The back way to San Jose; CA 130 over Mount Hamilton

[Max Rockatansky]

CA 275 (unsigned) on the tower bridge come to mind as an orphan.

https://www.cahighways.org/273-280.html#275

[sparker]

Has CA-130 ever been signed off I-680?

I'm sure it was once, but I didn't see anything on 680 while searching the current GSV images.

There has never been any CA 130 signage from I-680 save the original small stenciling on the Alum Rock Ave. overpass indicating the separation between state highways.  Next time I'm over that way during the day I'll try to see if even that's been changed due to the relinquishment of Alum Rock.   Knowing D4, it's still there; they take their sweet time about most things around these parts.   

It's certainly weird that CA 130 used to be signed at US 101 but never signed at I-680, given that I-680 is along the middle of the route (and closer to the section connecting to Mt Hamilton).

So now as Max has said that CA 130 is orphaned, and does not connect to any other state highway (including US and State routes).  Are there any other orphaned highways in CA that are not part of the network?

Much of the signage within the city of San Jose on both I-280 and I-680 dates back at least 25-30 years -- but, still, the omission of any CA 130 reference on 680 is indeed perplexing.  But there was never any indication regarding CA 130 even from US 101 until the Alum Rock/Santa Clara Ave. interchange was rebuilt in the mid-90's (prior to that it was a 4-lane bottleneck in the route, having been constructed as part of the old Bayshore Highway in the late '30's).  CA 130 signage from US 101 showed up about that time on both the exit BGS's and the secondary signage on the C/D system shared with the adjacent McKee Road interchange -- but once the ramps intersected Alum Rock Avenue itself, the "trailblazing" system stopped abruptly; there was no indication that CA 130 only extended east from the interchange, not west along Santa Clara Avenue; that portion was relinquished to the city of San Jose back about 1963 after the then-CA 17 (now the southern end of I-880) freeway was completed.  Full signage of CA 130 and its approaches never seems to have been a priority of Caltrans' District 4 from the establishment of that designation in 1964. 

[DTComposer]

Has CA-130 ever been signed off I-680?

I'm sure it was once, but I didn't see anything on 680 while searching the current GSV images.

There has never been any CA 130 signage from I-680 save the original small stenciling on the Alum Rock Ave. overpass indicating the separation between state highways.  Next time I'm over that way during the day I'll try to see if even that's been changed due to the relinquishment of Alum Rock.   Knowing D4, it's still there; they take their sweet time about most things around these parts.   

It's certainly weird that CA 130 used to be signed at US 101 but never signed at I-680, given that I-680 is along the middle of the route (and closer to the section connecting to Mt Hamilton).

So now as Max has said that CA 130 is orphaned, and does not connect to any other state highway (including US and State routes).  Are there any other orphaned highways in CA that are not part of the network?

Much of the signage within the city of San Jose on both I-280 and I-680 dates back at least 25-30 years -- but, still, the omission of any CA 130 reference on 680 is indeed perplexing.  But there was never any indication regarding CA 130 even from US 101 until the Alum Rock/Santa Clara Ave. interchange was rebuilt in the mid-90's (prior to that it was a 4-lane bottleneck in the route, having been constructed as part of the old Bayshore Highway in the late '30's).  CA 130 signage from US 101 showed up about that time on both the exit BGS's and the secondary signage on the C/D system shared with the adjacent McKee Road interchange -- but once the ramps intersected Alum Rock Avenue itself, the "trailblazing" system stopped abruptly; there was no indication that CA 130 only extended east from the interchange, not west along Santa Clara Avenue; that portion was relinquished to the city of San Jose back about 1963 after the then-CA 17 (now the southern end of I-880) freeway was completed.  Full signage of CA 130 and its approaches never seems to have been a priority of Caltrans' District 4 from the establishment of that designation in 1964. 

Looking at the Caltrans maps this is more interesting than I originally thought:

LRN 115 was originally defined as LRN 5 (signed CA-17) to Mt. Hamilton. This was Santa Clara Street, starting at 13th Street and heading northeast on Santa Clara and Alum Rock Avenue.

In 1959, the portion from LRN 5 to LRN 68 (i.e., Santa Clara Street between 13th Street (CA-17) and the Bayshore Freeway (US-101)) was shifted to an unconstructed routing between LRN 239 and LRN 68 (today's I-280 between CA-17/I-880 and US-101).
The second section (Alum Rock Avenue from US-101 and going to Mt. Hamilton) was then extended over to Patterson.

