Interstate 505 California

Interstate 505 California

Overview

I-505 California Map

Interstate 505 in California connects I-80 in Vacaville with I-5 near Dunnigan. Generally rural, the freeway provides part of a long distance route linking the San Francisco Bay area with the Pacific Northwest. North from industrial park areas of Vacaville, I-505 stays east of the English Hills through a mix of ranch and agricultural areas to the outskirts of Winters, a city of around 7,000. Beyond there, the route bee lines north to SR 16 near the community of Madison, where sunflowers grace the area landscape, providing a truly magnificent site during the peak flowering period.

Crossing Cache Creek, Interstate 505 makes a gradual shift to the east, traversing farm land east of Hungry Hollow into the Dunnigan Hills. Emerging from the hills at Oat Creek, the final segment ties into I-5 amid agricultural land in northern Yolo County.

History

I-505 is unusual for a California Interstate in that it was not predated by a U.S. highway or state route, as most others in the state were. It was included as part of Interstate 5W until 1964. The planned route for I-5W would have followed:

  • Interstate 580 west from I-5 near Vernalis to Hayward
  • Interstate 580 northwest from Hayward to Oakland
  • Interstate 80 northeast from Oakland to Vacaville
  • Interstate 505 north from Vacaville to Zamora
I-5W - 1963 Map

The proposed route of Interstate 5W in 1963.

Route Information

  • North End – Dunnigan, CA

  • South End – Vacaville, CA

  • Mileage – 32.98

  • Cities – Vacaville

  • Junctions – I-80 I-5

Source: December 31, 2021 Interstate Route Log and Finders List

I-505 Annual Average Daily Traffic (AADT)

Source: Caltrans 2017 Traffic Volumes : Route 505-980

I-505 - 1967 Map
Interstate 505 in 1968

Interstate 505 was initially built as a two lane road, with two freeway sections: two miles outside Winters, with an interchange at SR 128, and one mile at the interchange with SR 16 near Madison.1

Like the eastern end of Interstate 580, the northern end of I-505 is located in a sparsely populated area in the Central Valley. Traffic counts along the route are some of the lowest of any California Interstate, with just 10,700 vehicles per day (vpd) recorded by Caltrans at the north end in 2015. Completion of the SR 113 freeway between I-80 at Davis and I-5 at Woodland in 1990 may have deferred some of the I-505 traffic headed to communities northeast of Vacaville along Interstate 80.

Interstate 505 was signed as Temporary I-505 between Vacaville to Dunnigan until 1972. The route consisted of a two lane road prior to that time, with two short freeway segments serving interchanges with SR 16 and SR 128. Staged construction through 1978 upgraded the remainder of I-505 to freeway standards. Completed first was the section from SR 16 to SR 128, followed by I-5 south to SR 16, and SR 128 south to I-80.1

Mid-State Tollroad

The state of California entered a franchise agreement with the California Toll Road Company (CTRC) to develop the Mid-State Tollroad along the planned SR 84 and SR 239 corridors between I-680 at Sunol and SR 4 at Antioch. This included a connection to the I-580 / 205 interchange near Tracy via future SR 239. An extension of the toll road included a northern segment into the Sacramento / San Joaquin River Delta.2

Had this extension been constructed, potential corridors included possible connections with the south end of Interstate 505, the freeway along SR 113 near Davis, or a route along SR 84 toward Sacramento. However due to environmental concerns north of Antioch, costs of bridges spanning the San Joaquin and Sacramento Rivers, and political opposition, none of these proposals came to fruition.3 Caltrans eventually deleted portions of the project, including the extension north to Solano County, in 1993.2

The rest of the proposed toll road remained in question, having been suspended due to political considerations. The project web site referenced a $600 million, 40 mile or more four lane toll road running northeast from I-680 near Sunol to SR 4 near Antioch.2

Photo Guides

North End I-5 – near Dunnigan, California

I-505 North at I-5

I-505 north connects with I-5 ahead of Dunnigan, CA

The north end of Interstate 505 ties into I-5 ahead of two exits for the census designated place of Dunnigan. 07/15/23

I-505 north at the wye interchange with I-5

Interstate 505 leaves the Dunnigan Hills and converges with I-5 north across an open agricultural area east of Bird Creek. A lone shield assembly acknowledges the forthcoming junction. 07/15/23

The north end of Interstate 505

Forming an auxiliary lane to the diamond interchange (Exit 554) with Road 8, a sweeping ramp joins Interstate 5 north from the end of I-505. 07/15/23

I-5 South at I-505

I-5 south at I-505 - Dunnigan, CA

Road 8 spans Interstate 5, one mile north of the wye interchange (Exit 553) with I-505 south. 07/11/18

I-5 south at I-505 - Dunnigan, CA

Interstate 505 branches nearly south from I-5 ahead of the Dunnigan Hills. Interstate 5 remains along a southeasterly course to Zamora, Dufour and Yolo. 07/11/18

Throwback – I-5 South at I-505

I-5 south at I-505 - 2006
I-5 south at I-505 - 2006

Button copy signs for Interstate 505 leading south to Winters and Vacaville were replaced by 2012. 05/29/06

