Interstate 5

[Max Rockatansky]

Since I frequent I-5 so much I figured it was high time to start start a series dedicated to the modern freeway alignment.  The first blog in the series covers I-5 from CA 54 in National City north to CA 99 in San Joaquin Valley via the; Montgomery Freeway, Santa Ana Freeway and Golden State Freeway. 

https://www.gribblenation.org/2019/05/interstate-5-southern-san-diego-county.html

[TheStranger]

A subtle interesting note looking at the 1965 map listed:

This confirms something I had seen on a Rand McNally map from 1967, that the portion of modern Route 125 between I-8 and Route 94 was signed as Route 67 in the 1960s (and for several years after 125 was first defined).  Not sure when the signage switched over to 125, but it seems this freeway connector was built as 67 originally, well before the portions of modern 125 north of I-8 and south of Route 94 were started.

[sparker]

A subtle interesting note looking at the 1965 map listed:

This confirms something I had seen on a Rand McNally map from 1967, that the portion of modern Route 125 between I-8 and Route 94 was signed as Route 67 in the 1960s (and for several years after 125 was first defined).  Not sure when the signage switched over to 125, but it seems this freeway connector was built as 67 originally, well before the portions of modern 125 north of I-8 and south of Route 94 were started.

Absolutely correct; SSR 67 from SSR 94 to US 80 was established in the '50's; it was part of the longish LRN 198, which comprised SSR 94 from US 395 in downtown San Diego to SSR 67, SSR 67 from that point through El Cajon and then north to SSR 78 in Ramona, then the rest of SSR 78 east to then-US 99 (now CA 86) near the south end of the Salton Sea.  It was a series of surface streets in the Lemon Grove area until the freeway was built (essentially a freeway continuation of the '50's-built SSR 94 freeway; 94 exited onto the surface Campo Road while SSR 67 took over the freeway alignment heading northeast).  SSR 67 multiplexed over US 80 into El Cajon, then took off on its own northward.  IIRC, it retained the "67" number in the field well after '64; eventually giving way as the first signed segment of CA 125.   I don't know the exact date of the switchover, but I do remember seeing 67 signage (with black-on-white later-issue shields, no less) on that freeway as late as 1968. 

[dbz77]

Since I frequent I-5 so much I figured it was high time to start start a series dedicated to the modern freeway alignment.  The first blog in the series covers I-5 from CA 54 in National City north to CA 99 in San Joaquin Valley via the; Montgomery Freeway, Santa Ana Freeway and Golden State Freeway. 

https://www.gribblenation.org/2019/05/interstate-5-southern-san-diego-county.html

Interesting.

I am wondering why the first 5/99 interchange, was designed such that I-5 is basically exiting from the mainlines.

[sparker]

Since I frequent I-5 so much I figured it was high time to start start a series dedicated to the modern freeway alignment.  The first blog in the series covers I-5 from CA 54 in National City north to CA 99 in San Joaquin Valley via the; Montgomery Freeway, Santa Ana Freeway and Golden State Freeway. 

https://www.gribblenation.org/2019/05/interstate-5-southern-san-diego-county.html

Interesting.

I am wondering why the first 5/99 interchange, was designed such that I-5 is basically exiting from the mainlines.

That was one of the earlier 6+ lane sections of US 99, dating from about 1962; as the I-5/Westside alignment had been adopted several years earlier and the interchange location had been finalized, it was decided that it was not worth the effort to tear up the existing alignment just to place the I-5 divergence on the left side of the NB carriageway.  In addition, it was calculated that it would be safer to diverge I-5's truck traffic from the right side rather than require them to merge to the left -- particularly as they were (and are) on a relatively steep downgrade at the interchange's location.  So along with the 6-lane upgrading of former US 99, the initial berm to carry the I-5 diverging ramp was simultaneously constructed.   Southbound, that steep gradient eventually caused problems with slow trucks SB from CA 99 interfering with a "clean" merge from I-5; the present separation of truck lanes from auto lanes was subsequently implemented (this also helped with CA 99 trucks accessing the Grapevine scales).  Yeah, technically NB it's a TOTSO -- but a pretty high-speed one in any case;  I-5 in CA does have a few of them!   

