This interchange in the Bay Area is pictured in the Wikipedia page for "Banked turn."
https://goo.gl/maps/XC4RATu5N7VkvQfh8
What is the greatest angle of banking on a numbered highway in the US or Canada?
For Canada, the current TAC puts the maximum superelevation at 6%. I've seen some old 1980s and older manuals make mention of 8% but never heard of it actually being built. The earth fill on the backside and the length of the run out would somewhat defeat the advantage that the tighter radii would offer. Not saying it can't be done, especially in older urban freeways. Just never heard of it.
The ramp from wbd M-8 to nbd M-10 in Highland Park, MI (https://goo.gl/maps/g95eEJEiW2EgV7Gh7) is fairly tight but can be taken at near 55 mph.
The pre-World War II German Autobahnen were designed with maximum superelevation (emax) of 8%. Per an article in the 1942 issue of Proceedings of the Highway Research Board, some elements of the Pentagon road network were built with emax of 10%. Proposed 1944 standards for the Interstates called for emax of 12%, reduced to 8% in areas where snow or ice could be expected. I do not think I have ever seen a design reference or a proposed set of design standards calling for superelevation greater than 12%, though I understand the French (who occupied Morocco at the time) used values as high as 20% for the Salé-Meknès road in the 1920's.
If you are designing to a given level of side friction demand at a given design speed, with superelevation taking up a set fraction of the total centripetal acceleration keeping the vehicle on the road (as is often, but not universally, the case--the US is one large exception to this), you generally obtain a more forgiving result if you reduce emax and increase minimum radius to compensate. The reason for this is that centripetal acceleration increases with the square of speed, while it decreases with radius. Thus, speed a set amount (say 20 MPH) above design translates into higher side friction demand the higher emax is. This is also borne out in accident experience--the curve of accidents per VMT versus curvature has a "knee" between 2° (2865 ft) and 3° (1910 ft).
CA-108 has some 26% grades as you near Sonora Pass. There are some extremely steep curves.
The picture shown in the original post confirms that these sound like a good idea until you take dead stopped traffic into account.
Most likely not the steepest overall, but I-90 in Downtown Cleveland (https://goo.gl/maps/yXy5x8bN7JWfFrHD9)is one of the more notable ones on an interstate highway. 35 mph advisory speed, and view partially obstructed by the OH 2 overpass going eastbound.
Quote from: SkyPesos on August 29, 2023, 07:43:59 PM
Most likely not the steepest overall, but I-90 in Downtown Cleveland (https://goo.gl/maps/yXy5x8bN7JWfFrHD9)is one of the more notable ones on an interstate highway. 35 mph advisory speed, and view partially obstructed by the OH 2 overpass going eastbound.
Not very well banked and the drainage sucks. Barely got through there in a rainstorm recently. Felt like 8" of standing water on the left side of EB lanes.
I'm not sure if this is steep enough to match the spirit of the thread, but this one north of Denver (https://www.google.com/maps/@39.9998184,-104.9809356,3a,52.6y,13.32h,90.82t/data=!3m6!1e1!3m4!1sGXudqggv2l-b5-kSFentPQ!2e0!7i16384!8i8192?entry=ttu) stands out to me for the Front Range. The bank fits well here; I don't think I've ever seen it backed up too horribly.
Don't know what angle it's banked, but I used to take the ramp from NB SH 289 to EB US 82 going to work with little slowdown. 65 was good but 70 was pushing it.
There is one along US 211 in Shenandoah National Park west of Skyline Drive. The road is pretty winding down the Blue Ridge Mountain into Luray. Don’t know the angle of it, but it’s has a good radius built for 45 mph navigating.
Quote from: jlam on August 30, 2023, 01:56:50 AM
I'm not sure if this is steep enough to match the spirit of the thread, but this one north of Denver (https://www.google.com/maps/@39.9998184,-104.9809356,3a,52.6y,13.32h,90.82t/data=!3m6!1e1!3m4!1sGXudqggv2l-b5-kSFentPQ!2e0!7i16384!8i8192?entry=ttu) stands out to me for the Front Range. The bank fits well here; I don't think I've ever seen it backed up too horribly.
Correct me if I'm wrong - That's the 168th/CO 7 exit, right? That used to be, where we defined the start of Denver when I was a kid. Before expansion, this was where I-25 went from 4 to 6 lanes. I don't know that I'd call that a 'steep' bank, but it's definitely there.
I would also submit, 287, at the north end of the Laporte Bypass (where it intersects 54G). The intersection is on a curve, and I can remember sliding sideways down it when turning on ice once.
This is fun to come to northbound, though. The express lane ends shortly south of here, and all those cars that whizzed by me at 80 in it, while I was stopped in the free lanes, now have to make the Merge of Shame.
It's not there anymore since they rebuilt it, but the offramp from SB 25 to EB 76, used to be a tight, 15mph curve with a pretty short decel lane before it. That one, you felt like you were on two wheels going around.
Steepest turn on a numbered highway, tho? Well, the Mt Evans road is a numbered road (CO 5), and I would submit any of the switchbacks toward the top, as beeing steep, banked, and generally just scary.
One of the steeper banks I'm aware of, on a mainline, is 95 North in Delaware after the 295 split before the 495 split. From the roadway itself, it doesn't appear too bad: 5 lanes wide, along with 2 shoulders, in a sweeping curve.
https://maps.app.goo.gl/g39ujisDvXmsFDvY8 . When you're under it though, you realize how steep that curve is.
https://maps.app.goo.gl/4ZqaEQg9rrr1T6iu5 .The pillars on the right are nearly 6 feet taller than the pillars on the left.
^
Speaking of 495's, this reminded me of the Capital Beltway between exits 31 & 33 where it winds along Rock Creek. The superelevation is easily noticeable, and the median design around the bend shows the elevation difference between the inner loop & outer loop.
https://www.google.com/maps/@39.0141027,-77.0614815,3a,43y,238h,86.82t/data=!3m6!1e1!3m4!1sqhz7vxc3bSLX-xsxBsy8-g!2e0!7i16384!8i8192!5m1!1e1?entry=ttu
https://www.google.com/maps/@39.013192,-77.0625015,3a,75y,54.43h,85.34t/data=!3m6!1e1!3m4!1seNY8LlMzvNzsNYr9bP-jrg!2e0!7i16384!8i8192!5m1!1e1?entry=ttu
https://www.google.com/maps/@39.0065722,-77.0687909,3a,75y,76.27h,89.97t/data=!3m6!1e1!3m4!1smV4b9xEC9DXHTOavQYCJ5Q!2e0!7i16384!8i8192!5m1!1e1?entry=ttu
https://www.google.com/maps/@39.0075137,-77.0678585,3a,75y,217.96h,86.93t/data=!3m6!1e1!3m4!1s2fAgzS8MEqmMFMJTgfGS8A!2e0!7i16384!8i8192!5m1!1e1?entry=ttu
SR 528 over John Young Parkway in Orlando.
https://goo.gl/maps/BHmecWYyBYjVSwEn6
Look at the overpass carrying the 528 freeway and the angle of it.
Well, as long as the superelevation is less than that on the turns at the NASCAR track at Daytona Beach, FL, I'm happy.
:nod:
Mike
Apparently the highest superelevation normally allowed in the US is 12% (https://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/chapter3/3_superelevation.cfm), and the local trumpet interchanges I measured in Google Earth did reach it:
US-30E to WA-433 (155ft radius and 20-25mph advisory speed) and US-26 to US-101S (145ft and 25mph):
(https://i.imgur.com/JqO4YRL.jpg)(https://i.imgur.com/dLM6FeL.jpg)