Highway Enthusiasts - Why do 120 and 108 have "freeway sections" in random places?

Not sure if this question is something anyone will know, but I've always been curious as to why there's a full on freeway on highway 120 between Groveland and San Pedro reservoir. You can also see the bridge over the reservoir is obviously only half complete and has room for the other side of a freeway. Considering the Priest Grade, it's obvious there weren't plans to extend a freeway all the way to Yosemite, so I'm curious why it was built like that and when? Also, Highway 108 which is a really low traffic Sierra pass has a random freeway section as well near Pinecrest Lake in the forest and then goes back to 2 lanes. Any idea why both of these exist and what other plans may have existed?

The section between Chinese Camp and Moccasin was built new in 1970 when Lake Don Pedro was enlarged, so it's built to newer (i.e., faster) standards than the rest of the road. The bridge was built with the possibility of expansion because apparently much more traffic (to where??) was envisioned and it would be difficult to widen the bridge later, when the support was covered by 200' of water.

Not sure why 108 is freeway-like, but based on the width of the right of way, it appears there were plans to widen other sections as well.

Thanks for the history lesson. Since we're talking 120, I've always wondered about the section between the 108-120 junction and Chinese Camp. Right after you turn onto 120 from 108 there are two almost 90 degree turns near the railroad tracks and lumber yard. Anybody know the reason the road curves like that?

The freeway sections of 108 were originally built as part of a plan to have 4 lanes all the way to Dodge Ridge. They built the easy sections when they got funding, but have never solved the funding issues for the sections through Sugar Pine/Miwok Village. Those involve more purchase of private property along the way.

They added another section of freeway below Twain Harte in the last couple of years thanks to the TARP finding...

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Pretty sure the reason for the 90* turns is you want to have the highway to be perpendicular to the tracks at the crossing. To make this happen, two 90* turns were necessary.