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Interstate 405; Carmageddon on the San Diego Freeway and legacy of the first California State Route 7

Recently while in the Los Angeles Area I drive the entirety of Interstate 405 which is otherwise known as the San Diego Freeway.


Interstate 405 is a 72 mile auxiliary spur of Interstate 5.  I-405 is a north/south freeway which begins at I-5 near San Fernando in Los Angeles County and ends at I-5 in Irvine of Orange County.  I-405 is one of the more infamous freeways in California due to it carrying some of the busiest freeway segments in the entirety of the United States.  The segment of I-405 between Exit 21 and Exit 22 in Seal Beach is the busiest stretch of freeway in the United States with an annual average daily traffic count of almost 400,000 vehicles.

I-405 has a reputation for being a commuting nightmare and probably is responsible for much of the urban sprawl of west of downtown Los Angeles.  I-405 is typically referred to as "the Four-oh-Five" and has inspired terminology such "Carmageddon" or "Carpocalypse."  I-405 has surprisingly humble roots as part of Sepulveda Boulevard and the original California State Route 7.

The direct predecessor route to I-405 is the first CA 7 and Legislative Route Number 158.  LRN 158 in it's original configuration was routed entirely on Sepulveda Boulevard between San Fernando southward to west Los Angeles.  Construction of Sepulveda Boulevard by Los Angeles County began in the late 1920s.  The route of Sepulveda Boulevard was aligned through Sepulveda Canyon/Pass of the Santa Monica Moountains.  Construction of Sepulveda Boulevard through Sepulveda Pass began in 1929 and by the following year the Sepulveda Boulevard Tunnel opened to traffic.

For reference the Sepulveda Boulevard Tunnel is pictured below facing northbound.


The article below shows early construction of Sepulveda Boulevard in Sepulveda Pass.

Lost Los Angeles; How Sepulveda Canyon became the 405

In 1933 Sepulveda Boulevard between US 99/LRN 4 in San Fernando south to LRN 60 near Mines Field (future L.A.X.) was added to the State Highway system as LRN 158.

CAhighways.org on LRN 158 

By 1934 the Signed State Highway system was created and the majority of LRN 158 on Sepulveda Boulevard was added to the first CA 7.  CA 7 in full scope was intended to be one of the largest State Highways.  The original CA 7 had a southern terminus at CA 3/LRN 60 in Torrence and a north terminus at the Oregon State Line in Modoc County.  The maps below from a 1934 Department of Public Works publication shows the full extent of the original CA 7.

Below is a snipped image from the directory of Signed State Highways announced in 1934.  The full extent of CA 7 is described below:


The route of the first CA 7 in 1934 was as follows headed northbound from CA 3 in Torrence:

-  LRN 164 to LRN 158 in West Los Angeles.
-  LRN 158 in West Angeles to US 99/LRN 4 in San Fernando.  LRN 158 originally connected Sepulveda Boulevard to San Fernando Boulevard (LRN 4) via Brand Boulevard.
-  LRN 23 in San Fernando along the eastern flank of the Sierras to LRN 95 near Coleville.
-  LRN 95 from Coleville to the Nevada State Line.
-  CA 7 had a route gap through Nevada and resumed north of Reno on LRN 29.  CA 7 followed LRN 29 to CA 36 near Susanville.
-  LRN 73 from CA 36 north to the Oregon State Line.

The images below are from the same 1934 Department of Public Works guide showing the full route of CA 7.




The 1934 Department of Public Works guide cited above can be read online below.

1934 California Highway and Public Works Guide

More detail on the legislative detail of the LRNs that comprised the original CA 7 can be found on CAhighways.org.

CAhighways.org on CA 7

Numerous changes occurred to the State Highway system following the creation of the Signed State Routes of the course of the remainder of the 1930s.  The following changes occurred regarding the first CA 7 from 1934 to 1938:

-  CA 3 was reassigned as US 101A in 1934.
-  Either in 1934 or 1935 US 395 was extended into California.  US 395 was routed along what was CA 7 from near Inyokern north to the Oregon State Line.  CA 7 was subsequently truncated to US 395 near Inyokern.
-  In 1937 US 6 was extended into California.  US 6 absorbed the route of CA 7 from San Fernando north to US 395 near Inyokern.  CA 7 was subsequently truncated to US 99 in San Fernando.
-  Likely in 1938 CA 7 was truncated to West Los Angeles to US 101A via the remainder of LRN 158 on Sepulveda Boulevard.  What was CA 7 between West Los Angeles and Torrence on Centinela Avenue/La Brea Avenue/Hawthorne Avenue became CA 107 which is first seen on the 1938 State Highway City Insert.


The first plan for a "San Diego Freeway" was drafted by the Engineering Bureau Department of Public Works of the City of Los Angeles in 1939 according to CAhighways.org.  By 1947 the legislative definition of LRN 158 was extended to Long Beach to the planned LRN 167 (modern I-710 on the Long Beach Freeway).  The extension of LRN 158 to Long Beach can be seen on the 1948 State Highway Map City Insert.