Then in 1961, the first section was given to LRN 5 (I would guess in anticipation of the CA-17/I-280 switch that ended up not happening), leaving LRN 115 as the route that became CA-130 in 1964.

[sparker]

Curiously, the portion of old SSR 17 using Oakland Road and Main Street in Milpitas between the Bayshore Freeway and the present CA 262 Warm Springs connector between present I-880 and I-680 was kept in the state-maintained system well after the SSR (later CA) 17 freeway was finished circa 1961.  It was part of LRN 5; the freeway itself became an extension of LRN 69 first down to the Bayshore Freeway and later down to the present I-280/880/CA 17 interchange.  After 1964 the LRN 5 surface facility through Milpitas was redesignated -- and actually signed in the field -- as CA 238.  It didn't get relinquished until after I-680 was extended down to the Bayshore/US 101 interchange in the mid-70's, when CA 238 was truncated back to its present southern end at I-680 near Mission de San Jose.  Apparently Caltrans intended the southern extension of CA 238 to be used until I-680 was extended south.  I remember using I-680 back in 1969 when the southern end was at Sunol; the portion over the hill into Fremont wasn't completed until early 1970; at that time, traffic was shunted into Niles Canyon because the new freeway sat atop the old CA 21 alignment over the Sunol Grade, so the old alignment was severed for a couple of years.  It was opened down as far as Calaveras Blvd. by mid-1971 (I was using it about a week after it opened on a later Bay Area trip); the Calaveras Blvd./CA 237 extension opened about the same time.  But I remembered seeing trailblazer signage for CA 238 on Calaveras at the foot of the RR overcrossing in central Milpitas; it was still on Main Street (under the bridge) at the time.  The truncation of 238 happened about 1974 or so coincident with the deployment of a new Western Pacific (now UP) classification yard in Milpitas to serve the Ford assembly plant there (now long gone and replaced by a regional mall); Main Street crossed the tracks at grade there, so it had to be severed to deploy the yard.  There is no direct current alignment; to even approximate the former route requires a detour either several blocks west or east.  The WP rail corridor, truncated to Milpitas in the late '80's when the Ford plant shut down but cut all the way back to Niles Canyon by 2014, is now the location of the under-development BART San Jose extension.       

[TheStranger]

I've seen the 238 section in Milpitas noted on maps of the era so nice to see some confirmation of that being in the field!  Quick question: Does that mean that Route 262's history went something like this:

1930s-1964: Route 9 and 21
1964-1974: Route 238?  (could this be like, say, the situation in Concord where today's Route 242 was legislatively defined in 1964, but signed under its 1930s-1963 designation of Route 24 until 1990)
1975-2002: completely unsigned as Route 262
2002: signed off of I-680 for the first time but no trailblazers on Mission Boulevard itself

Likewise, does this also mean that the Mission San Jose portion of Mission Boulevard/former Route 9 and 21 was Route 238 from about 1964-1970 before 680 was built there?

[sparker]

I've seen the 238 section in Milpitas noted on maps of the era so nice to see some confirmation of that being in the field!  Quick question: Does that mean that Route 262's history went something like this:

1930s-1964: Route 9 and 21
1964-1974: Route 238?  (could this be like, say, the situation in Concord where today's Route 242 was legislatively defined in 1964, but signed under its 1930s-1963 designation of Route 24 until 1990)
1975-2002: completely unsigned as Route 262
2002: signed off of I-680 for the first time but no trailblazers on Mission Boulevard itself

Likewise, does this also mean that the Mission San Jose portion of Mission Boulevard/former Route 9 and 21 was Route 238 from about 1964-1970 before 680 was built there?

That's pretty much it.  262 as an unsigned highway was applied to the short segment of the present connector between Warm Springs Blvd. (which was 238 south of there from 1964 to about 1975 or so) and (then) CA 17, now I-880.  When 238 was truncated, the portion east of I-680 and between the two interchanges was relinquished (the city of Fremont wanted to change it into a suburban arterial) and the I-880>I-680 connector fully was designated CA 262; as stated above, only trailblazer BGS signage from SB I-680 recognizes CA 262; there are zero standalone shields on the connector, referred to via signage as Mission Blvd.

