The entirety of I-505 is defined in section 617 of the
California Streets and Highways Code as
Route 505, and that the highway is from "
Route 80 near
Vacaville to
Route 5 near
Dunnigan". This definition roughly corresponds with the
Federal Highway Administration (FHWA)'s route logs of I-505. The southern terminus of I-505 is at I-80 next to the
Nut Tree Airport in the
Nut Tree area in
Vacaville. From there, it travels north about through rural areas near the western edge of the
Sacramento Valley before reaching
Winters. I-505 then skirts the eastern
city limits of Winters, intersecting with
State Route 128—the only exit in Winters. After leaving that city, the Interstate then proceeds north through rural areas again for about , including an interchange with
California State Route 16 near
Madison, until it reaches its northern terminus with I-5 near
Dunnigan. For its entire length, I-505 is a four-lane freeway (two lanes in each direction) with a maximum speed limit of , which is typical for rural Interstates in California. I-505 is part of the
California Freeway and Expressway System, and is part of the
National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the
Federal Highway Administration. ==History==