In 1951 LRN 158 was extended east of LRN 167 to LRN 2 in El Toro to the planned US 101 Santa Ana Freeway.  At this point the basic planned form of what would become the San Diego Freeway took shape.  The extension of LRN 158 to LRN 2 can be seen on the 1952 State Highway Map City Insert.


According to CAhighways.org work on what was then known as the "Sepulveda Freeway" in late 1953 in the Sepulveda Canyon Area of West Los Angeles.  The Sepulveda Freeway began being known as the "San Diego Freeway" in official documents by 1955.  The San Diego Freeway and route CA 7/LRN 158 was selected as a chargeable Interstate in 1955.  Some of the early proposals for the route number designation of the San Diego Freeway were I-9 and I-3 before I-405 was selected.  By 1957 the first segment of the San Diego Freeway opened in Culver City north to the Santa Monica Mountains as CA 7.  Apparently the CA 7 signage would be replaced in the summer in 1958 with I-405 shields

CAhighways.org on I-405

On the 1959 State Highway Map City Insert the planned route of I-405 through Sepulveda Pass bypassing the Sepulveda Boulevard Tunnel appears.


The planned route of I-405 between US 101 north to US 99 appears on the 1961 State Highway Map.


I-405 in Sepulveda Pass is shown complete by 1963.  I-405 is also shown completed between CA 107/LRN 164 east to CA 15/LRN 164.



In 1964 the California Highway Renumbering occurred.  CA 7 is shifted off it's original corridor eastward onto what was CA 15/LRN 167 (future I-710).  I-405 is shown fully completed between I-5 and the new CA 7.



The 1965 State Highway Map City Insert shows I-405 nearly completed to the future I-605.


The 1966 State Highway Map City Insert shows I-405 completed to CA 39.


The 1967 State Highway Map City Insert shows I-405 completed close to the junction of CA 55/CA 73.  CA 107 is truncated off of Centinela Avenue, La Brea Avenue and Hawthorne Avenue to I-405 in Lawndale. 


The 1969 State Highway Map shows I-405 completed to I-5 in Irvine.  The full route of the San Diego Freeway is open to traffic.


On a side note CA 107 was recently truncated to the southern City Limit of Lawndale in 2008.  CA 107 exists solely on Hawthorne Bouelvard south of Lawndale to CA 1 in Walteria. While there is no active plans to relinquish the remainder of CA 107 it would seem the highway is likely endangered.  CA 107 remains the only segment of State Highway with a clear connection to the signed route of the first CA 7. 


So with the history of I-405 above in mind, the question is how does a Interstate with segments nearly reaching 400,000 cars a day function?   My personal answer would be; surprising well as a through route and not so much as a commuter route.  My opinion may have been skewed by the fact that I drove the entirety of the Kennedy Expressway in Chicago several times less than a month prior to driving the entirety of I-405.  I personally would consider the Kennedy Expressway which carries parts of I-90 and I-94 to be beyond anything else that I've driven in the United States for large scale traffic jams.  That said, according to a study in 2015 I-405 had three of the top thirty worst bottleneck points for traffic in the United States:


The sections of I-405 cited in the article above by national ranking for traffic bottlenecks is as follows:

Number 2:  I-405 between CA 22 and I-605 in Seal Beach.  
Number 4:  I-405 between Venice Boulevard and Wilshire Boulevard.
Number 29:  I-405 between Burbank Boulevard and Ventura Boulevard. 

Probably the most amusing aspect to my drive on the entirety of I-405 was that it was on a week day and it didn't involve stopping for a traffic jam once.  I have never in any previous attempts been able to drive the entirety of I-405 at any day light hour without at least stopping once.  Considering I managed to pull off a full clinch of I-405 on a weekday mid-morning without stopping is incredibly lucky.

My approach to I-405 was on southbound I-5 in the northern City Limits of Los Angeles near San Fernando.  I-405 begins shortly south of the west terminus of I-210 on the route of I-5.  My direction on travel on I-405 was southbound towards Irvine. 






Immediately as I turned off I-5 south onto I-405 south I was greeted with a "I-405; San Diego Freeway" sign.  The "San Diego Freeway" name of I-405 is largely assumed to have been put in place to encourage through traffic to use it as a bypass of I-5 through downtown Los Angeles.  


I-405 south skirts just to the west of Mission San Fernando Rey de Espana which was established in 1797.  The most northern extent of I-405 closely follows the historic alignments of; El Camino Real, El Camino Viejo and the Stockton Los Angeles Road.  El Camino Real continued west along the coast following the Spanish Missions while both El Camino Viejo and the Stockton Los Angeles Road continued north towards Newhall Pass.  I-405 south bisects part of Sepulveda Boulevard which were part of later alignments CA 7. 

I-405 north does not include a ramp I-5 south.  The defacto access to I-5 south from I-405 north is via CA 118 on the Simi Valley Freeway.  I-405 south encounters CA 118 at Exit 71. 






I-405 south continues through San Fernando Valley and intersects US 101 on the Ventura Freeway.  Sepulveda Boulevard runs to the east of I-405 southward through San Fernando Valley towards Sepulveda Canyon. 








