San Antonio Valley Road
A remote link between Mount Hamilton and the Mines Road junction, with exposed bends and ranchland.
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Road shape
- Length
- 16.1 mi
- Bends
- 97
- Switchbacks
- 18
- Bends per mile
- 6
- Turning per mile
- 647°
- Curviest rank
- 34of 85
Measured from the OpenStreetMap centreline at a 20 m sampling step — road shape only, not a safety or speed judgement. How bends are counted.
Elevation
- Total climb
- 3,154ft
- Climb per mile
- 196ft
- Highest point
- 3,558ft
- Steepest grade
- 9.3%
Sampled every 100 m from USGS 10 m elevation data, a public-domain federal dataset. Total climb counts vertical change in both directions, so it does not depend on which way you drive. How elevation is measured.
Speed limits
Varies
Unverified
Check posted signs along the road.
No reliable posted limit was found for this road. Check signs along the route.
Posted signs always govern. How speed evidence is handled.
Sources
Difficulty 3/3 (Demanding) is our editorial rating of width, bends and sightlines; “Technical” describes character, not a target speed. Full method. Identified from:
- r/bayarea · Marin driving roads ↗
- OpenStreetMap road data ↗ (15 ways in this trace)
Reviewed 2026-09-08. The trace shows selected road sections, not a navigation route.