[Techknow]

Surprisingly enough, CA 130 is closed from Quimby Road to Mt. Hamilton due to snow. A friend of mine wanted to visit the observatory to see the snow, and he was prepared to deal with all sorts of drivers that had the same idea too

[Max Rockatansky]

Surprisingly enough, CA 130 is closed from Quimby Road to Mt. Hamilton due to snow. A friend of mine wanted to visit the observatory to see the snow, and he was prepared to deal with all sorts of drivers that had the same idea too

I was under the impression it usually closes down once or twice almost every winter.  Really there isn't much point in putting chain controls in place other than for people that are stationed up at Lick.

[DTComposer]

I've seen the 238 section in Milpitas noted on maps of the era so nice to see some confirmation of that being in the field!  Quick question: Does that mean that Route 262's history went something like this:

1930s-1964: Route 9 and 21
1964-1974: Route 238?  (could this be like, say, the situation in Concord where today's Route 242 was legislatively defined in 1964, but signed under its 1930s-1963 designation of Route 24 until 1990)
1975-2002: completely unsigned as Route 262
2002: signed off of I-680 for the first time but no trailblazers on Mission Boulevard itself

Likewise, does this also mean that the Mission San Jose portion of Mission Boulevard/former Route 9 and 21 was Route 238 from about 1964-1970 before 680 was built there?

That's pretty much it.  262 as an unsigned highway was applied to the short segment of the present connector between Warm Springs Blvd. (which was 238 south of there from 1964 to about 1975 or so) and (then) CA 17, now I-880.  When 238 was truncated, the portion east of I-680 and between the two interchanges was relinquished (the city of Fremont wanted to change it into a suburban arterial) and the I-880>I-680 connector fully was designated CA 262; as stated above, only trailblazer BGS signage from SB I-680 recognizes CA 262; there are zero standalone shields on the connector, referred to via signage as Mission Blvd.

The relatively new street signs on the signals at Mission Blvd and Warm Springs Blvd now say "Mission Blvd/CA-262."  I'll try to get a pic next time I'm there this week.

[TheStranger]

One other note about Route 262 I forgot to mention:

Pre-1965 or so, I-680 was slated to enter San Jose via today's I-880 (then Route 17) south of 262 all the way to 101, while 280 "south" went north on Route 17 between the area near today's Santana Row shopping center and US 101.  So I have always been under the impression that 262 was the original planned corridor for 680 between Warm Springs and 880, with today's 680 south of Warm Springs coming about as the result of some complicated route definition changes.  (IIRC there was a thread several years ago on this, in which I recall discovering that the 1964-1965 legislative definition of Route 17 included what is now modern 280 and 680 between 880 and 262)

Essentially, the short freeway portion of 262 west of Warm Springs Boulevard was built to be (but likely never signed as) a segment of 680, only to be downgraded to a short state route when the Milpitas bypass became part of the interstate!  And then (as sparker noted) 262 expanded to take over a portion of 238 once 238 was truncated between Fremont and San Jose. 

It's fascinating to see this route's evolution over the years on the online roadgeek forums, and in general: starting out as an unsigned remnant of an old Interstate planned routing, then expanding to be a slightly longer connector taking over former Route 9/21 (238), then getting signage at one terminus along 680 with supplemental signage along the Fastrak/carpool lane...and finally being acknowledged on Mission Boulevard itself according to DTComposer's new info!  Funny enough, the 2002-2017 level of signage for 262v(at one terminus only) is already almost as good as other short state highway connectors like Route 221 in Napa.

Not bad for a route that was supposed to be decommissioned once a 237 freeway was constructed diagonally from 880 to 680, only for that to be shelved permanently.

[sparker]

One other note about Route 262 I forgot to mention:

Pre-1965 or so, I-680 was slated to enter San Jose via today's I-880 (then Route 17) south of 262 all the way to 101, while 280 "south" went north on Route 17 between the area near today's Santana Row shopping center and US 101.  So I have always been under the impression that 262 was the original planned corridor for 680 between Warm Springs and 880, with today's 680 south of Warm Springs coming about as the result of some complicated route definition changes.  (IIRC there was a thread several years ago on this, in which I recall discovering that the 1964-1965 legislative definition of Route 17 included what is now modern 280 and 680 between 880 and 262)

Essentially, the short freeway portion of 262 west of Warm Springs Boulevard was built to be (but likely never signed as) a segment of 680, only to be downgraded to a short state route when the Milpitas bypass became part of the interstate!  And then (as sparker noted) 262 expanded to take over a portion of 238 once 238 was truncated between Fremont and San Jose. 

