Sometimes, you just wish you hadn't left your cattle prod at home.
Then, when you're riding the escalator to the subway, some fool gets off the escalator and stops walking. He* stands there, completely oblivious, often gazing about with wide-eyed incredulity and possibly drooling a bit.
You can tell such a person has never studied physics. If he had, he'd know that a person getting off the escalator behind them, travelling at a rate of 0.6m/s, with average mass, is going to transfer all 51kJ** of energy into them when they inevitably pile up. In November '06 several people were injured in a pile-up when someone fell on an escalator, some seriously.
If only I had my cattle prod with me; our physics-dropout fool would feel the wrath of 10,000 volts to the buttocks. In the interest of public safety, it's better to use a prod than something more gratifying like a taser (200,000 volts). The taser will incapacitate the dropout causing him to collapse on the spot, when what we want is to move him away from the escalator. Only when he's clear of the unloading zone is it safe to use that taser.
* Or she
** I used the fat-man average mass for this calculation, because of the obesity epidemic