South End I-80 – Vacaville, California

I-505 South at I-80

I-505 south at I-80 - Vacaville, CA

The first sign for Interstate 80 appears within the diamond interchange (Exit 1C) joining I-505 with Vaca Valley Parkway. 07/11/18

I-505 south at I-80 - Vacaville, CA

The mainline of I-505 defaults onto Interstate 80 west toward Oakland and San Francisco. 07/11/18

I-505 south at I-80 - Vacaville, CA

Exit 1B connects I-505 with not only Interstate 80 east to Sacramento, but also County Airport Road at parallel Monte Vista Avenue. 07/11/18

I-505 south at I-80 - Vacaville, CA

I-505 south converges with westbound I-80 along a commercial strip leading southwest through Vacaville. Exit 1 B loops onto I-80 east ahead of Dixon. 07/11/18

I-80 East at I-505

I-80 one and a half miles ahead of I-505 north in Vacaville, CA

Interchange sequence sign posted 1.5 miles ahead of I-505 along I-80 east at the Elmira Road underpass. I-505 provides a cutoff from I-80 east to I-5 north for Red Bluff, Redding and Portland Oregon. 07/15/23

Button copy sign posted a half mile from I-505 on I-80 east.

With an adjacent array of big box retail and the Vacaville Premium Outlets adjacent to the freeway, the commercialized stretch of I-80 advances east from the Allison Drive entrance ramp to Exit 56 for I-505 north. 07/15/23

I-80 east meets I-505 adjacent to Orange Dr and the Vacaville Premium Outlets.

Exit 56 departs with two lanes for I-505 from I-80 east at the Nut Tree Road overpass. I-505 branches northward by Nut Tree Airport (VCB) and several distributor centers and warehouses to Exit 3 at Midway Road. 07/15/23

Two lanes separate from I-80 east for I-505 north in Vacaville, CA.

An auxiliary lane extends east from Allison Drive to the modified trumpet interchange (Exit 56) with Interstate 505 north to Winters. 07/15/23

I-80 West at I-505

I-80 west at I-505 - Vacaville, CA

Interstate 80 angles southwest through Vacaville to meet I-505 one mile west of Leisure Town Road. Vaca Valley Road replaced a portion of Leisure Town Road, with it constructed as a new arterial leading west to I-505 at Exit 1. 07/02/13

I-80 west at I-505 - Vacaville, CA

Orange Drive parallels the south side of I-80 as a commercial frontage road to the exchange (Exit 56) with Interstate 505. Areas to the north fall within the 172 acre Vaca Valley Business Park development.3 07/02/13

I-80 west at I-505 - Vacaville, CA

Winters lies 11 miles to the north along Interstate 505. Signs for I-505 on I-80 west only reference the continuation of I-5 north to Redding beyond the freeway end. 07/02/13

I-80 west at I-505 - Vacaville, CA

The final button copy sign for I-505 on Interstate 80 west was replaced by 2016. Interstate 505 initially travels north between Nut Tree Airport (VCB) and Vaca Valley Business Park to Vaca Valley Parkway. 07/02/13

South End Throwback

I-80 East at I-505

I-80 east at I-505 - 2009

Interstate 80 east spans Mason Street / Elmira Road ahead of Ulatis Creek and Exit 55 to Nut Tree Parkway. Replaced by 2016, this interchange sequence sign was the first reference of I-505. 07/18/09

I-80 east at I-505 - 1976

I-80 used to overtake Monte Vista Avenue at a parclo interchange one half mile west of I-505. Monte Vista Avenue is the historic alignment of U.S. 40, and per USGS topos it was already replaced by a four lane bypass for U.S. 40 by 1953. This bypass is now I-80, and the former ramps pictured here were replaced with a new interchange for Allison Drive. Photo by Michael Summa (1976).

I-80 east at I-505 - 2009

Button copy signs preceding the separation of I-505 north from I-80 east here were replaced by 2016. 07/18/09

I-80 east at I-505 - 2009

The first exit number sign for I-505 on I-80 east replaced this assembly by 2007. The exchange joining the two freeways is the same design at the junction of I-86/390 in the Southern Tier of New York, with a U-turn ramp joining I-505 south with I-80 east. 03/31/05

I-80 West at I-505

I-80 west at I-505 - 2003

Former ground level sign posted one mile ahead of the modified trumpet interchange with I-505 north on I-80 west. The parclo B4 interchange (Exit 57) with Leisure Town Road was both modernized and expanded with two additional ramps. A new entrance ramp joins I-80 west at this scene now. 08/23/03

I-80 west at I-505 - 2003

One quarter mile ahead of Exit 56 for I-505 north on Interstate 80 west. 08/23/03

Sources:

  1. California Highways (www.cahighways.org): Route 505.
  2. Mid-State Tollway. http://www.dot.ca.gov/hq/ paffairs/about/toll/midstate.htm California Department of Transportation (Caltrans), project web site.
  3. Rouse, Joe.
  4. http://www.kearny.com/pdf/Vaca_Valley_Business_Center.pdf.

Page updated October 4, 2023.