and freeways along corridors where such facilities do not exist upon a finding that such facilities would be of joint use and conform to the comprehensive plans of public agencies for the development of such facilities, will not duplicate existing or proposed routes, and that safety to both motorists and to pedestrians, equestrians, and bicyclists would be enhanced by the segregation of traffic.
In planning and design of all highways, every effort shall be made consistent with safety to promote joint usage of rights-of-way for trails and paths in accordance with the comprehensive plans of public agencies.
RCW 47.30.020