How to decide if an aging parent should still be driving?

If you're asking, you must have some concerns. What is going on?

A little bit more information, or setting up your profile might help with answers. What warning signs are you concerned about? General age related decline? Signs of dementia?
There are a few articles and similar questions here filed under the driving topic. This article has a list of signs you might look for.
https://www.agingcare.com/articles/signs-elder-unsafe-driver-153264.htm