I'm an engineer..

Three engineers and three accountants are
traveling by train to a conference. At the
station, the three accountants each buy tickets
and watch as the three engineers buy only a single
ticket. "How are three people going to travel on
only one ticket?" asks an accountant. "Watch and
you'll see," answers an engineer. They all board
the train. The accountants take their respective
seats but all three engineers cram into a restroom
and close the door behind them. Shortly after the
train has departed, the conductor comes around
collecting tickets. He knocks on the restroom door
and says, "Ticket, please." The door opens just a
crack and a single arm emerges with a ticket in
hand. The conductor takes it and moves on. The
accountants saw this and agreed it was quite a
clever idea. So after the conference, the
accountants decide to copy the engineers on the
return trip and save some money (being clever with
money, and all). When they get to the station they
buy a single ticket for the return trip. To their
astonishment, the engineers don't buy a ticket at
all. "How are you going to travel without a
ticket?" says one perplexed accountant. "Watch
and
you'll see," answers an engineer. When they board
the train the three accountants cram into a
restroom and the three engineers cram into another
one nearby. The train departs. Shortly afterward,
one of the engineers leaves his restroom and walks
over to the restroom where the accountants are
hiding. He knocks on the door and says, "Ticket,
please."