I feel like it's extremely misleading to give this example without providing surrounding context.
"Route 66" in this area is a 70 mile, parallel road to I-40 that serves a population of zero or nearly so and is a 2 lane strip of asphalt through the desert left over from before I-40 was constructed. It serves basically no function and no population, today.
It's not very obvious at all that it makes sense to spend money replacing the 100+ timber bridges along the stretch rather than just abandoning most of the road/downgrading it to a 4WD road with no bridges - although repairing/rebuilding it does seem to be what San Bernadino County hopes to eventually do.
Many of the bridges, while partially failing due to age, are also failing due to flooding damage - which is what caused the 3 ton weight restrictions to go in place in the first place and the sections that have been closed since 2014/2017.
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Additionally, the road is only officially closed east of Kelbaker Rd, and that section of road has zero population, and there's basically zero regional significance to the closure beyond mildly inconveniencing a few people in Amboy who can now only go West to get to I-40/civilization. (Especially since most reports I've seen suggest you can continue to the unpaved/rarely traveled Cadiz Rd anyway, which was the only connection that could only be accessed from the closed section).
The road from Ludlow to the Dish Hill Volcano is open, just less convenient if you used to get to it from the East.
Citation: https://dpw.sbcounty.gov/operations/road-closures/