OT: How are EPA Mileage standards calculated ?

[Grateful11]

The only vehicle we've had that we could not get what the EPA rated them at was an '04
Explorer it really sucked gas and quality wise. My Scion xA was rated at 38 and I get 38 to
my newest recent high of 42.9mpg. The new standards are rated for the way idiots drive,
they dart in and out of traffic and have the foot working that gas pedal like a bass drum.