fracturedfairfax Wrote:
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> That's Rock Hill, and there's a fairly serious
> drop between the west end of the curve, which has
> an elevation of 300 feet, and the east, which is
> only 250 feet.
>
> The straight-line distance between the two ends is
> only about 500 feet, so if you do a little
> calculation, a road that went straight through
> would have a grade of about 10%, which is unsafely
> steep.
>
> To improve the grade, you have two choices. Make
> the path longer by incorporating a long curve,
> which is what they did, or spend millions of
> dollars to artificially lengthen the grade with
> fill towards the Cub Run side on the east. They
> went with the cheap option.
>
> The road's been the shape it is for at least a
> hundred years: I checked both historical aerial
> imagery for 1937 and topographic maps to 1915, and
> both show the same curve. I suspect it's been that
> shape since the road was cut, and definitely since
> it was paved.
>
> Historic aerial imagery -
>
http://www.fairfaxcounty.gov/maps/photo.htm
> Historic topographic maps -
>
http://historicalmaps.arcgis.com/usgs/
Thank you!