Just in case, I contacted tech support for my planner. They said the routing engine thinks I'm a commercial vehicle and those roads are closed to commercial vehicles.
That and some poor photo interpretations on the web led me astray.
Rick,
2019 Grand Design Reflection 150 273MK 2015 Ford F350 CC SB Lariat Powerstroke PullRite Superglide
We pulled this both ways on 123 between U.S. 12 and 410 last year as we stayed at The Dalles Campgound for a few nights. Didn't have any problems other than some rough stretches of pavement.
From the website, says 13.1 so you should be OK, not sure if you would have to drive down the middle which would be a concern. It does say, no commercial vehicles.
I would ask, why are you going that way? I have looked at state campgrounds in the area and depending on the size of your trailer, you might not be able to get a spot that can accommodate. That is the reason we found bumping lake. There are some nice areas to camp off Hwy 12 and some off 410, but didn't have a reason to take 123 to connect them. However, glad I now know about that tunnel. I will avoid that if pulling my 5th wheel. I'm sure it is marked at both ends of the highway.
I've driven the distance of 410 from Enumclaw to Yakima with our 5th wheel and have never experienced a problem. We camp near the Crystal cutoff and have camped at Bumping lake a few times, no issues with height.
Not sure about 123, haven't gone that way. I have driven hwy 12 with no issues for height.