While EPAMD and Segway have been used interchangeably by many, most states and the Fed impose the following key restrictions on what constitutes one:
- two non-tandem wheels
- max speed somewhere between 25 and 12.5 mph
- with that generally conforms to that of a hover round or 'fatty' wheelchair
- designed for one user
- sometimes you'll see an HP limit which is usually 3
- the device must be self-ballancing
- often you'll see a reference to movement being controlled by leaning
Basically, the rules were created for Segways but had to be made without referring to the brand, thus a need for a non-pattented term was created and EPAMD has become the consensus.
Almost all Segway clones are EPAMD devices and if they don't quite meet the definition a court will likely determin that the other device conforms with the spirit of the definition.