oh ok, i usually just stop riding when i see them coming and when they tell me I can't ride there i just say, "pshh me jump that on my scooter, are you crazy, i would kill myself." then they just say okay and walk away, works every time
He probably doesn't mean they will literally shatter, but it probably hurts really bad, i would suggest filing down the sides with a dremel or a metal file
http://www.scooterresource.com/forum/showthread.php?t=75389
Here is another thread about this, use the search bar next time, it was only one page over.