Blizzard updated elevators in Overwatch PTR in hopes of making them a more reliable escape route. Elevators have functioned roughly the same since Overwatch first released in 2016. They endlessly loop, going up and down even if no one is around to use them.
Blizzard has decided to change that, "Elevators will now wait at the bottom of their track until a player boards the platform. After a short delay, the platform rises rapidly upward. Once the elevator reaches the top, it pauses briefly before returning to the bottom."
Based on the developer comments, the team heard feedback by the players expressing their frustration in waiting for the elevator to return down, especially in the midst of a battle. There is nothing worse than trying to escape a raging Reinhardt, and you're stuck waiting for the elevator to return.
These new changes will give certain heroes a decent chance at escape on certain maps, that is, if you're not facing a Pharah, Genji, or the many other heroes that can get on top of a building, no problem.