The first time you drive your parents somewhere instead of the other way around, notice it. Roles quietly switch.

Big changes inside a family almost never get announced. One day you have the keys and somebody who used to drive you is in the passenger seat giving directions you do not need, and the entire arrangement has shifted with no conversation about it. Most of the important transitions look like a Tuesday errand.

When one of those moments happens, say something about it, even just that you noticed. Offer the next drive before anybody asks you. Taking a turn early is a much easier way into this than having it land on you all at once later.