Is it true that the requirement on helmets is that they be able to withstand direct impact at just 14.5 miles/hour?
That's a little simplified: the actual TEST(S) involve multiple strikes on helmets for both penetration (a pointed striker) flat solid surface tests (dropped on a flat anvil with a headform inside) and curved solid surface tests (dropped on a curved anvil with a headform inside)...and multiple strike tests, where the helmet is re-subjected to strikes in the same area( to simulate your head bouncing along the road).
The MPH figures are deceiving: Fatal head injuries occur in the 7mph range (yep, truth). That's how fast your head would contact a solid surface at a drop from 4ft, unimpeded to a curved or pointed surface (like a rock). The fact is that you have to take into account how most bike accidents happen, and then factor in how most motorcycle head injuries occur to determine reasonable standards for helemt construction.
The old Snell standards were developed for racecar drivers, who were subjected to different types of headstrikes than bikers.....bikers were dying with incorrectly constructed Snell helmets. New Dot, Snell, and Ansi specs take into account the difference in motorcycle on auto accidents.
The mean speed motorcycle accidents occur at is 21 mph. Unless you suffer direct contact with your head (horizontal speed, NOT verticle speed) to a solid (like a brick wall....contact with an auto will be different because sheetmetal and plastic deform, absorbing energy) object, the helmet will most likely do it's job.
The problem with guys like "Tattoo Jesse" is that they never paid attention in physics class; (they were out smokin' a joint in the boys bathroom during the lecture on thermodynamics) therefore when they hear "14 mph" they only focus on that one small piece of info, not knowing that your helmet can absorb TWICE the lethal dose of kenetic energy (E=Mass*Velocity) in a single strike....much more if you calculate multiple strikes.