[TheStranger]

That was one of the earlier 6+ lane sections of US 99, dating from about 1962; as the I-5/Westside alignment had been adopted several years earlier and the interchange location had been finalized, it was decided that it was not worth the effort to tear up the existing alignment just to place the I-5 divergence on the left side of the NB carriageway.  In addition, it was calculated that it would be safer to diverge I-5's truck traffic from the right side rather than require them to merge to the left -- particularly as they were (and are) on a relatively steep downgrade at the interchange's location.  So along with the 6-lane upgrading of former US 99, the initial berm to carry the I-5 diverging ramp was simultaneously constructed.   Southbound, that steep gradient eventually caused problems with slow trucks SB from CA 99 interfering with a "clean" merge from I-5; the present separation of truck lanes from auto lanes was subsequently implemented (this also helped with CA 99 trucks accessing the Grapevine scales).  Yeah, technically NB it's a TOTSO -- but a pretty high-speed one in any case;  I-5 in CA does have a few of them!   

A couple of interesting thoughts in that regard:

- First off, doesn't I-5 do a TOTSO as early on as in San Diego southbound at the north I-805 junction?  It's amazing how many of them there are overall on the route!

- In that vein, I went through the East Los Angeles interchange recently and there's a part of me that wonders if the whole setup would have been much more easily accomplished if instead of a new Golden State Freeway alignment (which now carries the 5/10 concurrency) between the San Bernardino Freeway and the Santa Ana/Santa Monica Freeways, I-5/US 99 continued directly south into the San Bernardino Split and that whole junction was rebuilt as a stack of some sort.  Seems almost like the Golden State Freeway's short east bypass through Boyle Heights was done for much the same reason that the West Side Freeway exits off of the 99/5 junction of THAT portion of the Golden State, a simple attempt at not disrupting an existing through route.  In retrospect, the 99/5 split in Wheeler Ridge works better due to traffic volumes being pretty equal for both directions of the northbound split, while I-5 exiting US 101/Santa Ana Freeway in East Los Angeles is a little less perfect due to only two through lanes continuing onto the Santa Ana slot segment and the majority of northbound lanes instead doing the "exit" to the Golden State!

- The TOTSO for 580/5 makes sense in the context of 580 being planned originally as 5W (and thus seen as a continuation of 5, rather than an auxiliary route), and the purposefulness of the West Side Freeway's existence as a primary alternate Bay Area-LA route compared to the older, longer 101.  Side effect of Interstate-funded new-terrain bypasses in California though: the old US route alignment ends up taking much longer to have their stoplights removed fully: US 101 in 1992 (specifically in Santa Barbara) between SF and LA, I-215 (old US 395) in 1994 south of Moreno Valley, and Route 99 in 1997 in Atwater.

- After the 580/5 split, the next TOTSO for I-5 is in Portland at I-405 (in part, like Wheeler Ridge, induced due to the existence of a (former) US 99 through alignment at the time 5 was built there)

- I-5's TOTSO at the East Los Angeles Interchange also created a TOTSO for I-10, which exits onto 5 to then continue into the Santa Monica Freeway eventually.  US 99 also briefly had a TOTSO there in the early 1960s, with only 70 continuing to the San Bernardino Split and US 101.  Interestingly while the San Bernardino Freeway is a pretty old corridor, the same effect I-5 had on US 101/Route 99 above (and I-15 had on I-215) is happening too, with the old Route 60 corridor still not fully upgraded to freeway west of Beaumont!  What's different in the 10/60 example due to the 5/101/99 and 15/215 examples: 10 itself was never new terrain (as it used old 70/99 entirely) until the Santa Monica Freeway, while 60 between the East Los Angeles Interchange and Route 71 was built from the ground up in the 1960s.  Even though 60 is the shorter route between Beaumont and the East Los Angeles Interchange, 10 got signed pretty quickly on an already existing freeway with the jog along I-5 de facto deemed worth it to have a no-stoplight corridor in place ASAP.

