DOT



Helmet Testing Information

The following documents describe the testing methods used by the DOT to approve helmets. As you will see on Page 16 of the first document the impact requirements are as follows:
NOMINAL THEORETICAL MINIMUM
DROP HEIGHT IMPACT VELOCITY ACCEPTABLE VELOCITY
138.4cm (54.5 in) 5.2m/sec (17.1 ft/sec) 4.94m/sec (16.23 ft/sec)
182.9cm (72.0 in) 6.0m/sec(19.7 ft/sec) 5.70m/sec (18.72 ft/sec)

So with 1 foot / second = 0.681818182 mph then the highest Theoretical Impact Velocity is 13.43 MPH. (19.7 ft/sec * 0.681818182)

http://www.nhtsa.dot.gov/cars/testing/procedures/TP-218-04a.pdf

http://www.nhtsa.dot.gov/cars/testing/procedures/TP-218-04b.pdf