It's fascinating to see this route's evolution over the years on the online roadgeek forums, and in general: starting out as an unsigned remnant of an old Interstate planned routing, then expanding to be a slightly longer connector taking over former Route 9/21 (238), then getting signage at one terminus along 680 with supplemental signage along the Fastrak/carpool lane...and finally being acknowledged on Mission Boulevard itself according to DTComposer's new info!  Funny enough, the 2002-2017 level of signage for 262v(at one terminus only) is already almost as good as other short state highway connectors like Route 221 in Napa.

Not bad for a route that was supposed to be decommissioned once a 237 freeway was constructed diagonally from 880 to 680, only for that to be shelved permanently.

That's correct; originally the portion of I-280 between CA 17 and US 101 and I-680 from US 101 to present CA 262 was "inked in" as CA 17; the switch occurred circa 1965 when (a) a few additional Interstate miles became available after the truncation of I-480 and I-80 in SF, not to mention the shift of I-280 from the originally planned 19th Avenue alignment over to the Southern (nee' CA 82) Freeway routing where it sits today, and (b) the realization that much of the previous I-680 mileage over (later) CA 17 was substandard, having been "grandfathered" into the system in '56.  The Division of Highways decided that rerouting the Interstate over the former CA 17 corridor (which had been formally adopted some years earlier, with property acquisition already underway) would save money in the long run, since Interstate standards could be applied to that corridor, which was going to be constructed in any case, and some costly aspects endemic to the original Interstate corridor (such as the eventual reconstruction of CA 17 to full Interstate standards and the construction of the connecting corridor across Warm Springs) could be avoided.  Interestingly, as a money-saving measure, the I-280/680/US 101 interchange east of downtown San Jose wasn't fully deployed at first, with a lot of indirect movement via Story Road and McLaughlin Ave; this was a point of contention between San Jose city officials and Caltrans in the mid-70's, culminating in the completion of the interchange circa 1982.

I'm going up I-880 to Alameda on business tomorrow; I'll try to sneak over to Warm Springs Blvd. to see the new CA 262 references (probably on street signs hung under signal arms; that intersection has been undergoing revamping for several months now).

[TheStranger]

That's correct; originally the portion of I-280 between CA 17 and US 101 and I-680 from US 101 to present CA 262 was "inked in" as CA 17; the switch occurred circa 1965 when (a) a few additional Interstate miles became available after the truncation of I-480 and I-80 in SF, not to mention the shift of I-280 from the originally planned 19th Avenue alignment over to the Southern (nee' CA 82) Freeway routing where it sits today, and (b) the realization that much of the previous I-680 mileage over (later) CA 17 was substandard, having been "grandfathered" into the system in '56.  The Division of Highways decided that rerouting the Interstate over the former CA 17 corridor (which had been formally adopted some years earlier, with property acquisition already underway) would save money in the long run, since Interstate standards could be applied to that corridor, which was going to be constructed in any case, and some costly aspects endemic to the original Interstate corridor (such as the eventual reconstruction of CA 17 to full Interstate standards and the construction of the connecting corridor across Warm Springs) could be avoided.

In hindsight, it's amusing how 17 south of there did become an Interstate anyway in 1984 - though the 101/880 cloverleaf remains (I suspect that is due to the proximity of San Jose's airport, which would make flyover heights hard to manage were that interchange reconstructed).

Also sounds like the original plan was for today's 262 route in Fremont to essentially be a wrong-way multiplex from 1956-1965 (680 south along there would be concurrent with 17 north, and vice versa) until the route swap. 

How much of 17 (880) between 101 and today's 262 was ever signed as 680? 

Looking at Historicaerials.com, the short freeway stub west of Warm Springs to today's 880 already existed in 1959!  The Warm Springs/Mission intersection was pretty undeveloped at the time - so it's easy to see how this was a viable Interstate corridor back then.  By the 1966 aerial photo though, housing developments started to spring up nearby, maybe as a consequence of that route no longer being part of the 680 proposal.  (In 1948, the Warm Springs/Mission intersection was an at-grade Y junction, with Mission (Route 21 and the continuation of Route 9) actually beginning at Warm Springs/what was then Route 17 & Route 9)  The 1969 topographic map on that page does show the start of the shopping center on the southeast corner where Safeway is now.

