16% Road incline!

paulj wrote:
But as one who grew up in the mountains, a true switchback is one where a pickup has to execute a 3 point (or more) turn, the equivalent of turning around in the middle of a city street. The only paved route that I've encountered like that is in Yoho Nat Park (BC). One pair of curves is signed, telling vehicles longer than 7 meters (21 ft) to back up the middle leg.

:E:E:E

It's not a highway but a campsite road that can only hold one truck and on one side is a deep ravine.

Fortunately, those who traverse this road know the road protocols and are thoughtful.

California has a number of state highways that are restricted by length, either total length or 'kingpin' length. It's curvature that's the issue, though curves usually go along with grades. In fact the worst grades are on the inside of sharp curves. I'm thinking in particular of Sonora Pass (108). I know of some city street intersections like that in the Seattle area.

Many of those California roads were originally wagon tracks, and due to terrain and usage have not seen much change in route or grade. CA162 (Lone Pine) follows a dry (usually) steam bed, crisscrossing it without bridges or culverts, and minimum of cut and fill.

RV posters often worry about switch backs. But as one who grew up in the mountains, a true switchback is one where a pickup has to execute a 3 point (or more) turn, the equivalent of turning around in the middle of a city street. The only paved route that I've encountered like that is in Yoho Nat Park (BC). One pair of curves is signed, telling vehicles longer than 7 meters (21 ft) to back up the middle leg.

Yosemite Sam1 wrote:
So the 6% max grade are only for freeways?

Applies to all roads receiving federal funding, which typically includes most state, US and I routes (and in some cases city and county routes).

BUT!!!! There is a "design exception" process. In some cases, it's not possible or reasonable to meet federal design standards. As part of the process, we review the safety, capacity, delay and assess what it would take to meet the design standard.

For some of these routes, you would have to dig out a canyon hundreds, even thousands of feet deep for miles or dig long tunnels at many millions of dollars. It's pretty easy to justify a design exception.

These are mostly low volume, low speed roads with little commercial traffic. They mitigate via signing and prohibiting certain vehicle types.

naturist wrote:

paulj wrote:
High Bar road descending into the Fraser Canyon, British Columbia, has 23% grade sign at the top.

Half way down I stopped for a breather. The front wheels (on my suv) were too hot to touch.

The Hill to Bella Coola is only 10-11%, but longer. I've seen a pickup camper with a brake fire at the bottom.

Those, my friend, are why God gave us lower gears.

Burned my brakes at Tioga Pass in downhill descent even with the lowest of gears as the RV is pushing the trailer puller. Had to as I was afraid it will in turn ruin the gears iff it goes beyond the prescribed speed limit (better minds and experts may chime in if my fears are unfounded).

Almost easier on a dirt road as then 4LO is available. Could be other issues if towing.

paulj wrote:
High Bar road descending into the Fraser Canyon, British Columbia, has 23% grade sign at the top.

Half way down I stopped for a breather. The front wheels (on my suv) were too hot to touch.

The Hill to Bella Coola is only 10-11%, but longer. I've seen a pickup camper with a brake fire at the bottom.

Those, my friend, are why God gave us lower gears.

You can find them if you look but why? I thought interstates were limited as to how much incline they could have.

High Bar road descending into the Fraser Canyon, British Columbia, has 23% grade sign at the top.

https://xpedbc.com/2017/08/27/time-travel-in-the-cariboo/

Half way down I stopped for a breather. The front wheels (on my suv) were too hot to touch.

The Hill to Bella Coola is only 10-11%, but longer. I've seen a pickup camper with a brake fire at the bottom.

Rennell Sound road on Haida Gwaii has 24% grade at the bottom

http://britishcolumbia.com/plan-your-trip/regions-and-towns/northern-bc-and-haida-gwaii/rennell-sound/

Long Canyon in Utah (near Dead Horse State Park, Moad) is a good for testing your brakes or low-range.

https://www.dangerousroads.org/north-america/usa/6502-long-canyon-road-pucker-pass.html

6% is the general limit for interstates. I70 has some 7% up to the tunnel. Could be some others but not many.

When I was young I rode my bike up the east side of Sonora with a buddy. Scary was coming back down.

PA 487 between Ricketts Glen State Park & Red Rock, PA includes a 2 mile 18% grade.