Will,
Sorry to say this but that very thing has been happening right here in the US every year since August 1916!! The annual Pikes Peak International Hill Climb is held just outside of Colorado Springs, Colorado. About an hours drive south of Denver. No spectator stands only ropes and dirt berms separate the the crowds from the cars. Barriers are found in a few places along the track but not many.
The racers historically are a who's who in auto racing from all over the world and especially here in the US. Including the Unser family which is the winningest family on the Hill climb. The eldest family members started racing it in 1926. Roger Mears has also won, as have many other notorious and popular drivers both men and women.
Vehicles range from motorcycles to modified Rigs (we're talking Kenworth's and Freightliners) to purpose built open class cars!
The greatest and most exciting race I have ever been to in my life as a spectator! Hands down!
The race is dubed the Race to the Clouds!
Website for the Pikes Peak International Hill Climb (with photos)
http://www.ppihc.com/default.aspx?tabid=1
Just some stats of the track:
Length 65,560 feet or 12.42 miles
Width -
straight 20 feet
curves20 to 50 feet
Surfacegravel/asphalt
Elevation at Start - 9,402 feet
Elevation at Finish - 14,110 feet
Elevation gain - 4,708 feet
Length of plus grade61,626 feet - maximum plus10.5%
Lengh of negative grade3,934 feet - maximum negative10.0%
Average grade 7%
Ceasar