The workers know pretty well about safety and hazards of the third rail; its part of their initial job training.
Kids, on the other hand, are a different story. I was born and raised in the city of New York and when I was growing up I learned about the dangers of the third rail was by simply observing it. I remember watching subway trains go by and noticing the very large sparks the third rail sometimes emitted when a train went by. I knew therefore that it would be a very bad idea to go near the third rail, let alone the tracks. But unfortunately some kids and teens don't learn. Even when they do know about the dangers, they are in denial that something bad will happen to them and next thing you know, they are either dead or on a one way ticket to the hospital.
Same goes for some Adults. They are late to work or just don't have patience and they see their train on the opposite platform. Instead of taking the walkway over to the other platform, they climb down on the tracks and try to make it to the other side this way. Well sometimes because they are in such a rush to make it to the other side, they are not cautious of the tracks so they trip or slip and their body comes somehow in contact with the third rail. Its a shame.
I don't have a source for this, but I would say its somewhere in the neighborhood of 2-13 people a year just from the third rail in just the NYC Subways. Now the national average is higher. I also think third rail casualties and fatalities cause for about 10% of all electrified trains.
I should start giving stars for safety questions too. Here's yours.