Background on this weird interchange in Santa Barbara?

[Voyager]

Never seen anything like it before, why do the exits on 101 exit center and not on the right but the onramps do? Any background on this?

[Max Rockatansky]

Which exit?

[jrouse]

I'm not entirely sure but I believe it's because the railroad tracks run immediately parallel to US-101 on the south side of the freeway and cross the street at grade.  You can see there would not be sufficient storage space between the ramp intersection and the grade crossing.

US-101 is undergoing substantial reconstruction and widening between Santa Barbara and Carpinteria.  I'm not sure if this interchange will be reconstructed as part of that.  More info can be found at sbroads.com

[Voyager]

Which exit?

Cabrillo and 101 just east of downtown.

[SeriesE]

That particular interchange appears to be completely redundant. Same movements can be made via the ramp to Los Patos Way (SB) and Coast Village Rd (NB)

[DTComposer]

That particular interchange appears to be completely redundant. Same movements can be made via the ramp to Los Patos Way (SB) and Coast Village Rd (NB)

The original alignment of US-101 followed Coast Village Road, Cabrillo Blvd (where it crossed under the RR tracks) and Los Patos Way (crossing under the RR tracks again), connecting to Old Coast Highway and into downtown:

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[url="https://flic.kr/p/2m2eZbY"]BE5E28A3-4542-4FF4-92E6-D47CD2FE41DA by Daniel Thomas, on Flickr

Nowadays, Los Patos is an underpowered off-ramp and isn't even signed as an exit on US-101.

I think (as mentioned above) the interchange design was due to the RR tracks, but I'll dive into CHPW and find some more info.

[pderocco]

The SB side of US-101 could have been moved right next to the NB side, leaving room between it and the tracks for normal ramps, including a SB on-ramp. I assume the logistics of the change would have been difficult since the original road was probably right next to the tracks.

[roadfro]

Interesting that the SB ramp to the Los Patos Way access for Cabrillo has no BGS for it at all. But I'm also seeing that the bridge under the railroad has a 12'3" clearance and is marked with a truck prohibition, so I'm guessing that's why. Otherwise, the redundancy from the center off ramps could've been eliminated. But I'm also curious why they didn't build the two 101 carriageways next to each other and make room for regular SB ramps like pderocco mentioned.

[mrsman]

The whole stretch of US 101 through Santa Barbara area is very constrained on right of way.  Most of it is only 2 lanes in each direction.  I imagine there was significant push by the local community to keep the freeway as close to the railroad as possible, even though the old routing of 101 was on surface street (as DTComposer notes) that made lots of turns in the city of SB.

Looking at an aerial map from 1947, you can see a 4-lane 101 approaching the area along Coast Village Dr.  It seems that the alignment, by this point in time, made a gradual sweeping left onto Cabrillo, which then ducked under the railroad.  The modern highway alignment was also already in place, without the center exits.  It seems that there was no exit at Cabrillo at all, other than the sweeping alignment. 

It seems that the further extension of the freeway south of this point, away from Coast Village and following the railroad corridor, may have led to the anomaly of the left exit.  Coast Village - Cabrillo sweep was eventually designed to be independent of the traffic of 101, but there was a desire to place an exit on 101 for Cabrillo.  It seemed easier to move NB 101 onto a new alignment, and allow the old alignment of 101 (which is now to the left) to remain in place as the left exit onto Cabrillo.

It should also be noted that there is no entrance onto US 101 south anywhere in this area.  Traffic from Cabrillo has to go through the village of Montecito before reaching the onramp near the traffic circle at Olive Mill.

EDITED TO ADD:  Looking at old aerials, it seems that until fairly recently there was a direct ramp from Cabrillo onto 101 SB that entered 101 on the left side.  It seems to have still been in place as late as 2007.

https://www.google.com/maps/@34.4216642,-119.6519874,3a,75y,131.11h,73.97t/data=!3m8!1e1!3m6!1smJtI6xF2f64SRi2eunmdaQ!2e0!5s20071101T000000!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D16.03129558017025%26panoid%3DmJtI6xF2f64SRi2eunmdaQ%26yaw%3D131.11348428522192!7i3328!8i1664?entry=ttu&g_ep=EgoyMDI1MDExMC4wIKXMDSoASAFQAw%3D%3D

I venture to guess that the addition of freeway exits and entrances at Cabrillo was designed so that traffic could reach Cabrillo (an important arterial for the coastal area of the city) without adding to the traffic through the village of Montecito.   Given how close SB 101 was to the railroad, the only feasible way to add the exit and entrance required left side ramps and moving NB 101 out of the way.  Those ramps were created along the old alignment of 101 NB.

Due to the inherent dangers of left side ramps, and more so for entrances rather than exits, the entrance onto SB 101 was closed some time after 2007 without a replacement.

[DTComposer]

^
I remember the left ramp onto SB US-101 from when I lived there in the '90s. It was always a tricky intersection.

Cabrillo Blvd. was part of CA-225 (former LRN 150) and provides direct access to the beach area so it made sense to connect it directly to US-101.

The project pages indicate that they intend to close the Los Patos exit (and RR undercrossing) and re-construct the Cabrillo interchange to be all right-hand ramps:

https://santabarbaraca.gov/sites/default/files/2023-10/FACT_SHEET_-English_-Pedestrian_and_Bicycle_Improvements_on_East_Cabrillo_Boulevard_and_Replacement_of_the_Union_Pacific_Railroad_Bridge_Project.pdf

http://www.sbroads.com/pdfs/phase4de_map_Oct_2023.pdf

[SeriesE]

Interesting to see that they are considering rebuilding to right hand ramps. Even if the left exit was closed without replacement, Cabrillo Blvd can still be accessed southbound via the Milpas Street exit.

[jlam]

Never seen anything like it before, why do the exits on 101 exit center and not on the right but the onramps do? Any background on this?

Ha, I accidentally took this exit in Santa Barbara last month. It wasn't very well signed, and the passing lane kinda just defaulted onto the exit. Construction was occurring at that spot, which didn't help. As for why the interchange is like that, no clue. I assumed the other ramps were added later, but nope, as far as I can tell, those other movements were there since the interchange was built.

[NE2]

The southbound bridge was part of a two-lane (or narrow four-lane?) US 101 with the Cabrillo Boulevard access hooking back around to it to the east. When US 101 was widened, the bridge was kept, and there was no room for ramps on the right side. The northbound exit was probably placed on the left to get some SPUI-ish advantages, while the northbound entrance was probably put on the right because left entrances were already known to suck. (There was also, as now, a northbound right exit at Hermosillo Road and a southbound right exit at Los Patos Way; the only forced left-side ramp was the southbound entrance that's now gone.)

[JustDrive]

^
I remember the left ramp onto SB US-101 from when I lived there in the '90s. It was always a tricky intersection.

Cabrillo Blvd. was part of CA-225 (former LRN 150) and provides direct access to the beach area so it made sense to connect it directly to US-101.

The project pages indicate that they intend to close the Los Patos exit (and RR undercrossing) and re-construct the Cabrillo interchange to be all right-hand ramps:

https://santabarbaraca.gov/sites/default/files/2023-10/FACT_SHEET_-English_-Pedestrian_and_Bicycle_Improvements_on_East_Cabrillo_Boulevard_and_Replacement_of_the_Union_Pacific_Railroad_Bridge_Project.pdf

http://www.sbroads.com/pdfs/phase4de_map_Oct_2023.pdf

I mean, they did the same at the Sheffield Drive ramps 1.5 miles east. The left-hand exit/entrance was removed and reconstructed in between the freeway and the bluff/railroad tracks.