Mount Diablo roads
The north and south approaches converge on the summit road. Park access and hours apply.
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Road shape
- Length
- 17.8 mi
- Bends
- 173
- Switchbacks
- 43
- Bends per mile
- 9.7
- Turning per mile
- 1107°
- Curviest rank
- 7of 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
- 5,184ft
- Climb per mile
- 291ft
- Highest point
- 3,816ft
- Steepest grade
- 8.3%
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
15–25 mph
Mapped limits
Approximate guide; limits vary by section. Follow posted signs.
OpenStreetMap tags cover approximately 87% of this trace. These values have not been checked against current signs.
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:
- Driver’s Guide · Regional road directory ↗
- OpenStreetMap road data ↗ (24 ways in this trace)
Reviewed 2026-09-08. The trace shows selected road sections, not a navigation route.