Probably not the best time for a joke but here goes.
A new employee and his boss were working along the train tracks when the boss decided to quiz the new kid, so he asks him what he would do if he saw two trains headed at each other on the same track? The kid says he would run inside and call dispatch and tell them to stop the trains. Very good says the boss but what would you do if you couldn't get ahold of dispatch? The kid says he would run over and throw the track switch so the trains would miss each other. Excellent says the boss, but what would you do if the switch was stuck? The new kid thinks for a bit then says he would get on the phone and call his Uncle Joe. Your Uncle Joe, Why would you call him, what can he do asks the boss. Oh he can't do nothing says the kid, it's just that my Uncle ain't never seen a train wreck before.