Immediately south of the US 101/Ventura Freeway I-405 south has a junction with the former surface alignment of US 101 on Ventura Boulevard.  


I-405 south crosses over Sepulveda Boulevard approaching Sepulveda Canyon.  Sepulveda Boulevard follows I-405 to the west of the freeway, there is an access point from Exit 63A. 



My cover photo for this blog was near the Sepulveda Boulevard Exit on I-405 south.  It is hard to imagine that about a century ago what is essentially now a miss-mash of cars and concrete was just a mountain wilderness.


At Exit 61 I-405 south meets Mulholland Drive and passes underneath the 2013 Mulholland Drive Bridge.  






The 2013 Mulholland Drive bridge was the instigator for what became known as "Carmageddon I and Carmageddon II."  Both Carmageddon I and II involved the demolition of sections of the 1960 Mulholland Drive Bridge which required closing much of I-405 in Sepulveda Canyon.  Carmageddon I took place over the weekend of July 15th of 2011 whereas Carmageddon II took place over the weekend of September 28th of 2012.  By December of 2013 the new Mulholland Drive Bridge reopened to traffic. 


Mulholland Drive opened in 1924 from Cahuenga Pass in Hollywood westward over Sepulveda Pass and was originally known as "Mulholland Highway."  Whereas Sepulveda Boulevard dipped under Mulholland Drive via the 1930 Sepulveda Boulevard Tunnel the future San Diego Freeway required it be moved to an overpass.  The first Mulholland Drive Bridge was completed by 1960 and the article below describes in greater detail the history of the structure. 


This map of the Los Angeles Road Network in 1938 shows the original crossing of Mulholland Drive through Sepulveda Pass.  I marked the future location of the 1960 Mulholland Drive Bridge. 


I-405 south continues through Sepulveda Canyon before emerging into West Los Angeles near Exit 57 for Sunset Boulevard.  I-405 again crosses over Sepulveda Boulevard which shifts to the east side of the freeway.











At Exit 55 B/C I-405 accesses Wilshire Boulevard. 






To the east on Wilshire Boulevard is the La Brea Tar Pits which I visited back in 2013. 


At Exit 55A I-405 south accesses former US Route 66 and CA 2 at Santa Monica Boulevard.  CA 2 is gradually being relinquished and as of 2010 the route no longer exists on Santa Monica Boulevard east of I-405 to US 101. 




At Exit 53 I-405 south intersects I-10.  At Exit 54 I-405 south meets the original CA 26 at Olympic Boulevard/Pico Boulevard.





At the limits of Culver City I-405 south meets the unsigned CA 187 on Venice Boulevard. 








I-405 re-renters West Los Angeles and meets CA 90 at Exit 50B. 






I-405 south crosses over Sepulveda Boulevard one final time at Exit 49.  The original shift of CA 7 onto Centinela Avenue is located near Exit 49.



Traffic on I-405 south to LAX is directed to take Exit 46 onto Century Boulevard.  Access to I-105 is signed from Exit 45.











I-405 south passes through Del Aire and Hawthorne before meeting CA 107 at Exit 42A.  As noted above CA 107 south of I-405 on Hawthorne Avenue is a remaining segment of the original CA 7. 





I-405 south enters the City of Torrence, CA 91 is signed from Exit 40A on Artesia Boulevard.  CA 91 now ends at I-110 and was previously CA 14 before the California Highway Renumbering. 



At Exit 38B I-405 south has an access point on the eastern City Limit of Torrence for CA 213 on Western Avenue and the unbuilt CA 258.  CA 213 utilizes Western Avenue south of I-405 whereas CA 258 has a proposed alignment north of it. 

As I-405 south enters Carson it has a junction with I-110 (former CA 11 and US 6).




I-405 south in Carson has a truck weigh station. 


At Alameda Street in Carson I-405 south meets the proposed alignment of CA 47 which was ultimately never built.  





I-405 south enters Long Beach and meets I-710. 




I-405 south briefly enters Signal Hill before re-entering Long Beach.  At Exit 27/Lakewood Boulevard I-405 south meets CA 19.  CA 19 is signed as access to Long Beach Airport.






I-405 south meets I-605 north at Exit 24A.  Underneath the I-405/I-605 interchange is the Orange County Line and Seal Beach.  I-405 south meets CA 22 west at Exit 23.  








I-405 south briefly multiplexes CA 22 east through Seal Beach.  CA 22 east splits from I-405 south via Exit 21 in Westminster.







I-405 south continues through Westminster and meets CA 39 on Beach Boulevard at Exit 16. 






I-405 south passes through Fountain Valley and Costa Mesa where it meets CA 73 at Exit 10.






I-405 south meets CA 55 north at Exit 9A. 







Access to John Wayne Airport is signed from I-405 south Exit 8 on MacArthur Boulevard. 


I-405 enters the City of Irvine and meets CA 133.  CA 133 is the defacto access point for I-405 south traffic to reach I-5 north.




I-405 south terminates in Irvine as it merges into I-5 south.  There is no direct access ramp between I-405 south and I-5 north. 





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