[sparker]

The last segment of the historically SSR 17 freeway through San Jose, between Stevens Creek Blvd. and Bayshore Blvd., just north of the present 101/880 interchange, was completed in 1961; this included the (then) Bypass 101 interchange.  I-680 was indeed signed (something I remember from my 1963 trip with my parents) north of Bypass 101, while I-280 was signed along with SSR 17 along the freeway from Stevens Creek to Bypass 101; the begin 680/end 280 (and vice-versa) point was originally at the Bypass 101 interchange.  A leg of a later college-tour trip (early '65) took me from the just-opened UC Santa Cruz north via CA 17 to our next stop at Berkeley; of course the bus used CA 17 for most of the trip -- and it was still signed as I-280 from the construction area south of Stevens Creek Blvd. where I-280 would diverge for its trip up the Peninsula (construction was well under way then) and I-680 north of US 101 -- but only as far as the Warm Springs exit -- which was still marked as CA 21.  I didn't venture into the area again until about '68, when the revised-alignment I-680 was being built; by that time the exit had been re-signed as "Temporary I-680", the I-680 and I-280 reassurance shields were gone but there was signage indicating that CA 17 was "Temporary I-280 and Temporary I-680", possibly to funnel traffic from US 101 to the stub ends of those two nascent facilities (the first segment of I-280 west of CA 17 opened in early 1966).  While it took another 4 years after that for I-680 to extend south from Pleasanton down into Fremont, the original state highways (21 and later 84) did serve as "trailblazed" connectors to the south end of completed I-680 (which inched southward year by year).  What is now 262 has undergone many iterations and designation changes from its inception circa 1954-55 (when the first section of the SSR 17 freeway, from Bayshore Blvd. north to and including the west portion of the Warm Springs "cutoff", was completed: SSR 9/17, SSR 9/21, unsigned but later Temporary I-680 (with CA 238 sharing the portion east of Warm Springs Blvd.), nothing but "TO CA 17"/later "TO I-880" signs along I-680 or CA 17/I-880, and now sporadically and back-handedly CA 262 (with the "TO" signage remaining intact along the two Interstates).   

[Kniwt]

A possible/likely reason why CA-262 magically started appearing was the addition of HOT lane on southbound I-680 a few years back. The variable toll signs needed to distinguish between the Mission Blvd. north exit (CA-238), where there's no exit from the HOT lane, and the Mission Blvd. south exit (CA-262). Since "Mission Blvd. north" and "Mission Blvd. south" could be misinterpreted, the route numbers probably were the next best thing.

[sparker]

A possible/likely reason why CA-262 magically started appearing was the addition of HOT lane on southbound I-680 a few years back. The variable toll signs needed to distinguish between the Mission Blvd. north exit (CA-238), where there's no exit from the HOT lane, and the Mission Blvd. south exit (CA-262). Since "Mission Blvd. north" and "Mission Blvd. south" could be misinterpreted, the route numbers probably were the next best thing.

Possibly, but not probably; CT District 4 just ain't that smart!  The CA 262 trailblazer signage from SB I-680 is probably just signing specs that were interpreted to show CA 262 as a signed facility (that very thing has happened in the past, not only in this district but others as well) when there was no actual mandate to sign it (probably similar to CA 221 up in Napa County).  Actually, the CA 262 trailblazers are exemplary by D4 standards; attractive or even competent signage doesn't seem to be their forte'!   

[mrsman]

A possible/likely reason why CA-262 magically started appearing was the addition of HOT lane on southbound I-680 a few years back. The variable toll signs needed to distinguish between the Mission Blvd. north exit (CA-238), where there's no exit from the HOT lane, and the Mission Blvd. south exit (CA-262). Since "Mission Blvd. north" and "Mission Blvd. south" could be misinterpreted, the route numbers probably were the next best thing.

Possibly, but not probably; CT District 4 just ain't that smart!  The CA 262 trailblazer signage from SB I-680 is probably just signing specs that were interpreted to show CA 262 as a signed facility (that very thing has happened in the past, not only in this district but others as well) when there was no actual mandate to sign it (probably similar to CA 221 up in Napa County).  Actually, the CA 262 trailblazers are exemplary by D4 standards; attractive or even competent signage doesn't seem to be their forte'!   

This conversation has had me take a closer look at Napa.  It's amazing to me, given California's penchant for avoiding multiplexes, that there are several multiplexes of 29/121 29/12 and 12/121.  It's also surprising given how long a multiplex for 12/121.

[sparker]

A possible/likely reason why CA-262 magically started appearing was the addition of HOT lane on southbound I-680 a few years back. The variable toll signs needed to distinguish between the Mission Blvd. north exit (CA-238), where there's no exit from the HOT lane, and the Mission Blvd. south exit (CA-262). Since "Mission Blvd. north" and "Mission Blvd. south" could be misinterpreted, the route numbers probably were the next best thing.

