Requiring curbing on a 3% grade is too low and unnecessary. It's challenging to even see a 3% grade while parked and a grade of this magnitude does not actually present a significant threat to runaway cars. A grade this low seems to be a trap designed to generate revenue for the city.
San Francisco Director of Transportation, Edward D. Reiskin
Increase the threshold for ticketing cars on inclines for not curbing their cars from 3% to 10%