Grab a new ball
Players can substitute a new ball in place of an old ball anytime they take relief under any circumstance, even free relief. Under the old rules, a player could put a new ball in play when taking penalty relief from a hazard, for example, but not when taking free relief from an obstruction.
The USGA said the new rules clear up any confusion about when a player can replace a ball, especially in cases in which a player can identify their ball but not necessarily recover it.
So starting in 2019, if you take relief from a cart path, feel free to put a new ball in play.