Possibly, but not probably; CT District 4 just ain't that smart!  The CA 262 trailblazer signage from SB I-680 is probably just signing specs that were interpreted to show CA 262 as a signed facility (that very thing has happened in the past, not only in this district but others as well) when there was no actual mandate to sign it (probably similar to CA 221 up in Napa County).  Actually, the CA 262 trailblazers are exemplary by D4 standards; attractive or even competent signage doesn't seem to be their forte'!   

This conversation has had me take a closer look at Napa.  It's amazing to me, given California's penchant for avoiding multiplexes, that there are several multiplexes of 29/121 29/12 and 12/121.  It's also surprising given how long a multiplex for 12/121.

About the only consistent current reasons for multiplexes in CA are (a) continuity, (b) economy' and (3) topography.   Topography was a very prominent reason pre-'64 (such as with the multiple designations over both Cajon and Beaumont summits in SoCal), but enough routes were truncated or deleted to avoid that particular scenario in most cases.  The multiplexed state routes around Napa are some of the remaining topographically-influenced multiplexes; avoiding both the mountain ridges on both sides of the valley as well as the Napa River and the wetlands between Napa and Vallejo.  You' will find some short multiplexes on certain freeways (US 101 seems to feature more of them than any other route (I can think of 13 right off the cuff), but much of that is because some cities elected to go the relinquishment route for the former city routes of the intersecting highways rather than have through traffic in the city centers.  And that satisfies the economy factor; Caltrans only has to maintain the freeway and what's left of the intersecting routes away from the central cities.  Some of the multiplexes, particularly along US 101, are somewhat lengthy (CA 116 and CA 128 in the North Bay area being two of the longest); that is to maintain continuity between the segments of the intersecting route -- but topography comes into play as well; with 101 serving as a "conduit" between favorable valleys/passes/saddles/etc. where the intersecting route diverges toward another region.           

[Max Rockatansky]

A possible/likely reason why CA-262 magically started appearing was the addition of HOT lane on southbound I-680 a few years back. The variable toll signs needed to distinguish between the Mission Blvd. north exit (CA-238), where there's no exit from the HOT lane, and the Mission Blvd. south exit (CA-262). Since "Mission Blvd. north" and "Mission Blvd. south" could be misinterpreted, the route numbers probably were the next best thing.

Possibly, but not probably; CT District 4 just ain't that smart!  The CA 262 trailblazer signage from SB I-680 is probably just signing specs that were interpreted to show CA 262 as a signed facility (that very thing has happened in the past, not only in this district but others as well) when there was no actual mandate to sign it (probably similar to CA 221 up in Napa County).  Actually, the CA 262 trailblazers are exemplary by D4 standards; attractive or even competent signage doesn't seem to be their forte'!   

This conversation has had me take a closer look at Napa.  It's amazing to me, given California's penchant for avoiding multiplexes, that there are several multiplexes of 29/121 29/12 and 12/121.  It's also surprising given how long a multiplex for 12/121.

About the only consistent current reasons for multiplexes in CA are (a) continuity, (b) economy' and (3) topography.   Topography was a very prominent reason pre-'64 (such as with the multiple designations over both Cajon and Beaumont summits in SoCal), but enough routes were truncated or deleted to avoid that particular scenario in most cases.  The multiplexed state routes around Napa are some of the remaining topographically-influenced multiplexes; avoiding both the mountain ridges on both sides of the valley as well as the Napa River and the wetlands between Napa and Vallejo.  You' will find some short multiplexes on certain freeways (US 101 seems to feature more of them than any other route (I can think of 13 right off the cuff), but much of that is because some cities elected to go the relinquishment route for the former city routes of the intersecting highways rather than have through traffic in the city centers.  And that satisfies the economy factor; Caltrans only has to maintain the freeway and what's left of the intersecting routes away from the central cities.  Some of the multiplexes, particularly along US 101, are somewhat lengthy (CA 116 and CA 128 in the North Bay area being two of the longest); that is to maintain continuity between the segments of the intersecting route -- but topography comes into play as well; with 101 serving as a "conduit" between favorable valleys/passes/saddles/etc. where the intersecting route diverges toward another region.         

There is actually quite a bit of multiplexing involving CA 49, 108, and 120.  Basically those routes are all constrained by the terrain and generally branch off differently enough that it makes the multiplexes make sense.  CA 49 has some even weirder concurrencies to the north with CA 193 being completely silent and 89 being a reverse concurrency.