[sparker]

^^^^^^^^^^
Regarding the concept of simply continuing the Golden State Freeway south directly onto the Santa Ana at the "San Bernardino Split":  three things worked against that idea -- first, the area's topology.  The "split", and that particular section of the Santa Ana Freeway, are at the bottom of a bluff and occupying part of the L.A. river floodplain (which is technically less so since the river was concrete-lined back in the '20's and '30's), so to enlarge the old and compact interchange to accommodate a new 8-lane freeway coming in from the north would have been problematic without carving out large chunks of the bluff.  The second problem was the Southern Pacific intermodal freight yard, built right after WWII and sited between the L.A. River and the Daly St. (LRN 4) bridge.  It was a bit over a half-mile across north-to-south, and any freeway bridge would have had to not only cross all the tracks but the truck parking area adjacent to the yard (back in those days, "intermodal" involved TOFC -- trailers on flat cars, or, in the more common parlance, "piggyback"; containers weren't common until the late '60's), which was to hold about 200 trucks at any given time.  The yard's southern edge ran along Mission St., which was only about a quarter-mile north of the San Bernardino Split; it's more than likely that the number of ramps needed for all movements would have had to themselves impinge on the yard -- it would have had to be some sort of "stack" interchange, with the Golden State/Santa Ana as one axis and the San Bernardino/Hollywood (a little poetic license here regarding names -- meaning the part of US 101 through the Civic Center "trough") as the E-W axis.   Given the proximity of the L.A. River and the various properties around there that would have had to be razed or extensively modified, the idea of a major interchange at that location would have been next to impossible.  The third consideration is the Santa Monica/Pomona Freeway continuum -- the portion of the Santa Ana Freeway below the Boyle Heights bluffs would have had to be 10-12 lanes to accommodate I-5, I-10, and US 101 (pre-truncation) traffic between the E-W freeways.  Again, that would have involved "bluff-carving" or, alternately, the taking of the sizeable warehouse properties between the freeway and the river. 

But the actual deciding factor to place the Golden State where it finally ended up was the Division of Highway's desire to keep the through Interstates away from the existing freeways radiating from downtown L.A. at the 4-level interchange and create a "loop" around downtown for commercial traffic dispersal.   The I-5/I-10 arc through the ELA interchange was the heart of that loop.   Besides, the initial ELA plans called for a southern extension of the Golden State (tentatively labeled the "Industrial" freeway) south paralleling Alameda Ave. all the way to the Port of Los Angeles; this was later modified into the initial CA 47 freeway corridor that never actually gained full traction except in later years as a dedicated port server system. 

[mrsman]

^^^^^^^^^^
Regarding the concept of simply continuing the Golden State Freeway south directly onto the Santa Ana at the "San Bernardino Split":  three things worked against that idea -- first, the area's topology.  The "split", and that particular section of the Santa Ana Freeway, are at the bottom of a bluff and occupying part of the L.A. river floodplain (which is technically less so since the river was concrete-lined back in the '20's and '30's), so to enlarge the old and compact interchange to accommodate a new 8-lane freeway coming in from the north would have been problematic without carving out large chunks of the bluff.  The second problem was the Southern Pacific intermodal freight yard, built right after WWII and sited between the L.A. River and the Daly St. (LRN 4) bridge.  It was a bit over a half-mile across north-to-south, and any freeway bridge would have had to not only cross all the tracks but the truck parking area adjacent to the yard (back in those days, "intermodal" involved TOFC -- trailers on flat cars, or, in the more common parlance, "piggyback"; containers weren't common until the late '60's), which was to hold about 200 trucks at any given time.  The yard's southern edge ran along Mission St., which was only about a quarter-mile north of the San Bernardino Split; it's more than likely that the number of ramps needed for all movements would have had to themselves impinge on the yard -- it would have had to be some sort of "stack" interchange, with the Golden State/Santa Ana as one axis and the San Bernardino/Hollywood (a little poetic license here regarding names -- meaning the part of US 101 through the Civic Center "trough") as the E-W axis.   Given the proximity of the L.A. River and the various properties around there that would have had to be razed or extensively modified, the idea of a major interchange at that location would have been next to impossible.  The third consideration is the Santa Monica/Pomona Freeway continuum -- the portion of the Santa Ana Freeway below the Boyle Heights bluffs would have had to be 10-12 lanes to accommodate I-5, I-10, and US 101 (pre-truncation) traffic between the E-W freeways.  Again, that would have involved "bluff-carving" or, alternately, the taking of the sizeable warehouse properties between the freeway and the river. 

