Tram to/from parking lot safety recording

[cygnusx1jg]

Does anyone know approx when they started having the recorded safety message on the trams that take you from the parking lot to the main gates?

Also, I've noticed that if someone sneaks onto the tram while the message is being played, they are required to play it again in it's entirety.

Did any specific incedent happen or is this just Disney being very safety aware? Heck, for years the trams didn't even have doors on them.