MUTCD mileposts in California

[roadfro]

I was heading from Reno to Vegas yesterday and decided to take US 395 and cut over on SR 120 to US 6 for something different. When turning north on to US 6 from SR 120, I found that there are MUTCD standard mileposts along US 6, in addition to Caltrans standard postmiles. The mileposts were posted double-sided and mounted on the eastbound (northbound) side of the road. Along that stretch, the milepost count was about 8 miles higher than the Mono County postmiles.

I seem to remember some discussion on this forum about Caltrans doing a one-off experiment with MUTCD postmiles on some state highway (SR 58 comes to mind, but I'm not sure). I don't recall any discussion of them appearing anywhere else. Are there any other instances of MUTCD mileposts in California?

[agentsteel53]

Are there any other instances of MUTCD mileposts in California?

58 is the only one I can think of.

[myosh_tino]

It also seems that San Diego county uses these mileposts on their county routes.  The above photo is CR-S1 and is from the AARoads Gallery.  Does anyone know why San Diego county installed mileposts on the county routes?

Regarding CA-58, the mileposts were installed during the construction of the Mojave Bypass freeway.  Within a couple of years, the mileposts were extended west to just outside Bakersfield and east to the Kern-San Bernardino county line where CA-58 reverts back to a two-lane highway from a 4-lane freeway.

[agentsteel53]

Does anyone know why San Diego county installed mileposts on the county routes?

I couldn't tell you why but I do confirm that they are all over the entire county route system down here.  I somehow feel like there's a couple of green mileposts in Imperial county too, but I cannot recall specific details, so I might be making that up.

I know San Diego county influence extends into Imperial... at S80, there is an S2 shield marked "San Diego County" despite being about 5-10 miles into Imperial County.