But the actual deciding factor to place the Golden State where it finally ended up was the Division of Highway's desire to keep the through Interstates away from the existing freeways radiating from downtown L.A. at the 4-level interchange and create a "loop" around downtown for commercial traffic dispersal.   The I-5/I-10 arc through the ELA interchange was the heart of that loop.   Besides, the initial ELA plans called for a southern extension of the Golden State (tentatively labeled the "Industrial" freeway) south paralleling Alameda Ave. all the way to the Port of Los Angeles; this was later modified into the initial CA 47 freeway corridor that never actually gained full traction except in later years as a dedicated port server system.

Thanks for all the history.

It is interesting to think of the East LA freeways as being in the shape of a capital I (or rotated H) with the Hollywood-San Bernadino along the north, Santa Monica-Pomona on the south, and Golden State-Santa Ana along the N-S axis.  Such though cannot happen.  The Golden State could not be routed into the N-S axis of the 101 Santa Ana for the reasons described by sparker.  And it seems that it would be just as difficult to now get rid of the 101 Santa Ana (between SB SPlit and E LA) in place of ramps connecting the I-5 freeway to the San Bernardino Fwy west (towards 101) in the vicinity of USC hospital.

With all the talk of modern urbanists wanting to get rid of I-345 in Dallas (which I have no understanding as to how that is even possible given the traffic volumes there), it is nice to know that they will not be able to remove the 101-Santa Ana connection because it would be difficult to connect  the Santa Ana Fwy to the Downtown slot without the current 101.

[sparker]

^^^^^^^^^^^
Another interesting tidbit about the freeway configuration in East Los Angeles was that until the widening of the San Bernardino Freeway/I-10 east of the I-5 (Golden State) interchange, the signage on WB I-10 originally only referenced West I-10 on the ramp to the SB Golden State Freeway -- no mention of SB I-5; traffic to SB I-5 (essentially a "backwards" movement regarding the trajectory of the Santa Ana Freeway) was expected to remain on the western "stub" of the San Bernardino Freeway (original I-110 and briefly BGS-signed as such from WB I-10) to the "San Bernardino Split", where it would take the single-lane flyover to the SB Santa Ana Freeway (originally I-105 but never signed -- although prominently featured on Gousha L.A. maps in the early '60's), aka US 101 at that point.  That ramp, signed for SB I-5 after signage was applied to that freeway in 1961-62 and featuring substandard clearance beneath it, was dismantled at the same time of the San Bernardino Freeway upgrades; at which point the ramp carrying WB I-10 was signed as access to both I-10 and SB I-5 as it is today. 

[D-Dey65]

A rare instance for me, but I have an I-5 question; I've been doing some GSV research for I-5 Business routes. Over at Exit 729 (BL-5) in Dunsmuir, there are some unkempt left-turn lanes at the northbound off-ramp and on-ramp at Dunsmuir Avenue (BL-5; Dunsmur/Historic US 99).

https://www.google.com/maps/@41.193195,-122.2841783,3a,75y,13.42h,95.86t/data=!3m7!1e1!3m5!1sthsZUen2J6kcuh1KEG-JuQ!2e0!6s%2F%2Fgeo0.ggpht.com%2Fcbk%3Fpanoid%3DthsZUen2J6kcuh1KEG-JuQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D65.19609%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656?hl=en

Was there some big plan to have real turning ramps there?

[mrsman]

A rare instance for me, but I have an I-5 question; I've been doing some GSV research for I-5 Business routes. Over at Exit 729 (BL-5) in Dunsmuir, there are some unkempt left-turn lanes at the northbound off-ramp and on-ramp at Dunsmuir Avenue (BL-5; Dunsmur/Historic US 99).

https://www.google.com/maps/@41.193195,-122.2841783,3a,75y,13.42h,95.86t/data=!3m7!1e1!3m5!1sthsZUen2J6kcuh1KEG-JuQ!2e0!6s%2F%2Fgeo0.ggpht.com%2Fcbk%3Fpanoid%3DthsZUen2J6kcuh1KEG-JuQ%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D65.19609%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656?hl=en

Was there some big plan to have real turning ramps there?

No historical knowledge of this specifically, but it seems that this was done with the prospect of having Dunsmuir Ave extend south of I-5.  If that were the case, then the exit should resemble a diamond ramp as much as possible, and allow for left turns.  Since there is no Dunsmuir beyond I-5, the only purpose of making a diamond ramp would be to allow people to u-turn onto the highway, so it was not done.