Interstate 505 in California connects Interstate 80 in Vacaville with Interstate 5 near Dunnigan. This freeway was at one time planned to be part of Interstate 5W, and it provides southbound travelers on Interstate 5 a fast connection to the San Francisco Bay Area. Similarly, drivers heading northeast out of the Bay Area may also use this highway to go to the Pacific Northwest via the fast Interstate 5. The only town of note along Interstate 505 is Winters, near the junction with California 128. In the farmland along Interstate 505 near California 16, travelers may see acres of sunflowers, a truly magnificent site during the peak flowering period.
Interstate 505 is unusual for a California Interstate in that it was not pre-dated by a U.S. or state route. Most other California Interstates today replaced an existing U.S. or state highway. In addition, Interstate 505 has the lowest average daily traffic counts of any California Interstate. While the counts may not seem low by other states' standards, it is low for such a major connector between Interstates 5 and 80. Notably, with the construction and recent completion of the California 113 freeway between Interstates 5 and 80 between Woodland and Davis, some traffic has deferred to that route to reach communities northeast of Vacaville along Interstate 80.
Interstate 5W was planned in 1964 as an alternate for Interstate 5 travelers planning to visit the Bay Area. It would have followed (from north to south): Interstate 505 from Zamora south to Vacaville; Interstate 80 from Vacaville southwest to Oakland; Interstate 580 southeast from Oakland to Hayward; and Interstate 580 east from Hayward to near Vernalis. Like the eastern end of Interstate 580, the northern end of Interstate 505 is located in a sparsely populated area in the Central Valley.
In 1993, the state of California planned the Mid-State Tollroad along the future California 84 and California 239 corridors between Interstate 680 at Sunol and State Route 4 at Antioch, with a connection to the Interstate 580/205 interchange near Tracy via future California 239. At one time, this toll road was planned to extend further north, into the Sacramento/San Joaquin River Delta. If this extension were constructed, possible corridors included a connection to the southern terminus of Interstate 505, the southern terminus of the California 113 freeway near Davis, or a routing along California 84 toward Sacramento. However, none of these connections will be constructed due to environmental concerns and political opposition. The remainder of the proposed toll road is also in question, as the project has been suspended due to political considerations.
Regarding the Mid-State Toll Road, Joe Rouse, the toll road would run "down the built and unbuilt alignments of California 84 between Sunol and Antioch. It could easily be signed California 84. A spur would be provided to the Interstate 205/Interstate 580 interchange near Tracy, following unbuilt California 239. The original plan called for it to extend north of Antioch, which would require large, expensive bridges across the San Joaquin and Sacramento Rivers. The tollway would have connected with Interstate 80 between Vacaville and Dixon, with a spur connecting to the Interstate 505/Interstate 80 interchange in Vacaville. The segment north of Antioch was killed due to environmental and cost concerns."
Eastbound Interstate 80 approaching northbound Interstate 505 in Vacaville, one half mile west of the split. Photo taken 10/00.
Original Interstate 505 button copy overhead, one-half mile south of the southern terminus. This is now Exit 56 with California's exit numbering project. Photo taken by Michael Summa (1976).
Perspective from Interstate 80 east
Westbound Interstate 80 approaching Junction Northbound Interstate 505, one mile. Interstate 505 leads north to Winters and Dunnigan, where it meets Interstate 5. Interstate 5 connects to Redding and points north. Photo taken 08/23/03.
Westbound Interstate 80 approaching Junction Northbound Interstate 505, next right. Photo taken 08/23/03.
Westbound Interstate 80 at Junction Northbound Interstate 505. Interstate 5 connects to Redding and points north. Photo taken 08/23/03.
Perspective from Interstate 505 north
Northbound Interstate 505 as it exits from Interstate 80. There is a freeway entrance along the transition from Interstate 80 eastbound to Interstate 505 northbound, as shown in the next photo. Photo taken 10/00.
Perspective from Vacaville Factory Outlets
The Vacaville Factory Outlet Stores loom large at the southern end of Interstate 505 in Vacaville. This freeway entrance to northbound Interstate 505 is actually located on the transition ramp from eastbound Interstate 80 to northbound Interstate 505 (before the transition ramp passes over the lanes of Interstate 80). This marks the furthest south point along Interstate 505, and makes leaving the factory outlet stores very easy. Photo taken 10/00.
Northern Terminus - Interstate 5 - near Dunnigan, California
Northbound Interstate 505 approaching the northern end at Junction Interstate 5. Note the use of a trailblazer assembly for Junction North Interstate 5. There is no direct access from Interstate 505 northbound to Interstate 5 southbound, and vice versa. Photo taken by Joe Rouse, 10/00.
Southbound Interstate 5 approaching Junction Southbound Interstate 505. Note the destination city of Winters and the control city of San Francisco. There is not much development in and around Zamora/Dunnigan, as evidenced by this photo. Photo taken by Joe Rouse, 10/00.