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Interstate 380

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This past weekend I drove over twenty Californian highways with a good chunk of them being around the San Francisco Bay Area.   The first highway I attempted was Interstate 380 from San Francisco International Airport west to I-280.


I-380 is an approximately 1.7 mile freeway connecting from US 101 at San Francisco International Airport west to I-280.  The entire routing of I-380 is within San Mateo County and despite it's small size was conceived as a much larger route.

According to CAhighways.org the path of I-380 was first conceived as Legislative Route Number 229 in 1947 between US 101 Bypass west to US 101 in San Bruno.

CAhighways.org on LRN 229

LRN 229 was extended to CA 1 Pacifica in 1959 by the Legislature.  While LRN 229 in it's original form was too small display on State Highway Maps it does appear in full scope by the 1960 addition.

1960 State Highway Map

During the 1964 State Highway renumbering LRN 229 was reassigned as LRN 186 which is reflective on the State Highway Map of the same year.

1964 State Highway Map

According to CAhighways.org the path of LRN 186 was authorized to be built as part of the Interstate system in 1968.  By 1969 the route of I-380 was defined by the Legislature and it's implied path appears on the 1970 State Highway Map .

1970 State Highway Map 

I-380 is shown as mostly complete between US 101 and I-280 on the 1975 State Highway Map.  There appears to be a small gap over the rails between CA 82 (former US 101) and US 101 on the Bayshore Freeway (former US 101 Bypass).

1975 State Highway Map

On the 1977 State Highway Map I-380 is shown fully completed between I-280 and US 101.

1977 State Highway Map

The extension of I-380 west to CA 1 in Pacifica would be cancelled by 1979 according to CAhighways.org.

CAhighways.org on Interstate 380

Interestingly I-380 has been the subject of several proposals for a new bridge across San Francisco Bay with the latest popping up in 2017.  Most of the modern proposals would have the new crossing connecting with I-238 which would in theory remove the Interstate numbering violation.  CAhighways.org summaries the I-380 extension proposals on the above link.

My approach to I-380 was from US 101 northbound at San Francisco International Airport.






As I approached the westbound ramp for I-380 there was a small but strong storm overhead.  While my photos didn't turn out all that great given the strong rains I was able to get some "acceptable" enough samples to convey the route.  As I-380 ascends over US 101 it enters the City of San Bruno.




I-380 westbound meets CA 82 approximately in the middle of it's routing.  CA 82 is the historic route of the El Camino Real and original alignment of US 101 before the Bayshore Freeway was built.



I-380 westbound terminates at I-280.  Traffic is given the option of heading both northbound and southbound on I-280.



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Unknown said…
The next time you are in the area, you might want to approach I-380 from southbound 280. As you follow that ramp you will see an "overpass to nowhere" which apparently was meant to be the first piece of the planned westward extension over the hills to Pacifica.
2:43 PM
Jonathan - Beaver State Roads said…
I noticed that the exits on I-380 are numbered 5 for CA-82, but then 5A and 5B for I-280. Do you have any idea for the numbering discrepancy? Shouldn't the CA-82 exit have been numbered 5C, or I-280 4A and 4B?
4:14 AM
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